Combined Spectroscopic and Quantum Chemical Study of [trans-ru(c CC 6 H 4 R 1 -

Combined Spectroscopic and Quantum Chemical Study of [trans-ru(c CC 6 H 4 R 1-4) 2 (dppe) 2 ] n+ and [trans-ru(c CC 6 H 4 R 1-4)(C CC 6 H 4 R 2-4)(dppe) 2 ] n+ (n = 0, 1) Complexes: Interpretations Beyond the Lowest Energy Conformer Paradigm. Santiago Marqués-González, Matthias Parthey, Dmitry S. Yufit, Judith A.K. Howard, Martin Kaupp,*, Paul J. Low *,, Department of Chemistry, Durham University, South Rd, DH1 3LE, Durham (UK) Technische Universität Berlin, Institut für Chemie Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin (Germany) New permanent address: School of Chemistry and Biochemistry, University of Western Australia, 35 Stirling Highway, Crawley, 6009, Perth (Australia) 1

LIGAND SYNTHESIS All reactions were carried out in flame-dried glassware under an oxygen-free nitrogen atmosphere using standard Schlenk techniques. Triethylamine was purified by distillation from CaSO 4, other reaction solvents were purified and dried using Innovative Technology SPS-400 and degassed before use. The catalyst Pd(PPh 3 ) 4 was prepared by literature methods. 1 Other reagents were purchased commercially and used as received. NMR spectra were recorded in deuterated solvent solutions on Bruker DRX-400 and Varian Inova 300, 400, 500 spectrometers and referenced against solvent resonances ( 1 H, 13 C). ESI mass spectra were recorded using a TQD mass spectrometer (Waters Ltd, UK). Samples were (1 mg/ml) in analytical grade methanol. ASAP mass spectra were recorded from solid aliquots on an LCT Premier XE mass spectrometer (Waters Ltd, UK) or Xevo QToF mass spectrometer (Waters Ltd, UK) in which the aliquot is vaporized using hot N 2, ionized by a corona discharge and carried to the TOF detector (working range 100-1000 m/z). Matrix assisted- Laser Desorption/Ionisation (MALDI) mass spectra was obtained using an Autoflex II TOF/TOF mass spectrometer (Bruker Daltonik GmBH) using a trans-2-[3-(4-tertbutylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) matrix. Infrared spectra were recorded from CH 2 Cl 2 solutions and nujol mulls on CaF 2 plates. Preparation of 4-bromo-(trimethylsilylethynyl)benzene. 2 To a 500 ml round Schlenk flask charged with NEt 3 (250 ml) immersed in ice, 4-iodo-bromobenzene (18.05 g, 63.80 mmol), Pd(PPh 3 ) 4 (1.85 g, 1.60 mmol) and CuI ( 0.30 g, 1.6 mmol) were added. To the cooled solution trimethylsilylacetylene (11.0 ml, 7.51 g, 76.5 mmol) was added drop wise. The mixture was stirred in an ice bath for 8 h. Upon completion of the reaction the brown suspension was taken to dryness under reduced pressure and the residue was purified by silica gel column chromatography (hexane). Removal of solvent from the main fraction yielded a colourless oil that crystallized on standing. Yield 15.9 g, 62.8 mmol, 99%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.43 (d, J = 9 Hz, 2H, c), 7.32 (d, J = 9 Hz, 2H, b), 0.24 (s, 9H, g). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 133.5, 131.6 (b/c), 122.9, 122.3 (a/d), 104.0 (f), 95.7 (e), 0.0 (g). MS + (ASAP) m/z (%): 505.9 (100, [2M-2H] + ); 253.9 (41.8, [M] + ). IR (nujol) cm -1 : 2159 (s) ν(c C). 2

Preparation of ((4-(3,3-dimethylbut-1-yn-yl)phenyl)ethynyl)trimethylsilane. To a 100 ml oven-dried Schlenk flask charged with ((4-bromophenyl)ethynyl)trimethylsilane (2.53 g, 9.99 mmol), Pd(PPh 3 ) 4 (0.60 g, 0.52 mmol) and CuI ( 0.30 g, 0.52 mmol) in NEt 3 (100 ml), 3,3-dimethylbut-1-yne (1.53 ml, 1.02 g, 12.4 mmol) was added. The mixture was stirred at reflux overnight. The brown suspension was filtered and the red filtrate taken to dryness under reduced pressure. The residue was purified through a silica gel column using hexane as eluent. The pure product was obtained as an off-white powder upon solvent evaporation of the main fraction. Yield 2.16 g, 8.49 mmol, 85.4%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.37 (d, J = 9 Hz, 2H, g), 7.31 (d, J = 9 Hz, 2H, f), 1.32 (s, 9H, a), 0.25 (s, 9H, k). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 133.8, 131.5 (e/h), 122.4, 122.1 (i/j), 105.0, 100.7, 95.6 (d/i/j), 79.0 (c), 31.1 (a), 28.2 (b) 0.1 (k). Preparation of 1-(3,3-dimethylbut-1-yn-1-yl)-4-ethynylbenzene. To a 250 ml round bottomed flask charged with a solution of methyl ((4-(3,3-dimethylbut-1-yn-1- yl)phenyl)ethynyl)trimethylsilane (1.5 g, 5.9 mmol) in MeOH/THF (1:1) (100 ml), K 2 CO 3 (0.83 g, 6.0 mmol) and the suspension was stirred at room temperature overnight. The solution was then filtered and the filtrate taken to dryness under reduced pressure. The resultant black oil was re-dissolved in Et 2 O (50 ml) and washed with water (2 50 ml) and brine (1 50 ml) and dried over MgSO 4. Removal of solvent yielded the pure product as a yellowish oil. Yield 1.0 g, 5.5 mmol, 93%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.39 (d, J = 9 Hz, 2H, g), 7.56 (d, J = 9 Hz, 2H, f), 3.13 (s, 1H, k), 1.31 (s, 9H, a). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 132.0, 131.6 (f/g), 124.9, 121.1 (e/h), 100.9, 83.6, 78.9, 78.4 (c/d/i/j), 31.1 (a), 28.2 (b). IR (cast) cm -1 : 3291 (m) ν(c C-H); 2236 (m); 2192 (w) ν(c C). Preparation of 2-methyl-4-(4-((trimethylsilyl)ethynyl)phenyl)but-3-yn-2-ol. 3 To a 500 ml Schlenk flask immersed in an ice bath and charged with NEt 3 (450 ml), 1-bromo-4- iodobenzene (30.01 g, 106.1 mmol), Pd(PPh 3 ) 4 (6.12 g, 5.30 mmol) and CuI (1.01 g, 5.30 mmol) were added. To the cooled suspension, trimethylsilylacetylene (16.5 ml, 11.4 g, 116 3

mmol) was added in small portions over an hour. After stirring the solution at 0 ºC for 6 h, trimethylsilylacetylene excess was removed under reduced pressure keeping the reaction vessel in the ice bath. After refilling the vessel with N 2, 2-methyl-3-butyn-2-ol (11.3 ml, 9.81 g, 116 mmol) was added and the reaction mixture was taken out of the ice bath and heated at reflux overnight. The reaction mixture was then taken to dryness under reduced pressure, and the resulting black residue was re-dissolved in CH 2 Cl 2 and adsorbed onto silica for further silica gel column chromatography (hexane). The pure product was collected upon solvent evaporation of the main fraction as a yellow powder. Yield 21 g, 83 mmol, 78 %. 1 H NMR (400 MHz, CDCl 3 ) δ 7.37 (d, J = 9 Hz, 2H, e), 7.31 (d, J = 9 Hz, 2H, f), 1.32 (s, 6H, k), 2.01 (s, 1H, l), 0.25 (s, 9H, a). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 131.8, 131.5 (e/f), 123.0, 122.9 (d/g), 104.7 (b), 96.2, 95.8, 81.8 (c/h/i), 65.7 (j), 31.51 (k), 0.0 (a). MS + (ASAP) (m/z) 241.10 (100, [M-OH] + ). Preparation of 1-ethynyl-4-(trimethylsilylethynyl)benzene. 3 A 250 ml round bottom flask, fitted with a nitrogen purge, reflux condenser and bubbler was charged with sodium hydroxide (0.63 g, 0.16 mmol), 2-methyl-4-(4-((trimethylsilyl)ethynyl) phenyl)but-3- yn-2-ol (3.25 g, 12.6 mmol) and anhydrous toluene (150 ml). The solution was heated at reflux for 30 min whilst nitrogen was bubbled through it. Upon completion of the reaction, the red solution was poured into water, and the organic phase was washed with water (2 150 ml) and brine (1 150 ml), and dried over MgSO 4. The solvent was removed under reduced pressure and the residue was purified by silica gel column chromatography using hexane:ch 2 Cl 2 (9:1) as the eluent. Removal of solvent from the main fraction yielded the pure product as a white solid. Yield 1.83 g, 9.23 mmol, 73%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.41 (s, 4H, e/f), 3.16 (s, 1H, j), 0.25 (s, 9H, a). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 132.1, 132.0 (e/f), 123.7, 122.2 (d/g), 104.5 (b), 96.6 (c), 83.3 (h), 79.1 (i), 0.0 (a). MS-ASAP + (m/z) 183.05 (100, [M-CH 3 ] + ), 198.07 (24.4, [M] + ). IR (nujol) cm -1 : 3311 (s) ν(c C-H); 2159 (s) ν(c C). Preparation of methyl 4-((trimethylsilyl)ethynyl)benzoate. 4 To a 250 ml Schlenk flask charged with methyl 4-iodobenzoate (10.2 g, 38.9 mmol), Pd(PPh 3 ) 4 (2.24 g, 1.94 mmol) and CuI ( 0.369 g, 1.94 mmol) and NEt 3 (200 ml), trimethylsilylacetylene (7.0 ml, 4

4.8 g, 48.9 mmol) was added. The mixture was stirred at room temperature overnight. The mixture was taken to dryness under reduced pressure and the residue was purified through a silica gel column using hexane:ch 2 Cl 2 (8:2) as the eluent. Removal of solvent from the main fraction yielded an off-white powder. Yield 8.01 g, 34.5 mmol, 89%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.89 (d, J = 9 Hz, 2H, f), 7.47 (d, J = 9 Hz, 2H, e), 3.85 (s, 3H, i), 0.20 (s, 9H, a). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 166.5 (h), 132.0, 129.5 (e/f), 129.8 (g), 127.9 (d), 104.2, 97.8 (b/c), 52.4 (i), 0.0 (a). MS + (ASAP) (m/z) 464.19 (100, [2M] + ), 233.10 (70, [M+H] + ). IR (nujol) cm -1 : 2162 (m) ν(c C); 1732 (s) ν(c=o). Preparation of methyl-4-ethynylbenzoate. 5 To a solution of methyl 4- ((trimethylsilyl)ethynyl)benzoate (8.10 g, 34.9 mmol) in THF (150 ml), tetra-nbutylammonium fluoride (TBAF) (1 M in THF, 35.0 ml, 35.0 mmol) was added yielding an orange solution that was stirred at room temperature overnight. The solution was then taken to dryness under reduced pressure and the resultant black oil was purified through a silica gel column using hexane:ch 2 Cl 2 (1:1) as the eluent. Removal of solvent from the main fraction yielded the pure product as a yellowish powder. Yield 4.77 g, 29.8 mmol, 85.4%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.99 (d, J = 9 Hz, 2H, f), 7.56 (d, J = 9 Hz, 2H, e), 3.92 (s, 3H, i), 3.23 (s, 1H, a). 13 C { 1 H} NMR (101 MHz, CDCl 3 ) δ 166.5 (h), 132.2, 129.6 (e/f), 130.3 (g), 126.9 (d), 82.9, 80.2 (b/c), 52.4 (i). MS + (ASAP) (m/z) 320.10 (68, [2M] + ), 161.05 (27, [M+H] + ). IR (nujol) cm -1 : 3244 (s) (C sp H); 2104 (w) ν(c C); 1700 (s) ν(c=o). Preparation of 4-(trimethylsilylethynyl)aniline. 6 In a 100 ml Schlenk flask 4- iodoaniline (4.2 g, 20 mmol), trimethylsilylacetylene (3.5 ml, 2.4 g, 25 mmol), Pd(PPh 3 ) 4 (1.184 g, 1.025 mmol) and CuI (0.239 g, 1.256 mmol) were dissolved in anhydrous degassed NEt 3 (100 ml). The resulting solution was heated at reflux temperature overnight. Upon completion of the reaction, the black mixture was taken to dryness under reduced pressure and the residue was purified by silica gel column chromatography (hexane:ch 2 Cl 2 ) (1:1). Removal of solvent from the main fraction yielded a colourless oil that crystallized on standing. Yield 2.2 g, 12 mmol, 60%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.27 (d, J = 9 Hz, 2H, e), 6.57 (d, J = 9 Hz, 2H, f), 3.79 (s br., 2H, h), 0.22 (s, 9H, a). 5

Preparation of 4-ethynylaniline. 6 To a solution of 4-(trimethylsilylethynyl) aniline (2.12 g, 11.2 mmol) in THF (50 ml), TBAF (1M in THF, 12 ml ~12 mmol) was added and the resulting black solution stirred at room temperature overnight. The solution was then taken to dryness under reduced pressure and the remaining black oil was re-dissolved in CH 2 Cl 2 (50 ml). The organic phase was washed with water (2 50 ml), brine (1 50 ml) and dried over MgSO 4. Removal of solvent of the organic phase yielded the pure product as a light-brown solid. Yield 1.3 g, 11.1 mmol, 99%. 1 H NMR (400 MHz, CDCl 3 ) δ 7.29 (d, J = 9 Hz, 2H, e), 6.59 (d, J = 9 Hz, 2H, f), 3.82 (s, 2H, h), 2.95 (s, 1H, a). IR (nujol) cm -1 : 3485, 3388 (m) ν(nh 2 ); 3259 (m) ν(c C-H); 2097 (w) ν(c C). 6

NMR DATA (2d) trans-rucl(c CC 6 H 4 CO 2 Me-4)(dppe) 2 : 7

(2e) trans-rucl(c CC 6 H 4 NO 2-4)(dppe) 2 : 8

(2f) trans-rucl(c CC 6 H 4 C CSiMe 3-4)(dppe) 2 : 9

(2g) trans-rucl(c CC 6 H 4 C CCMe 3-4)(dppe) 2 : 10

(2i) trans-rucl(c CC 6 H 4 C CH-4)(dppe) 2 : 11

(3a) trans-ru(c CC 6 H 4 Me-4) 2 (dppe) 2 : 12

(3b) trans-ru(c CC 6 H 4 C 5 H 11-4) 2 (dppe) 2 : 13

(3c) trans-ru(c CC 6 H 4 OMe-4) 2 (dppe) 2 : 14

(3d) trans-ru(c CC 6 H 4 CO 2 Me-4) 2 (dppe) 2 : 15

(3e) trans-ru(c CC 6 H 4 NO 2-4) 2 (dppe) 2 : 16

(3f) trans-ru(c CC 6 H 4 C CSiMe 3-4) 2 (dppe) 2 : 17

(3g) trans-ru(c CC 6 H 4 C CCMe 3-4) 2 (dppe) 2 : 18

(3h) trans-ru(c CC 6 H 4 NH 2-4) 2 (dppe) 2 : 19

(3i) trans-ru(c CC 6 H 4 C CH-4) 2 (dppe) 2 : 20

(4) trans-ru(c CC 6 H 4 C CSiMe 3-4)(C CC 6 H 4 NH 2-4)(dppe) 2 : 21

22

(5) trans-ru(c CC 6 H 4 CO 2 Me-4)(C CC 6 H 4 NH 2-4)(dppe) 2 : 23

24

(6) trans-ru(c CC 6 H 4 CO 2 Me-4)(C CC 6 H 4 OMe-4)(dppe) 2 : 25

26

CRYSTALOGRAPHIC DATA Table S1. Crsytal and refinement data for trans-rucl(c CC 6 H 4 C CSiMe 3-4)(dppe) 2 (2f) Empirical formula C 65 H 61 ClP 4 RuSi x 1.5 CH 2 Cl 2 Formula weight 1258.02 Temperature / K 120 Crystal system triclinic Space group P-1 a / Å, b / Å, c / Å 13.4989(4), 14.8937(4), 17.8696(5) /, β/, γ/ 113.418(10), 98.650(10), 103.321(10) Volume / Å 3 3088.00(15) Z 2 ρ calc / mg mm -3 1.353 µ / mm -1 0.590 F(000) 1298 Crystal size / mm 3 0.32 0.15 0.1 2Θ range for data collection 2.58 to 57 Index ranges -18 h 18, -19 k 19, -23 l 23 Reflections collected 37101 Independent reflections 15588[R(int) = 0.1044] Data/restraints/parameters 15588/1/699 Goodness-of-fit on F 2 1.012 Final R indexes [I>2σ (I)] R 1 = 0.0627, wr 2 = 0.1570 Final R indexes [all data] R 1 = 0.1132, wr 2 = 0.1780 Largest diff. peak/hole / e Å -3 1.894/-0.975 Figure S1. A plot of a molecule of 2f showing the atom labelling scheme. 27

Table S2. Crystallographically determined bond lengths for 2f. Atom Atom Length/Å Atom Atom Length/Å Ru1 Cl1 2.5041(11) C34 C35 1.381(7) Ru1 P1 2.3576(11) C35 C36 1.400(6) Ru1 P2 2.3739(11) C41 C42 1.399(6) Ru1 P3 2.3725(11) C41 C46 1.397(6) Ru1 P4 2.3336(12) C42 C43 1.382(7) Ru1 C1 2.005(5) C43 C44 1.375(7) P1 C11 1.839(4) C44 C45 1.372(7) P1 C21 1.842(4) C45 C46 1.380(6) P1 C31 1.834(4) C51 C52 1.385(6) P2 C12 1.863(4) C51 C56 1.391(6) P2 C41 1.841(5) C52 C53 1.383(6) P2 C51 1.844(4) C53 C54 1.400(7) P3 C13 1.860(4) C54 C55 1.373(7) P3 C61 1.846(4) C55 C56 1.385(6) P3 C71 1.835(4) C61 C62 1.405(6) P4 C14 1.848(4) C61 C66 1.388(6) P4 C81 1.839(4) C62 C63 1.399(6) P4 C91 1.818(5) C63 C64 1.380(7) Si C10 1.845(5) C64 C65 1.379(7) Si C15 1.868(6) C65 C66 1.392(6) Si C16 1.859(5) C71 C72 1.402(6) Si C17 1.862(5) C71 C76 1.392(6) C1 C2 1.196(6) C72 C73 1.376(6) C2 C3 1.434(6) C73 C74 1.376(7) C3 C4 1.392(6) C74 C75 1.384(7) C3 C8 1.401(6) C75 C76 1.389(6) C4 C5 1.389(6) C81 C82 1.383(6) C5 C6 1.401(7) C81 C86 1.385(6) C6 C7 1.385(7) C82 C83 1.388(6) C6 C9 1.444(7) C83 C84 1.370(7) C7 C8 1.387(7) C84 C85 1.386(7) C9 C10 1.186(7) C85 C86 1.396(6) C11 C12 1.526(6) C91 C92 1.383(6) C13 C14 1.536(6) C91 C96 1.401(6) C21 C22 1.405(6) C92 C93 1.392(7) C21 C26 1.400(6) C93 C94 1.375(7) C22 C23 1.375(6) C94 C95 1.392(7) C23 C24 1.397(7) C95 C96 1.368(6) C24 C25 1.362(7) Cl0A C2SA 1.716(9) C25 C26 1.384(6) Cl4 C2SA 1.769(9) C31 C32 1.391(6) Cl1A C2SA 1.722(8) C31 C36 1.388(6) Cl5 C2SA 1.777(11) C32 C33 1.392(7) Cl2 C1S 1.769(5) C33 C34 1.381(7) Cl3 C1S 1.755(5) 28

Table S3. Crystallographically determined bond angles for 2f. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 Ru1 Cl1 103.68(4) C22 C23 C24 120.6(5) P1 Ru1 P2 82.38(4) C25 C24 C23 119.8(5) P1 Ru1 P3 176.06(4) C24 C25 C26 120.4(5) P2 Ru1 Cl1 89.25(4) C25 C26 C21 121.0(5) P3 Ru1 Cl1 79.46(4) C32 C31 P1 121.3(4) P3 Ru1 P2 100.14(4) C36 C31 P1 119.6(3) P4 Ru1 Cl1 87.17(4) C36 C31 C32 118.9(4) P4 Ru1 P1 97.42(4) C31 C32 C33 120.7(5) P4 Ru1 P2 176.26(4) C34 C33 C32 119.9(5) P4 Ru1 P3 80.26(4) C33 C34 C35 120.1(5) C1 Ru1 Cl1 175.62(12) C34 C35 C36 120.0(5) C1 Ru1 P1 79.41(12) C31 C36 C35 120.3(4) C1 Ru1 P2 88.09(12) C42 C41 P2 121.4(4) C1 Ru1 P3 97.59(12) C46 C41 P2 120.5(3) C1 Ru1 P4 95.55(12) C46 C41 C42 118.1(4) C11 P1 Ru1 105.85(14) C43 C42 C41 120.4(5) C11 P1 C21 102.3(2) C44 C43 C42 120.1(5) C21 P1 Ru1 120.24(14) C45 C44 C43 120.7(5) C31 P1 Ru1 123.24(15) C44 C45 C46 119.6(5) C31 P1 C11 99.9(2) C45 C46 C41 121.1(5) C31 P1 C21 101.7(2) C52 C51 P2 121.5(3) C12 P2 Ru1 108.22(14) C52 C51 C56 119.2(4) C41 P2 Ru1 120.19(14) C56 C51 P2 119.3(3) C41 P2 C12 101.4(2) C53 C52 C51 120.8(4) C41 P2 C51 101.0(2) C52 C53 C54 119.3(4) C51 P2 Ru1 121.11(15) C55 C54 C53 120.0(4) C51 P2 C12 101.88(19) C54 C55 C56 120.3(5) C13 P3 Ru1 107.37(14) C55 C56 C51 120.3(4) C61 P3 Ru1 123.17(14) C62 C61 P3 117.7(3) C61 P3 C13 98.6(2) C66 C61 P3 122.9(3) C71 P3 Ru1 120.45(14) C66 C61 C62 119.1(4) C71 P3 C13 104.16(19) C63 C62 C61 120.0(4) C71 P3 C61 99.7(2) C64 C63 C62 120.1(4) C14 P4 Ru1 106.55(14) C65 C64 C63 119.8(4) C81 P4 Ru1 120.48(15) C64 C65 C66 120.8(5) C81 P4 C14 98.9(2) C61 C66 C65 120.1(4) C91 P4 Ru1 118.94(14) C72 C71 P3 118.5(3) C91 P4 C14 106.6(2) C76 C71 P3 123.0(3) C91 P4 C81 102.9(2) C76 C71 C72 118.4(4) C10 Si C15 108.0(3) C73 C72 C71 120.9(4) C10 Si C16 107.6(2) C72 C73 C74 120.1(5) C10 Si C17 108.6(2) C73 C74 C75 120.1(4) C16 Si C15 110.8(3) C74 C75 C76 120.1(5) C16 Si C17 110.9(3) C75 C76 C71 120.3(4) C17 Si C15 110.8(3) C82 C81 P4 123.4(4) 29

C2 C1 Ru1 175.2(4) C82 C81 C86 118.9(4) C1 C2 C3 174.1(5) C86 C81 P4 117.7(3) C4 C3 C2 120.9(4) C81 C82 C83 121.1(5) C4 C3 C8 116.7(4) C84 C83 C82 119.7(5) C8 C3 C2 122.4(4) C83 C84 C85 120.4(5) C5 C4 C3 122.4(4) C84 C85 C86 119.7(5) C4 C5 C6 119.8(4) C81 C86 C85 120.3(5) C5 C6 C9 119.4(4) C92 C91 P4 123.1(4) C7 C6 C5 118.6(4) C92 C91 C96 118.3(4) C7 C6 C9 122.0(5) C96 C91 P4 118.6(4) C6 C7 C8 120.8(5) C91 C92 C93 120.7(5) C7 C8 C3 121.6(5) C94 C93 C92 120.3(5) C10 C9 C6 178.2(6) C93 C94 C95 119.3(5) C9 C10 Si 180.0(7) C96 C95 C94 120.4(5) C12 C11 P1 106.6(3) C95 C96 C91 120.9(4) C11 C12 P2 110.0(3) Cl0A C2SA Cl4 123.6(6) C14 C13 P3 113.3(3) Cl0A C2SA Cl1A 109.1(6) C13 C14 P4 114.1(3) Cl0A C2SA Cl5 10.1(4) C22 C21 P1 120.5(4) Cl4 C2SA Cl5 113.6(5) C26 C21 P1 121.4(3) Cl1A C2SA Cl4 14.7(3) C26 C21 C22 118.1(4) Cl1A C2SA Cl5 99.1(5) C23 C22 C21 120.1(5) Cl3 C1S Cl2 111.9(3) Table S4. Crystal and refinement data for trans-rucl(c CC 6 H 4 CMe 3-4)(dppe) 2 (2g) Empirical formula C 66 H 61 ClP 4 Ru Formula weight 1114.55 Temperature/K 120 Crystal system triclinic Space group P1 a/å 9.2573(4) b/å 12.9014(6) c/å 13.6270(7) / 63.7590(10) β/ 71.2670(10) γ/ 80.4290(10) Volume/Å 3 1381.88(11) Z 1 ρ calc mg/mm 3 1.339 m/mm -1 0.489 F(000) 578 Crystal size/mm 3 0.34 0.2 0.16 2Θ range for data collection 3.48 to 60 30

Index ranges -13 h 13, -18 k 18, -19 l 19 Reflections collected 18235 Independent reflections 15422[R(int) = 0.0195] Data/restraints/parameters 15422/3/641 Goodness-of-fit on F 2 1.081 Final R indexes [I>=2σ (I)] R 1 = 0.0412, wr 2 = 0.1060 Final R indexes [all data] R 1 = 0.0478, wr 2 = 0.1099 Largest diff. peak/hole / e Å -3 0.991/-1.018 Flack Parameter 0.0(3) 31

Figure S2. Plot of a molecule of 2g showing the atom labelling scheme Table S5. Crystallographically determined bond lengths for 2g. Atom Atom Length/Å Atom Atom Length/Å Ru1 Cl1 2.4799(11) C31 C36 1.384(6) Ru1 Cl1A 2.437(15) C32 C33 1.383(6) Ru1 P1 2.3629(10) C33 C34 1.374(7) Ru1 P2 2.3888(10) C34 C35 1.382(7) Ru1 P3 2.3565(10) C35 C36 1.407(6) Ru1 P4 2.3696(10) C41 C42 1.383(6) Ru1 C1 1.997(4) C41 C46 1.397(6) P1 C15 1.867(4) C42 C43 1.417(6) P1 C21 1.835(4) C43 C44 1.377(8) P1 C31 1.843(4) C44 C45 1.404(7) P2 C16 1.850(4) C45 C46 1.397(6) P2 C41 1.841(4) C51 C52 1.409(6) P2 C51 1.851(4) C51 C56 1.392(5) P3 C17 1.857(4) C52 C53 1.393(6) P3 C61 1.842(4) C53 C54 1.380(7) P3 C71 1.845(4) C54 C55 1.377(7) P4 C18 1.844(4) C55 C56 1.406(6) P4 C81 1.825(4) C61 C62 1.388(6) P4 C91 1.843(4) C61 C66 1.396(6) C1 C2 1.234(5) C62 C63 1.386(6) C2 C3 1.416(5) C63 C64 1.391(7) C3 C4 1.420(5) C64 C65 1.388(7) C3 C8 1.403(4) C65 C66 1.400(6) C4 C5 1.392(4) C71 C72 1.389(6) C5 C6 1.374(5) C71 C76 1.387(6) 32

C6 C7 1.401(5) C72 C73 1.387(6) C6 C9 1.452(5) C73 C74 1.382(7) C7 C8 1.401(4) C74 C75 1.370(6) C9 C10 1.192(5) C75 C76 1.398(6) C10 C11 1.479(5) C81 C82 1.409(6) C11 C12 1.504(5) C81 C86 1.409(6) C11 C13 1.536(5) C82 C83 1.364(6) C11 C14 1.528(5) C83 C84 1.395(7) C15 C16 1.532(5) C84 C85 1.368(7) C17 C18 1.523(5) C85 C86 1.387(6) C21 C22 1.396(6) C91 C92 1.387(6) C21 C26 1.398(6) C91 C96 1.419(6) C22 C23 1.381(6) C92 C93 1.396(6) C23 C24 1.387(7) C93 C94 1.397(6) C24 C25 1.370(6) C94 C95 1.377(6) C25 C26 1.392(6) C95 C96 1.389(6) C31 C32 1.407(6) Table S6. Crystallographically determined bond angles for 2g. Atom Atom Atom Angle/ Atom Atom Atom Angle/ Cl1A Ru1 Cl1 179.6(4) C18 C17 P3 112.4(3) P1 Ru1 Cl1 90.11(4) C17 C18 P4 107.4(3) P1 Ru1 Cl1A 89.5(4) C22 C21 P1 120.3(3) P1 Ru1 P2 81.95(4) C22 C21 C26 118.0(4) P1 Ru1 P4 97.82(3) C26 C21 P1 121.5(3) P2 Ru1 Cl1 80.71(4) C23 C22 C21 121.0(4) P2 Ru1 Cl1A 99.1(4) C22 C23 C24 120.5(4) P3 Ru1 Cl1 89.76(4) C25 C24 C23 119.2(4) P3 Ru1 Cl1A 90.6(4) C24 C25 C26 121.1(4) P3 Ru1 P1 179.41(5) C25 C26 C21 120.2(4) P3 Ru1 P2 98.60(3) C32 C31 P1 121.0(3) P3 Ru1 P4 81.63(4) C36 C31 P1 120.1(3) P4 Ru1 Cl1 100.18(4) C36 C31 C32 118.8(4) P4 Ru1 Cl1A 80.0(4) C33 C32 C31 119.7(4) P4 Ru1 P2 179.09(4) C34 C33 C32 121.8(5) C1 Ru1 Cl1 177.96(13) C33 C34 C35 119.1(4) C1 Ru1 Cl1A 2.2(5) C34 C35 C36 120.3(4) C1 Ru1 P1 90.86(13) C31 C36 C35 120.4(4) C1 Ru1 P2 97.66(13) C42 C41 P2 120.4(3) C1 Ru1 P3 89.28(13) C42 C41 C46 119.8(4) C1 Ru1 P4 81.46(13) C46 C41 P2 119.7(3) C15 P1 Ru1 109.52(13) C41 C42 C43 120.0(4) C21 P1 Ru1 119.52(13) C44 C43 C42 120.4(5) C21 P1 C15 101.36(18) C43 C44 C45 119.5(4) C21 P1 C31 102.61(19) C46 C45 C44 120.2(5) 33

C31 P1 Ru1 118.89(14) C45 C46 C41 120.2(4) C31 P1 C15 102.35(18) C52 C51 P2 119.2(3) C16 P2 Ru1 104.08(14) C56 C51 P2 121.9(3) C16 P2 C51 99.35(19) C56 C51 C52 118.9(4) C41 P2 Ru1 120.65(14) C53 C52 C51 119.8(4) C41 P2 C16 104.08(19) C54 C53 C52 120.8(4) C41 P2 C51 99.89(19) C55 C54 C53 120.1(4) C51 P2 Ru1 125.18(13) C54 C55 C56 120.0(4) C17 P3 Ru1 108.91(13) C51 C56 C55 120.4(4) C61 P3 Ru1 119.63(13) C62 C61 P3 120.2(3) C61 P3 C17 101.89(17) C62 C61 C66 118.6(4) C61 P3 C71 102.70(18) C66 C61 P3 121.1(3) C71 P3 Ru1 118.92(13) C63 C62 C61 121.4(4) C71 P3 C17 102.25(18) C62 C63 C64 119.7(4) C18 P4 Ru1 104.31(13) C65 C64 C63 120.0(4) C81 P4 Ru1 120.60(13) C64 C65 C66 119.8(5) C81 P4 C18 103.41(18) C61 C66 C65 120.5(4) C81 P4 C91 99.83(19) C72 C71 P3 121.7(3) C91 P4 Ru1 125.11(13) C76 C71 P3 120.2(3) C91 P4 C18 99.95(19) C76 C71 C72 117.9(4) C2 C1 Ru1 177.1(4) C73 C72 C71 121.6(4) C1 C2 C3 175.8(4) C74 C73 C72 119.7(4) C2 C3 C4 120.7(3) C75 C74 C73 119.8(4) C8 C3 C2 122.2(3) C74 C75 C76 120.4(4) C8 C3 C4 117.1(3) C71 C76 C75 120.7(4) C5 C4 C3 120.9(3) C82 C81 P4 121.6(3) C6 C5 C4 121.3(3) C86 C81 P4 121.3(3) C5 C6 C7 119.2(3) C86 C81 C82 117.1(4) C5 C6 C9 118.9(3) C83 C82 C81 120.6(4) C7 C6 C9 122.0(3) C82 C83 C84 121.6(5) C6 C7 C8 120.2(3) C85 C84 C83 119.1(4) C7 C8 C3 121.3(3) C84 C85 C86 120.3(5) C10 C9 C6 177.8(5) C85 C86 C81 121.4(4) C9 C10 C11 175.1(4) C92 C91 P4 123.1(3) C10 C11 C12 108.1(3) C92 C91 C96 118.0(4) C10 C11 C13 112.1(3) C96 C91 P4 118.8(3) C10 C11 C14 108.4(3) C91 C92 C93 121.4(4) C12 C11 C13 109.9(3) C92 C93 C94 119.3(4) C12 C11 C14 110.8(3) C95 C94 C93 120.5(4) C14 C11 C13 107.5(3) C94 C95 C96 120.0(4) C16 C15 P1 110.8(3) C95 C96 C91 120.7(4) C15 C16 P2 107.9(3) 34

Table S7. Crystal and refinement details for trans-rucl(c CC 6 H 4 C CH-4)(dppe) 2 (2i) Empirical formula C 62 H 53 ClP 4 Ru Formula weight 1058.44 Temperature/K 120 Wavelength/Å 0.6889 Crystal system monoclinic Space group P2 1 /c a/å 11.5037(7) b/å 22.4968(8) c/å 19.4374(10) / 90.00 β/ 94.037(6) γ/ 90.00 Volume/Å 3 5017.9(4) Z 4 ρ calc mg/mm 3 1.401 m/mm -1 0.534 F(000) 2184.0 Crystal size/mm 3 0.08 0.08 0.001 2Θ range for data collection 2.68 to 57 Index ranges -15 h 15, -31 k 31, -26 l 25 Reflections collected 53556 Independent reflections 13451[R(int) = 0.0386] Data/restraints/parameters 13451/0/613 Goodness-of-fit on F 2 1.091 Final R indexes [I>=2σ (I)] R 1 = 0.0376, wr 2 = 0.0936 Final R indexes [all data] R 1 = 0.0470, wr 2 = 0.0987 Largest diff. peak/hole / e Å -3 0.46/-0.62 35

Figure S3. A plot of a molecule of 2i showing the atom labelling scheme. Table S8. Crystallographically determined bond lengths for 2i. Atom Atom Length/Å Atom Atom Length/Å Ru1 Cl1 2.5030(6) C33 C34 1.390(4) Ru1 P1 2.3837(6) C34 C35 1.389(4) Ru1 P2 2.3751(5) C35 C36 1.401(3) Ru1 P3 2.3869(6) C41 C42 1.401(3) Ru1 P4 2.4058(6) C41 C46 1.413(3) Ru1 C1 2.027(2) C42 C43 1.398(3) P1 C11 1.850(2) C43 C44 1.389(4) P1 C21 1.852(2) C44 C45 1.390(4) P1 C31 1.849(2) C45 C46 1.401(3) P2 C12 1.864(2) C51 C52 1.406(3) P2 C41 1.845(2) C51 C56 1.412(3) P2 C51 1.853(2) C52 C53 1.404(3) P3 C13 1.861(2) C53 C54 1.398(3) P3 C61 1.851(2) C54 C55 1.395(4) P3 C71 1.851(2) C55 C56 1.403(3) P4 C14 1.881(2) C61 C62 1.403(3) P4 C81 1.863(2) C61 C66 1.418(3) P4 C91 1.845(2) C62 C63 1.405(3) C1 C2 1.190(3) C63 C64 1.392(4) C2 C3 1.456(3) C64 C65 1.394(4) C3 C4 1.416(3) C65 C66 1.387(4) C3 C8 1.414(3) C71 C72 1.409(3) C4 C5 1.392(3) C71 C76 1.399(3) C5 C6 1.403(3) C72 C73 1.401(3) C6 C7 1.402(3) C73 C74 1.392(4) 36

C6 C9 1.441(3) C74 C75 1.385(4) C7 C8 1.393(3) C75 C76 1.402(3) C9 C10 1.195(4) C81 C82 1.416(3) C11 C12 1.540(3) C81 C86 1.402(3) C13 C14 1.537(3) C82 C83 1.397(3) C21 C22 1.399(3) C83 C84 1.397(4) C21 C26 1.404(3) C84 C85 1.397(4) C22 C23 1.409(3) C85 C86 1.405(3) C23 C24 1.389(4) C91 C92 1.410(3) C24 C25 1.382(4) C91 C96 1.402(3) C25 C26 1.399(3) C92 C93 1.405(3) C31 C32 1.404(3) C93 C94 1.387(4) C31 C36 1.399(3) C94 C95 1.387(4) C32 C33 1.400(3) C95 C96 1.412(4) Table S9. Crystallographically determined bond angles for 2i. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 Ru1 Cl1 90.332(19) C24 C23 C22 119.9(2) P1 Ru1 P3 174.228(19) C25 C24 C23 120.0(2) P1 Ru1 P4 100.792(19) C24 C25 C26 120.5(2) P2 Ru1 Cl1 92.608(19) C25 C26 C21 120.6(2) P2 Ru1 P1 83.302(19) C32 C31 P1 120.15(17) P2 Ru1 P3 94.501(19) C36 C31 P1 121.09(16) P2 Ru1 P4 175.904(19) C36 C31 C32 118.7(2) P3 Ru1 Cl1 84.425(19) C33 C32 C31 120.4(2) P3 Ru1 P4 81.436(19) C34 C33 C32 120.6(2) P4 Ru1 Cl1 87.53(2) C35 C34 C33 119.3(2) C1 Ru1 Cl1 172.95(6) C34 C35 C36 120.6(2) C1 Ru1 P1 83.03(6) C31 C36 C35 120.5(2) C1 Ru1 P2 84.29(6) C42 C41 P2 122.29(17) C1 Ru1 P3 102.10(6) C42 C41 C46 118.5(2) C1 Ru1 P4 96.02(6) C46 C41 P2 119.21(16) C11 P1 Ru1 105.65(7) C43 C42 C41 120.9(2) C11 P1 C21 103.22(10) C44 C43 C42 120.0(2) C21 P1 Ru1 118.46(7) C43 C44 C45 120.1(2) C31 P1 Ru1 124.72(7) C44 C45 C46 120.3(2) C31 P1 C11 100.63(9) C45 C46 C41 120.2(2) C31 P1 C21 100.98(9) C52 C51 P2 120.48(16) C12 P2 Ru1 108.90(7) C52 C51 C56 118.56(19) C41 P2 Ru1 121.82(7) C56 C51 P2 120.90(16) C41 P2 C12 100.87(10) C53 C52 C51 120.9(2) C41 P2 C51 101.41(9) C54 C53 C52 119.9(2) 37

C51 P2 Ru1 117.86(7) C55 C54 C53 119.8(2) C51 P2 C12 103.35(9) C54 C55 C56 120.5(2) C13 P3 Ru1 104.85(7) C55 C56 C51 120.3(2) C61 P3 Ru1 123.21(7) C62 C61 P3 121.30(17) C61 P3 C13 98.85(10) C62 C61 C66 118.1(2) C61 P3 C71 101.49(10) C66 C61 P3 120.42(16) C71 P3 Ru1 121.99(7) C61 C62 C63 120.5(2) C71 P3 C13 102.21(10) C64 C63 C62 120.2(2) C14 P4 Ru1 108.28(7) C63 C64 C65 120.0(2) C81 P4 Ru1 127.13(7) C66 C65 C64 120.1(2) C81 P4 C14 96.90(10) C65 C66 C61 121.1(2) C91 P4 Ru1 116.76(7) C72 C71 P3 122.03(17) C91 P4 C14 104.03(10) C76 C71 P3 119.46(17) C91 P4 C81 100.13(10) C76 C71 C72 118.5(2) C2 C1 Ru1 172.2(2) C73 C72 C71 120.2(2) C1 C2 C3 179.0(2) C74 C73 C72 120.6(2) C4 C3 C2 121.3(2) C75 C74 C73 119.6(2) C8 C3 C2 120.68(19) C74 C75 C76 120.4(2) C8 C3 C4 118.0(2) C71 C76 C75 120.7(2) C5 C4 C3 120.8(2) C82 C81 P4 118.34(17) C4 C5 C6 120.8(2) C86 C81 P4 123.15(17) C5 C6 C9 121.6(2) C86 C81 C82 118.3(2) C7 C6 C5 118.9(2) C83 C82 C81 120.9(2) C7 C6 C9 119.5(2) C84 C83 C82 120.2(2) C8 C7 C6 120.7(2) C83 C84 C85 119.6(2) C7 C8 C3 120.8(2) C84 C85 C86 120.3(2) C10 C9 C6 176.8(3) C81 C86 C85 120.7(2) C12 C11 P1 109.12(14) C92 C91 P4 119.04(17) C11 C12 P2 110.45(15) C96 C91 P4 122.34(18) C14 C13 P3 107.77(14) C96 C91 C92 118.4(2) C13 C14 P4 113.09(15) C93 C92 C91 121.0(2) C22 C21 P1 124.09(16) C94 C93 C92 119.9(3) C22 C21 C26 118.4(2) C95 C94 C93 119.9(2) C26 C21 P1 117.51(17) C94 C95 C96 120.9(3) C21 C22 C23 120.7(2) C91 C96 C95 119.9(2) 38

Table S10. Crystal and refinement data for trans-ru(c CC 6 H 4 Me-4) 2 (dppe) 2 (3a) Empirical formula C 70 H 62 P 4 Ru Formula weight 1128.15 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.4458(4) b/å 12.9907(6) c/å 13.5890(6) / 117.3140(10) β/ 94.8710(10) γ/ 104.7240(10) Volume/Å 3 1392.94(11) Z 1 ρ calc mg/mm 3 1.345 m/mm -1 0.440 F(000) 586 Crystal size/mm 3 0.52 0.1 0.04 Theta range for data collection 3.48 to 59 Index ranges -13 h 13, -17 k 17, -18 l 18 Reflections collected 16041 Independent reflections 7679[R(int) = 0.0321] Data/restraints/parameters 7679/0/341 Goodness-of-fit on F 2 1.056 Final R indexes [I>2σ (I)] R 1 = 0.0397, wr 2 = 0.1004 Final R indexes [all data] R 1 = 0.0515, wr 2 = 0.1078 Largest diff. peak/hole / e Å -3 1.117/-1.580 39

Figure S4. A plot of a molecule of 3a showing the atom labelling scheme. Table S11. Crystallographically determined bond lengths for 3a. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3485(5) C21 C26 1.398(3) Ru1 P1 1 2.3485(5) C22 C23 1.395(3) Ru1 P2 2.3495(5) C23 C24 1.386(3) Ru1 P2 1 2.3495(5) C24 C25 1.388(3) Ru1 C1 2.065(2) C25 C26 1.384(3) Ru1 C1 1 2.065(2) C31 C32 1.397(3) P1 C10 1.848(2) C31 C36 1.397(3) P1 C21 1.848(2) C32 C33 1.389(3) P1 C31 1.833(2) C33 C34 1.386(3) P2 C11 1.857(2) C34 C35 1.390(3) P2 C41 1.837(2) C35 C36 1.386(3) P2 C51 1.838(2) C41 C42 1.390(3) C1 C2 1.210(3) C41 C46 1.396(3) C2 C3 1.440(3) C42 C43 1.394(3) C3 C4 1.398(3) C43 C44 1.385(3) C3 C8 1.398(3) C44 C45 1.386(3) C4 C5 1.390(3) C45 C46 1.387(3) C5 C6 1.386(3) C51 C52 1.399(3) C6 C7 1.379(3) C51 C56 1.389(3) C6 C9 1.516(3) C52 C53 1.394(3) C7 C8 1.392(3) C53 C54 1.390(3) C10 C11 1.525(3) C54 C55 1.388(3) C21 C22 1.397(3) C55 C56 1.397(3) 40

Table S12. Crystallographically determined bond angles for 3a. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 180.00(2) C6 C7 C8 121.7(2) P1 1 Ru1 P2 97.014(18) C7 C8 C3 120.5(2) P1 Ru1 P2 82.985(17) C11 C10 P1 106.41(13) P1 1 Ru1 P2 1 82.986(18) C10 C11 P2 110.34(13) P1 Ru1 P2 1 97.015(18) C22 C21 P1 122.22(15) P2 Ru1 P2 1 180.0 C22 C21 C26 118.49(18) C1 1 Ru1 P1 1 99.23(6) C26 C21 P1 119.23(15) C1 Ru1 P1 1 80.77(6) C23 C22 C21 120.4(2) C1 Ru1 P1 99.23(6) C24 C23 C22 120.4(2) C1 1 Ru1 P1 80.77(6) C23 C24 C25 119.5(2) C1 1 Ru1 P2 87.21(5) C26 C25 C24 120.3(2) C1 Ru1 P2 92.79(5) C25 C26 C21 120.9(2) C1 1 Ru1 P2 1 92.79(5) C32 C31 P1 120.28(16) C1 Ru1 P2 1 87.21(5) C36 C31 P1 121.31(15) C1 Ru1 C1 1 180.0 C36 C31 C32 118.40(19) C10 P1 Ru1 105.15(7) C33 C32 C31 120.8(2) C10 P1 C21 98.50(9) C34 C33 C32 120.2(2) C21 P1 Ru1 125.25(7) C33 C34 C35 119.6(2) C31 P1 Ru1 120.00(6) C36 C35 C34 120.2(2) C31 P1 C10 104.85(9) C35 C36 C31 120.8(2) C31 P1 C21 99.65(9) C42 C41 P2 122.77(16) C11 P2 Ru1 108.30(7) C42 C41 C46 118.39(19) C41 P2 Ru1 120.51(7) C46 C41 P2 118.81(16) C41 P2 C11 101.40(9) C41 C42 C43 120.7(2) C41 P2 C51 101.40(9) C44 C43 C42 120.3(2) C51 P2 Ru1 119.96(7) C43 C44 C45 119.3(2) C51 P2 C11 102.46(9) C44 C45 C46 120.4(2) C2 C1 Ru1 174.54(17) C45 C46 C41 120.8(2) C1 C2 C3 175.6(2) C52 C51 P2 120.70(15) C4 C3 C2 121.04(19) C56 C51 P2 120.40(15) C8 C3 C2 121.3(2) C56 C51 C52 118.88(18) C8 C3 C4 117.65(19) C53 C52 C51 120.4(2) C5 C4 C3 120.9(2) C54 C53 C52 120.1(2) C6 C5 C4 121.2(2) C55 C54 C53 119.97(19) C5 C6 C9 120.7(2) C54 C55 C56 119.8(2) C7 C6 C5 118.0(2) C51 C56 C55 120.88(19) C7 C6 C9 121.3(2) 41

Table S13. Crystal and refinement data for trans-ru(c CC 6 H 4 C 5 H 11-4) 2 (dppe) 2 (3b) Empirical formula C 78 H 78 P 4 Ru x 2 CHCl 3 Formula weight 1479.09 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.6718(2) b/å 13.2334(3) c/å 15.1804(4) / 78.104(10) β/ 76.997(10) γ/ 72.329(10) Volume/Å 3 1783.81(7) Z 1 ρ calc mg/mm 3 1.377 m/mm -1 0.578 F(000) 766 Crystal size/mm 3 0.17 0.12 0.06 2Θ range for data collection 3.26 to 60 Index ranges -13 h 13, -18 k 18, -21 l 21 Reflections collected 31919 Independent reflections 10417[R(int) = 0.0498] Data/restraints/parameters 10417/0/572 Goodness-of-fit on F 2 0.932 Final R indexes [I>=2σ (I)] R 1 = 0.0330, wr 2 = 0.0699 Final R indexes [all data] R 1 = 0.0500, wr 2 = 0.0750 Largest diff. peak/hole / e Å -3 0.686/-0.658 42

Figure S5. A plot of a molecule of 3b showing the atom labelling scheme. Table S14. Crystallographically determined bond lengths for 3b. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 1 2.3576(5) C21 C26 1.405(2) Ru1 P1 2.3576(5) C22 C23 1.393(2) Ru1 P2 1 2.3526(5) C23 C24 1.384(3) Ru1 P2 2.3525(5) C24 C25 1.385(3) Ru1 C1 1 2.0666(16) C25 C26 1.386(2) Ru1 C1 2.0666(16) C31 C32 1.397(2) P1 C14 1.8440(17) C31 C36 1.392(2) P1 C21 1.8493(17) C32 C33 1.389(2) P1 C31 1.8350(16) C33 C34 1.384(3) P2 C15 1.8570(17) C34 C35 1.381(3) P2 C41 1.8317(17) C35 C36 1.393(2) P2 C51 1.8349(16) C41 C42 1.397(2) C1 C2 1.206(2) C41 C46 1.392(2) C2 C3 1.441(2) C42 C43 1.389(2) C3 C4 1.405(2) C43 C44 1.381(3) C3 C8 1.406(2) C44 C45 1.383(3) C4 C5 1.388(2) C45 C46 1.393(2) C5 C6 1.387(3) C51 C52 1.388(2) C6 C7 1.397(3) C51 C56 1.401(2) C6 C9 1.508(3) C52 C53 1.393(2) C7 C8 1.382(2) C53 C54 1.384(3) C9 C10 1.515(3) C54 C55 1.385(3) C10 C11 1.529(3) C55 C56 1.385(2) C11 C12 1.525(3) Cl1 C1S 1.760(2) C12 C13 1.510(3) Cl2 C1S 1.758(2) C14 C15 1.525(2) Cl3 C1S 1.766(2) 43

C21 C22 1.393(2) Table S15. Crystallographically determined bond angles for 3b. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 Ru1 P1 1 180.0 C9 C10 C11 112.13(16) P2 Ru1 P1 82.801(16) C12 C11 C10 114.07(17) P2 1 Ru1 P1 97.199(16) C13 C12 C11 113.59(18) P2 1 Ru1 P1 1 82.801(16) C15 C14 P1 106.38(11) P2 Ru1 P1 1 97.198(16) C14 C15 P2 110.14(11) P2 Ru1 P2 1 180.0 C22 C21 P1 121.86(12) C1 1 Ru1 P1 1 80.29(4) C22 C21 C26 118.34(15) C1 Ru1 P1 1 99.71(4) C26 C21 P1 119.69(13) C1 1 Ru1 P1 99.71(4) C21 C22 C23 120.39(16) C1 Ru1 P1 80.29(4) C24 C23 C22 120.60(17) C1 Ru1 P2 87.48(4) C23 C24 C25 119.67(17) C1 1 Ru1 P2 92.52(4) C24 C25 C26 120.10(17) C1 1 Ru1 P2 1 87.48(4) C25 C26 C21 120.90(17) C1 Ru1 P2 1 92.51(4) C32 C31 P1 119.72(13) C1 1 Ru1 C1 180.0 C36 C31 P1 121.68(13) C14 P1 Ru1 105.11(6) C36 C31 C32 118.60(15) C14 P1 C21 98.25(8) C33 C32 C31 120.68(16) C21 P1 Ru1 124.80(5) C34 C33 C32 120.06(17) C31 P1 Ru1 120.99(5) C35 C34 C33 119.93(17) C31 P1 C14 104.51(8) C34 C35 C36 120.20(17) C31 P1 C21 99.49(7) C31 C36 C35 120.53(16) C15 P2 Ru1 108.30(6) C42 C41 P2 119.03(13) C41 P2 Ru1 119.44(5) C46 C41 P2 122.49(13) C41 P2 C15 102.32(8) C46 C41 C42 118.35(16) C41 P2 C51 101.89(7) C43 C42 C41 120.74(17) C51 P2 Ru1 120.48(6) C44 C43 C42 120.37(18) C51 P2 C15 101.68(8) C43 C44 C45 119.54(17) C2 C1 Ru1 174.38(14) C44 C45 C46 120.38(17) C1 C2 C3 174.63(17) C45 C46 C41 120.61(17) C4 C3 C2 120.85(16) C52 C51 P2 120.84(12) C8 C3 C2 121.45(15) C52 C51 C56 118.31(15) C8 C3 C4 117.59(16) C56 C51 P2 120.86(13) C5 C4 C3 120.71(17) C51 C52 C53 121.02(16) C6 C5 C4 121.71(17) C54 C53 C52 119.87(17) C5 C6 C7 117.54(16) C53 C54 C55 119.87(16) C5 C6 C9 121.29(18) C56 C55 C54 120.18(17) C7 C6 C9 121.15(18) C55 C56 C51 120.76(16) C8 C7 C6 121.76(17) Cl1 C1S Cl3 109.73(11) C7 C8 C3 120.66(16) Cl2 C1S Cl1 110.68(11) C6 C9 C10 115.36(16) Cl2 C1S Cl3 109.79(12) 44

Table S16. Crystal and refinement data for trans-ru(c CC 6 H 4 OMe-4) 2 (dppe) 2 (3c) Empirical formula C 70 H 62 O 2 P 4 Ru x C 7 H 7 Formula weight 1251.27 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.1943(4) b/å 12.7621(5) c/å 13.5658(6) / 76.5760(10) β/ 89.8530(10) γ/ 80.9940(10) Volume/Å 3 1528.27(11) Z 1 ρ calc mg/mm 3 1.360 m/mm -1 0.411 F(000) 651 Crystal size/mm 3 0.46 0.18 0.1 2Θ range for data collection 3.08 to 60 Index ranges -12 h 12, -17 k 17, -19 l 18 Reflections collected 20100 Independent reflections 8842[R(int) = 0.0243] Data/restraints/parameters 8842/0/518 Goodness-of-fit on F 2 1.052 Final R indexes [I>=2σ (I)] R 1 = 0.0348, wr 2 = 0.0886 Final R indexes [all data] R 1 = 0.0414, wr 2 = 0.0934 Largest diff. peak/hole / e Å -3 0.980/-0.840 45

Figure S6. A plot of a molecule of 3c showing the atom labelling scheme. Table S17. Crystallographically determined bond angles for 3c. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3696(4) C23 C24 1.387(3) Ru1 P1 1 2.3696(4) C24 C25 1.393(3) Ru1 P2 2.3465(4) C25 C26 1.393(2) Ru1 P2 1 2.3465(4) C31 C32 1.399(2) Ru1 C1 2.0648(16) C31 C36 1.397(2) Ru1 C1 1 2.0648(16) C32 C33 1.395(2) P1 C10 1.8484(16) C33 C34 1.388(3) P1 C21 1.8493(16) C34 C35 1.386(3) P1 C31 1.8347(16) C35 C36 1.391(2) P2 C11 1.8616(16) C41 C42 1.396(2) P2 C41 1.8375(16) C41 C46 1.393(2) P2 C51 1.8368(16) C42 C43 1.393(2) O1 C6 1.374(2) C43 C44 1.380(3) O1 C9 1.425(2) C44 C45 1.385(3) C1 C2 1.217(2) C45 C46 1.391(2) C2 C3 1.437(2) C51 C52 1.385(2) C3 C4 1.409(2) C51 C56 1.400(2) C3 C8 1.397(2) C52 C53 1.393(2) C4 C5 1.389(2) C53 C54 1.385(3) C5 C6 1.392(3) C54 C55 1.389(3) C6 C7 1.388(3) C55 C56 1.386(2) C7 C8 1.396(2) C1S C2S 1.394(3) C10 C11 1.523(2) C1S C3S 2 1.381(3) C21 C22 1.394(2) C2S C3S 1.387(3) C21 C26 1.406(2) C2S C4S 1.524(5) 46

C22 C23 1.397(2) C3S C1S 2 1.381(3) Table S18. Crystallographically determined bond angles for 3c. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 180.0 C11 C10 P1 106.73(11) P2 Ru1 P1 1 98.206(14) C10 C11 P2 110.78(11) P2 1 Ru1 P1 1 81.794(14) C22 C21 P1 122.20(12) P2 1 Ru1 P1 98.207(14) C22 C21 C26 118.50(15) P2 Ru1 P1 81.793(14) C26 C21 P1 119.29(12) P2 1 Ru1 P2 180.0 C21 C22 C23 120.45(16) C1 Ru1 P1 98.35(4) C24 C23 C22 120.68(17) C1 1 Ru1 P1 81.65(4) C23 C24 C25 119.50(17) C1 Ru1 P1 1 81.65(4) C24 C25 C26 120.05(17) C1 1 Ru1 P1 1 98.35(4) C25 C26 C21 120.82(17) C1 1 Ru1 P2 1 90.70(4) C32 C31 P1 120.51(12) C1 Ru1 P2 1 89.30(4) C36 C31 P1 120.76(13) C1 Ru1 P2 90.70(4) C36 C31 C32 118.68(15) C1 1 Ru1 P2 89.30(4) C33 C32 C31 120.48(16) C1 Ru1 C1 1 180.0 C34 C33 C32 120.20(17) C10 P1 Ru1 104.19(5) C35 C34 C33 119.67(16) C10 P1 C21 98.86(7) C34 C35 C36 120.41(16) C21 P1 Ru1 125.01(5) C35 C36 C31 120.56(16) C31 P1 Ru1 121.08(5) C42 C41 P2 120.53(12) C31 P1 C10 104.63(7) C46 C41 P2 121.06(13) C31 P1 C21 99.48(7) C46 C41 C42 118.24(15) C11 P2 Ru1 109.37(5) C43 C42 C41 120.68(16) C41 P2 Ru1 118.87(5) C44 C43 C42 120.47(16) C41 P2 C11 101.92(7) C43 C44 C45 119.40(16) C51 P2 Ru1 120.30(5) C44 C45 C46 120.36(17) C51 P2 C11 101.86(7) C45 C46 C41 120.82(16) C51 P2 C41 101.85(7) C52 C51 P2 120.65(12) C6 O1 C9 116.50(15) C52 C51 C56 118.42(15) C2 C1 Ru1 176.59(14) C56 C51 P2 120.93(12) C1 C2 C3 177.96(18) C51 C52 C53 121.07(16) C4 C3 C2 121.20(16) C54 C53 C52 119.96(17) C8 C3 C2 121.37(15) C53 C54 C55 119.61(17) C8 C3 C4 117.41(15) C56 C55 C54 120.20(17) C5 C4 C3 121.08(16) C55 C56 C51 120.73(16) C4 C5 C6 120.22(17) C3S 2 C1S C2S 120.9(2) O1 C6 C5 115.95(16) C1S C2S C4S 122.1(3) O1 C6 C7 124.11(16) C3S C2S C1S 118.2(2) C7 C6 C5 119.94(15) C3S C2S C4S 119.6(3) C6 C7 C8 119.46(16) C1S 2 C3S C2S 120.9(2) C7 C8 C3 121.88(16) 47

Table S19. Crystal and refinement data for trans-ru(c CC 6 H 4 CO 2 Me-4) 2 (dppe) 2 (3d) Empirical formula C 72 H 62 O 4 P 4 Ru x C 7 H 8 Formula weight 1308.30 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.3908(3) b/å 12.8371(4) c/å 13.8661(4) / 97.950(10) β/ 108.731(10) γ/ 92.244(10) Volume/Å 3 1561.58(8) Z 1 ρ calc mg/mm 3 1.391 m/mm -1 0.407 F(000) 680 Crystal size/mm 3 0.14 0.11 0.06 2Θ range for data collection 3.14 to 60 Index ranges -13 h 13, -18 k 18, -19 l 19 Reflections collected 20792 Independent reflections 9066[R(int) = 0.0440] Data/restraints/parameters 9066/0/539 Goodness-of-fit on F 2 0.969 Final R indexes [I>=2σ (I)] R 1 = 0.0347, wr 2 = 0.0667 Final R indexes [all data] R 1 = 0.0514, wr 2 = 0.0714 Largest diff. peak/hole / e Å -3 0.690/-0.641 48

Figure S7. A plot of a molecule of 3d showing the atom labelling scheme. Table S20. Crystallographically determined bond lengths for 3d. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3620(5) C22 C23 1.386(2) Ru1 P1 1 2.3620(5) C23 C24 1.384(3) Ru1 P2 1 2.3525(4) C24 C25 1.386(3) Ru1 P2 2.3525(4) C25 C26 1.389(3) Ru1 C1 2.0687(18) C31 C32 1.405(2) Ru1 C1 1 2.0687(18) C31 C36 1.395(2) P1 C11 1.8410(18) C32 C33 1.384(3) P1 C21 1.8318(17) C33 C34 1.386(3) P1 C31 1.8438(17) C34 C35 1.385(3) P2 C12 1.8565(18) C35 C36 1.388(2) P2 C41 1.8329(17) C41 C42 1.398(2) P2 C51 1.8398(17) C41 C46 1.392(2) O1 C9 1.349(2) C42 C43 1.389(3) O1 C10 1.441(2) C43 C44 1.385(3) O2 C9 1.210(2) C44 C45 1.382(3) C1 C2 1.197(2) C45 C46 1.387(3) C2 C3 1.443(2) C51 C52 1.397(2) C3 C4 1.400(3) C51 C56 1.391(2) C3 C8 1.408(3) C52 C53 1.385(3) C4 C5 1.387(2) C53 C54 1.389(3) C5 C6 1.392(3) C54 C55 1.383(3) C6 C7 1.386(3) C55 C56 1.389(3) C6 C9 1.482(2) C1S C2S 1.396(4) C7 C8 1.381(3) C1S C3S 2 1.388(4) 49

C11 C12 1.524(2) C1S C4S 1.506(5) C21 C22 1.394(2) C2S C3S 1.367(4) C21 C26 1.398(2) C3S C1S 2 1.388(4) Table S21. Crystallographically determined bond angles for 3d. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 180.0 O2 C9 O1 123.25(17) P2 1 Ru1 P1 1 83.268(17) O2 C9 C6 125.36(18) P2 Ru1 P1 1 96.732(17) C12 C11 P1 106.76(12) P2 Ru1 P1 83.269(18) C11 C12 P2 110.60(12) P2 1 Ru1 P1 96.732(17) C22 C21 P1 120.06(14) P2 Ru1 P2 1 180.0 C22 C21 C26 118.37(16) C1 1 Ru1 P1 98.25(5) C26 C21 P1 121.56(13) C1 Ru1 P1 81.75(5) C23 C22 C21 120.85(18) C1 1 Ru1 P1 1 81.75(5) C24 C23 C22 120.18(18) C1 Ru1 P1 1 98.25(5) C23 C24 C25 119.86(17) C1 1 Ru1 P2 93.45(5) C24 C25 C26 119.98(18) C1 Ru1 P2 86.55(5) C25 C26 C21 120.74(17) C1 Ru1 P2 1 93.45(5) C32 C31 P1 119.58(13) C1 1 Ru1 P2 1 86.55(5) C36 C31 P1 122.22(13) C1 Ru1 C1 1 180.00(8) C36 C31 C32 118.10(16) C11 P1 Ru1 104.42(6) C33 C32 C31 120.87(17) C11 P1 C31 98.74(8) C32 C33 C34 120.24(18) C21 P1 Ru1 120.01(6) C35 C34 C33 119.58(17) C21 P1 C11 104.21(8) C34 C35 C36 120.45(18) C21 P1 C31 100.78(8) C35 C36 C31 120.73(17) C31 P1 Ru1 125.05(6) C42 C41 P2 118.95(14) C12 P2 Ru1 107.78(6) C46 C41 P2 122.77(14) C41 P2 Ru1 121.12(6) C46 C41 C42 118.28(16) C41 P2 C12 101.16(8) C43 C42 C41 120.60(18) C41 P2 C51 100.88(8) C44 C43 C42 120.30(19) C51 P2 Ru1 120.60(6) C45 C44 C43 119.55(18) C51 P2 C12 102.24(8) C44 C45 C46 120.36(18) C9 O1 C10 116.76(18) C45 C46 C41 120.86(18) C2 C1 Ru1 174.79(15) C52 C51 P2 120.29(13) C1 C2 C3 171.72(19) C56 C51 P2 121.40(13) C4 C3 C2 122.74(16) C56 C51 C52 118.30(16) C4 C3 C8 117.91(16) C53 C52 C51 121.01(17) C8 C3 C2 119.25(16) C52 C53 C54 119.85(17) C5 C4 C3 121.08(17) C55 C54 C53 119.86(17) C4 C5 C6 120.23(18) C54 C55 C56 120.06(18) C5 C6 C9 119.78(17) C55 C56 C51 120.90(17) C7 C6 C5 119.14(17) C2S C1S C4S 122.1(3) C7 C6 C9 121.08(17) C3S 2 C1S C2S 118.6(2) C8 C7 C6 121.05(18) C3S 2 C1S C4S 119.2(3) C7 C8 C3 120.52(18) C3S C2S C1S 120.8(2) 50

O1 C9 C6 111.39(17) C2S C3S C1S 2 120.6(2) Table S22. Crystal and refinement data for trans-ru(c CC 6 H 4 C CSiMe 3-4) 2 (dppe) 2 (3f) Empirical formula C 78 H 74 Si 2 P 4 Ru Formula weight 1292.50 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.4265(4) b/å 13.5130(5) c/å 14.2919(6) / 76.253(2) β/ 74.292(3) γ/ 71.596(2) Volume/Å 3 1639.65(12) Z 1 ρ calc mg/mm 3 1.309 m/mm -1 0.417 F(000) 674 Crystal size/mm 3 0.51 0.06 0.03 2Θ range for data collection 3 to 57 Index ranges -12 h 12, -18 k 18, -19 l 19 Reflections collected 18597 Independent reflections 8224[R(int) = 0.0493] Data/restraints/parameters 8224/0/533 Goodness-of-fit on F 2 0.990 Final R indexes [I>=2σ (I)] R 1 = 0.0453, wr 2 = 0.1029 Final R indexes [all data] R 1 = 0.0711, wr 2 = 0.1119 Largest diff. peak/hole / e Å -3 1.015/-1.147 51

Figure S8. A plot of a molecule of 3f. Table S23. Crystallographically determined bond lengths for 3f. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3598(6) C14 C15 1.529(4) Ru1 P1 1 2.3598(6) C21 C22 1.391(4) Ru1 P2 1 2.3555(7) C21 C26 1.407(4) Ru1 P2 2.3555(7) C22 C23 1.390(4) Ru1 C1 1 2.066(3) C23 C24 1.383(4) Ru1 C1 2.066(3) C24 C25 1.396(4) P1 C14 1.850(3) C25 C26 1.379(4) P1 C21 1.849(3) C31 C32 1.403(4) P1 C31 1.835(3) C31 C36 1.396(4) P2 C15 1.861(3) C32 C33 1.389(4) P2 C41 1.828(3) C33 C34 1.385(4) P2 C51 1.837(3) C34 C35 1.379(5) Si1 C10 1.836(3) C35 C36 1.395(4) Si1 C11 1.858(4) C41 C42 1.399(4) Si1 C12 1.849(4) C41 C46 1.398(4) Si1 C13 1.853(4) C42 C43 1.378(4) C1 C2 1.204(4) C43 C44 1.391(5) C2 C3 1.438(4) C44 C45 1.381(5) C3 C4 1.403(4) C45 C46 1.387(4) C3 C8 1.402(4) C51 C52 1.398(4) C4 C5 1.380(4) C51 C56 1.392(4) C5 C6 1.398(4) C52 C53 1.391(4) C6 C7 1.405(4) C53 C54 1.376(4) C6 C9 1.449(4) C54 C55 1.392(4) C7 C8 1.379(4) C55 C56 1.386(4) 52

C9 C10 1.197(4) Table S24. Crystallographically determined bond angles for 3f. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 180.0 C5 C6 C9 121.4(3) P2 1 Ru1 P1 1 82.75(2) C7 C6 C9 120.0(3) P2 Ru1 P1 1 97.25(2) C8 C7 C6 120.6(3) P2 Ru1 P1 82.76(2) C7 C8 C3 121.2(3) P2 1 Ru1 P1 97.24(2) C10 C9 C6 177.4(4) P2 Ru1 P2 1 180.0 C9 C10 Si1 171.3(4) C1 1 Ru1 P1 80.11(7) C15 C14 P1 106.74(18) C1 Ru1 P1 99.89(7) C14 C15 P2 110.93(18) C1 1 Ru1 P1 1 99.89(7) C22 C21 P1 121.73(19) C1 Ru1 P1 1 80.11(7) C22 C21 C26 118.4(2) C1 Ru1 P2 92.01(7) C26 C21 P1 119.8(2) C1 1 Ru1 P2 87.99(7) C23 C22 C21 120.6(2) C1 1 Ru1 P2 1 92.01(7) C24 C23 C22 120.4(3) C1 Ru1 P2 1 87.99(7) C23 C24 C25 119.7(3) C1 1 Ru1 C1 180.0 C26 C25 C24 119.9(3) C14 P1 Ru1 105.44(9) C25 C26 C21 121.0(3) C21 P1 Ru1 123.92(8) C32 C31 P1 120.5(2) C21 P1 C14 98.52(12) C36 C31 P1 121.1(2) C31 P1 Ru1 121.37(8) C36 C31 C32 118.4(3) C31 P1 C14 103.47(12) C33 C32 C31 120.4(3) C31 P1 C21 100.24(12) C34 C33 C32 120.7(3) C15 P2 Ru1 108.61(9) C35 C34 C33 119.3(3) C41 P2 Ru1 120.34(9) C34 C35 C36 120.8(3) C41 P2 C15 101.52(12) C35 C36 C31 120.4(3) C41 P2 C51 102.01(12) C42 C41 P2 119.9(2) C51 P2 Ru1 119.78(9) C46 C41 P2 122.2(2) C51 P2 C15 101.69(12) C46 C41 C42 117.9(3) C10 Si1 C11 105.38(17) C43 C42 C41 121.2(3) C10 Si1 C12 112.65(19) C42 C43 C44 120.4(3) C10 Si1 C13 107.93(16) C45 C44 C43 119.2(3) C12 Si1 C11 109.8(2) C44 C45 C46 120.6(3) C12 Si1 C13 108.29(18) C45 C46 C41 120.7(3) C13 Si1 C11 112.80(18) C52 C51 P2 120.5(2) C2 C1 Ru1 175.3(2) C56 C51 P2 121.5(2) C1 C2 C3 177.1(3) C56 C51 C52 118.0(3) C4 C3 C2 120.6(3) C53 C52 C51 120.9(3) C8 C3 C2 121.7(3) C54 C53 C52 120.2(3) C8 C3 C4 117.7(3) C53 C54 C55 119.7(3) C5 C4 C3 121.5(3) C56 C55 C54 120.0(3) C4 C5 C6 120.3(3) C55 C56 C51 121.2(3) C5 C6 C7 118.6(3) 53

Table S25. Crystal and refinement data for trans-ru(c CC 6 H 4 C CCMe 3-4) 2 (dppe) 2 (3g) Empirical formula C 84 H 78 Br 0.1 Cl 12 P 4 Ru Formula weight 1745.80 Temperature/K 120.0 Crystal system triclinic Space group P-1 a/å 10.8015(4) b/å 12.4654(4) c/å 16.4565(6) / 94.8960(10) β/ 105.1080(10) γ/ 103.0040(10) Volume/Å 3 2059.77(13) Z 1 ρ calc mg/mm 3 1.407 m/mm -1 0.749 F(000) 894 Crystal size/mm 3 0.54 0.08 0.08 Theta range for data collection 2.6 to 59 Index ranges -14 h 14, -17 k 17, -22 l 22 Reflections collected 35554 Independent reflections 11468[R(int) = 0.0314] Data/restraints/parameters 11468/1/464 Goodness-of-fit on F 2 1.083 Final R indexes [I>2σ (I)] R 1 = 0.0429, wr 2 = 0.1067 Final R indexes [all data] R 1 = 0.0543, wr 2 = 0.1141 Largest diff. peak/hole / e Å -3 1.404/-1.194 54

Figure S9. A plot of a molecule of 3g showing the atom labelling scheme. Table S26. Crystallographically determined bond lengths for 3g. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3548(5) C21 C26 1.385(3) Ru1 P1 1 2.3548(5) C22 C23 1.386(3) Ru1 P2 2.3604(5) C23 C24 1.378(4) Ru1 P2 1 2.3604(5) C24 C25 1.387(4) Ru1 C1 2.057(2) C25 C26 1.390(3) Ru1 C1 1 2.057(2) C31 C32 1.395(3) Br7 C6 1.886(7) C31 C36 1.394(3) P1 C15 1.860(2) C32 C33 1.394(3) P1 C21 1.832(2) C33 C34 1.383(4) P1 C31 1.836(2) C34 C35 1.381(4) P2 C16 1.845(2) C35 C36 1.393(3) P2 C41 1.832(2) C41 C42 1.394(3) P2 C51 1.845(2) C41 C46 1.395(3) C1 C2 1.211(3) C42 C43 1.392(3) C2 C3 1.431(3) C43 C44 1.379(4) C3 C4 1.410(3) C44 C45 1.383(4) C3 C8 1.405(3) C45 C46 1.391(3) C4 C5 1.383(3) C51 C52 1.403(3) C5 C6 1.398(4) C51 C56 1.395(3) C6 C7 1.404(4) C52 C53 1.387(3) C6 C9 1.473(4) C53 C54 1.387(3) C7 C8 1.383(3) C54 C55 1.386(3) C9 C10 1.159(3) C55 C56 1.393(3) C10 C11 1.486(4) Cl1 C1S 1.757(3) 55

C11 C12 1.564(5) Cl2 C1S 1.747(3) C11 C13 1.549(4) Cl3 C1S 1.754(3) C11 C14 1.532(4) Cl4 C2S 1.748(5) C15 C16 1.527(3) Cl5 C2S 1.772(5) C21 C22 1.397(3) Cl6 C2S 1.749(4) Table S27. Crystallographically determined bond angles for 3g. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 180.000(19) C10 C11 C13 109.9(2) P1 1 Ru1 P2 97.077(17) C10 C11 C14 109.4(2) P1 Ru1 P2 82.923(17) C13 C11 C12 108.1(2) P1 1 Ru1 P2 1 82.924(17) C14 C11 C12 110.8(3) P1 Ru1 P2 1 97.076(17) C14 C11 C13 110.3(2) P2 Ru1 P2 1 179.999(1) C16 C15 P1 109.72(14) C1 1 Ru1 P1 1 88.50(5) C15 C16 P2 106.66(14) C1 Ru1 P1 88.50(5) C22 C21 P1 121.49(17) C1 1 Ru1 P1 91.50(6) C26 C21 P1 120.28(15) C1 Ru1 P1 1 91.50(5) C26 C21 C22 118.2(2) C1 1 Ru1 P2 1 80.55(5) C23 C22 C21 120.6(2) C1 Ru1 P2 80.55(5) C24 C23 C22 120.6(2) C1 1 Ru1 P2 99.45(5) C23 C24 C25 119.4(2) C1 Ru1 P2 1 99.45(5) C24 C25 C26 120.0(2) C1 Ru1 C1 1 179.998(1) C21 C26 C25 121.1(2) C15 P1 Ru1 108.29(7) C32 C31 P1 119.25(16) C21 P1 Ru1 118.78(7) C36 C31 P1 122.08(17) C21 P1 C15 102.32(10) C36 C31 C32 118.7(2) C21 P1 C31 101.92(10) C33 C32 C31 120.7(2) C31 P1 Ru1 122.05(7) C34 C33 C32 119.9(2) C31 P1 C15 100.41(10) C35 C34 C33 119.9(2) C16 P2 Ru1 104.80(7) C34 C35 C36 120.4(2) C16 P2 C51 98.66(9) C35 C36 C31 120.3(2) C41 P2 Ru1 121.10(7) C42 C41 P2 121.05(16) C41 P2 C16 103.79(9) C42 C41 C46 118.54(19) C41 P2 C51 100.06(9) C46 C41 P2 120.41(16) C51 P2 Ru1 124.60(7) C43 C42 C41 120.5(2) C2 C1 Ru1 176.39(17) C44 C43 C42 120.4(2) C1 C2 C3 177.8(2) C43 C44 C45 119.7(2) C4 C3 C2 120.8(2) C44 C45 C46 120.2(2) C8 C3 C2 121.6(2) C45 C46 C41 120.6(2) C8 C3 C4 117.5(2) C52 C51 P2 119.24(16) C5 C4 C3 121.2(2) C56 C51 P2 122.40(15) C4 C5 C6 120.7(2) C56 C51 C52 118.31(19) C5 C6 Br7 135.0(3) C53 C52 C51 120.6(2) C5 C6 C7 118.5(2) C54 C53 C52 120.5(2) C5 C6 C9 119.9(2) C55 C54 C53 119.4(2) C7 C6 Br7 106.4(3) C54 C55 C56 120.4(2) C7 C6 C9 121.6(2) C55 C56 C51 120.7(2) 56

C9 C6 Br7 15.5(2) Cl2 C1S Cl1 111.22(16) C8 C7 C6 120.8(2) Cl2 C1S Cl3 110.70(15) C7 C8 C3 121.2(2) Cl3 C1S Cl1 110.81(14) C10 C9 C6 178.7(3) Cl4 C2S Cl5 110.31(19) C9 C10 C11 178.7(3) Cl4 C2S Cl6 110.6(3) C10 C11 C12 108.3(2) Cl6 C2S Cl5 111.2(2) Table S28. Crystal and refinement data for trans-ru(c CC 6 H 4 NH 2-4) 2 (dppe) 2 (3h) Empirical formula C 68 H 60 N 2 P 4 Ru Formula weight 1130.13 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.3537(3) b/å 12.9960(4) c/å 13.4808(4) / 117.1640(10) β/ 95.6320(10) γ/ 103.7080(10) Volume/Å 3 1375.51(7) Z 1 ρ calc mg/mm 3 1.364 m/mm -1 0.446 F(000) 586.0 Crystal size/mm 3 0.29 0.08 0.07 2Θ range for data collection 3.5 to 59 Index ranges -12 h 12, -18 k 18, -18 l 18 Reflections collected 17825 Independent reflections 7635[R(int) = 0.0347] Data/restraints/parameters 7635/0/460 Goodness-of-fit on F 2 1.041 Final R indexes [I>=2σ (I)] R 1 = 0.0390, wr 2 = 0.0911 Final R indexes [all data] R 1 = 0.0511, wr 2 = 0.0992 Largest diff. peak/hole / e Å -3 0.80/-0.79 57

Figure S10. A plot of a molecule of 3h showing the atom labelling scheme. Table S29. Crystallographically determined bond lengths for 3h. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3488(5) C11 C16 1.397(3) Ru1 P1 1 2.3487(5) C12 C13 1.391(3) Ru1 P2 1 2.3496(5) C13 C14 1.382(3) Ru1 P2 2.3496(5) C14 C15 1.392(3) Ru1 C1 2.074(2) C15 C16 1.386(3) Ru1 C1 1 2.074(2) C21 C22 1.389(3) P1 C9 1.859(2) C21 C26 1.388(3) P1 C11 1.840(2) C22 C23 1.396(3) P1 C21 1.837(2) C23 C24 1.376(4) P2 C10 1.842(2) C24 C25 1.381(4) P2 C31 1.847(2) C25 C26 1.391(3) P2 C41 1.837(2) C31 C32 1.392(3) N1 C6 1.417(3) C31 C36 1.401(3) C1 C2 1.197(3) C32 C33 1.394(3) C2 C3 1.445(3) C33 C34 1.386(3) C3 C4 1.398(3) C34 C35 1.389(3) C3 C8 1.400(3) C35 C36 1.385(3) C4 C5 1.387(4) C41 C42 1.397(3) C5 C6 1.384(4) C41 C46 1.397(3) C6 C7 1.386(4) C42 C43 1.390(3) C7 C8 1.391(3) C43 C44 1.390(4) C9 C10 1.522(3) C44 C45 1.379(4) C11 C12 1.389(3) C45 C46 1.386(3) 58

Table S30. Crystallographically determined bond angles for 3h. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 180.0 C6 C7 C8 120.8(2) P1 1 Ru1 P2 97.168(18) C7 C8 C3 121.4(2) P1 Ru1 P2 82.832(18) C10 C9 P1 110.48(14) P1 1 Ru1 P2 1 82.832(18) C9 C10 P2 106.60(14) P1 Ru1 P2 1 97.167(18) C12 C11 P1 120.85(16) P2 Ru1 P2 1 180.00(2) C12 C11 C16 118.46(19) C1 Ru1 P1 1 87.94(6) C16 C11 P1 120.68(16) C1 1 Ru1 P1 87.94(6) C11 C12 C13 120.9(2) C1 Ru1 P1 92.06(6) C14 C13 C12 120.2(2) C1 1 Ru1 P1 1 92.06(6) C13 C14 C15 119.5(2) C1 Ru1 P2 1 80.72(6) C16 C15 C14 120.2(2) C1 1 Ru1 P2 80.72(6) C15 C16 C11 120.8(2) C1 Ru1 P2 99.28(6) C22 C21 P1 121.95(17) C1 1 Ru1 P2 1 99.28(6) C26 C21 P1 119.65(17) C1 1 Ru1 C1 180.00(11) C26 C21 C22 118.4(2) C9 P1 Ru1 108.32(7) C21 C22 C23 120.8(2) C11 P1 Ru1 120.00(7) C24 C23 C22 120.2(2) C11 P1 C9 102.36(10) C23 C24 C25 119.5(2) C21 P1 Ru1 121.08(7) C24 C25 C26 120.4(3) C21 P1 C9 101.00(10) C21 C26 C25 120.7(2) C21 P1 C11 101.12(10) C32 C31 P2 122.50(16) C10 P2 Ru1 105.02(7) C32 C31 C36 118.22(19) C10 P2 C31 98.91(10) C36 C31 P2 119.26(16) C31 P2 Ru1 124.88(7) C31 C32 C33 120.9(2) C41 P2 Ru1 120.45(7) C34 C33 C32 120.2(2) C41 P2 C10 104.24(10) C33 C34 C35 119.5(2) C41 P2 C31 99.79(9) C36 C35 C34 120.2(2) C2 C1 Ru1 174.24(19) C35 C36 C31 121.0(2) C1 C2 C3 176.6(2) C42 C41 P2 120.20(16) C4 C3 C2 121.5(2) C46 C41 P2 121.35(16) C4 C3 C8 117.0(2) C46 C41 C42 118.45(19) C8 C3 C2 121.5(2) C43 C42 C41 120.8(2) C5 C4 C3 121.3(3) C44 C43 C42 119.9(2) C6 C5 C4 121.1(3) C45 C44 C43 119.8(2) C5 C6 N1 121.7(3) C44 C45 C46 120.6(2) C5 C6 C7 118.4(2) C45 C46 C41 120.5(2) C7 C6 N1 119.9(3) 59

Table S31. Crystal and refinement data for trans-ru(c CC 6 H 4 C CH-4) 2 (dppe) 2 (3i) Empirical formula C 72 H 58 P 4 Ru x CH 2 Cl 2 Formula weight 1233.06 Temperature/K 120 Crystal system triclinic Space group P-1 a/å 9.6711(2) b/å 12.9728(3) c/å 23.8066(6) / 81.220(10) β/ 86.794(10) γ/ 83.989(10) Volume/Å 3 2933.15(12) Z 2 ρ calc mg/mm 3 1.396 m/mm -1 0.512 F(000) 1272 Crystal size/mm 3 0.34 0.08 0.02 2Θ range for data collection 3.2 to 58 Index ranges -13 h 13, -17 k 17, -32 l 32 Reflections collected 48867 Independent reflections 15586[R(int) = 0.0528] Data/restraints/parameters 15586/0/724 Goodness-of-fit on F 2 1.038 Final R indexes [I>=2σ (I)] R 1 = 0.0439, wr 2 = 0.1027 Final R indexes [all data] R 1 = 0.0732, wr 2 = 0.1156 Largest diff. peak/hole / e Å -3 0.825/-1.182 60

Figure S10. A plot of a molecule of 3i showing the atom labelling scheme. Table S32. Crystallographically determined bond lengths for 3i. Atom Atom Length/Å Atom Atom Length/Å Ru1 P1 2.3616(7) Ru2 P3 2.3458(7) Ru1 P1 1 2.3615(7) Ru2 P4 2.3616(7) Ru1 P2 2.3517(7) Ru2 P4 2 2.3616(7) Ru1 P2 1 2.3517(7) Ru2 C101 2 2.062(3) Ru1 C1 2.061(3) Ru2 C101 2.062(3) Ru1 C1 1 2.061(3) P3 C111 1.835(3) P1 C11 1.846(3) P3 C121 1.835(3) P1 C21 1.829(3) P3 C131 1.834(3) P1 C31 1.848(3) P4 C112 1.863(3) P2 C12 1.853(3) P4 C141 1.852(3) P2 C41 1.837(3) P4 C151 1.832(3) P2 C51 1.834(3) C101 C102 1.209(4) C1 C2 1.212(4) C102 C103 1.437(4) C2 C3 1.435(4) C103 C104 1.398(4) C3 C4 1.395(4) C103 C108 1.407(4) C3 C8 1.405(4) C104 C105 1.391(4) C4 C5 1.384(4) C105 C106 1.399(4) C5 C6 1.391(5) C106 C107 1.386(4) C6 C7 1.404(5) C106 C109 1.460(4) C6 C9 1.444(4) C107 C108 1.382(4) C7 C8 1.385(4) C109 C110 1.145(5) C9 C10 1.161(5) C111 C112 1.535(4) C11 C12 1.526(4) C121 C122 1.387(4) C21 C22 1.398(4) C121 C126 1.400(4) 61

C21 C26 1.399(4) C122 C123 1.390(4) C22 C23 1.385(4) C123 C124 1.379(5) C23 C24 1.376(4) C124 C125 1.389(5) C24 C25 1.376(4) C125 C126 1.383(5) C25 C26 1.390(4) C131 C132 1.391(4) C31 C32 1.405(4) C131 C136 1.400(4) C31 C36 1.394(4) C132 C133 1.393(4) C32 C33 1.387(4) C133 C134 1.371(5) C33 C34 1.386(4) C134 C135 1.385(5) C34 C35 1.381(4) C135 C136 1.378(4) C35 C36 1.393(4) C141 C142 1.395(4) C41 C42 1.392(4) C141 C146 1.403(4) C41 C46 1.390(4) C142 C143 1.399(4) C42 C43 1.382(4) C143 C144 1.375(5) C43 C44 1.379(5) C144 C145 1.379(5) C44 C45 1.374(5) C145 C146 1.396(4) C45 C46 1.400(4) C151 C152 1.398(4) C51 C52 1.402(4) C151 C156 1.390(4) C51 C56 1.387(4) C152 C153 1.386(4) C52 C53 1.386(4) C153 C154 1.373(5) C53 C54 1.376(4) C154 C155 1.385(5) C54 C55 1.387(4) C155 C156 1.392(4) C55 C56 1.389(4) Cl1 C1S 1.748(4) Ru2 P3 2 2.3458(7) Cl2 C1S 1.728(4) Table S33. Crystallographically determined bond angles for 3i. Atom Atom Atom Angle/ Atom Atom Atom Angle/ P1 1 Ru1 P1 179.999(1) P3 Ru2 P4 82.06(3) P2 Ru1 P1 1 97.24(2) P3 2 Ru2 P4 97.94(3) P2 1 Ru1 P1 1 82.76(2) P3 2 Ru2 P4 2 82.06(3) P2 1 Ru1 P1 97.24(2) P3 Ru2 P4 2 97.94(3) P2 Ru1 P1 82.76(2) P4 Ru2 P4 2 180.00(3) P2 1 Ru1 P2 179.999(1) C101 2 Ru2 P3 2 95.40(8) C1 Ru1 P1 81.01(7) C101 Ru2 P3 95.40(8) C1 1 Ru1 P1 98.99(7) C101 2 Ru2 P3 84.60(8) C1 Ru1 P1 1 98.99(7) C101 Ru2 P3 2 84.60(8) C1 1 Ru1 P1 1 81.01(7) C101 Ru2 P4 94.84(8) C1 1 Ru1 P2 1 87.18(7) C101 2 Ru2 P4 85.16(8) C1 Ru1 P2 1 92.82(7) C101 Ru2 P4 2 85.16(8) C1 Ru1 P2 87.18(7) C101 2 Ru2 P4 2 94.84(8) C1 1 Ru1 P2 92.82(7) C101 2 Ru2 C101 180.000(3) C1 Ru1 C1 1 180.0 C111 P3 Ru2 105.85(9) C11 P1 Ru1 104.56(8) C121 P3 Ru2 122.30(10) C11 P1 C31 98.29(12) C121 P3 C111 101.67(13) C21 P1 Ru1 121.33(9) C131 P3 Ru2 117.11(9) C21 P1 C11 104.18(12) C131 P3 C111 104.68(13) 62

C21 P1 C31 100.14(12) C131 P3 C121 102.97(13) C31 P1 Ru1 124.49(9) C112 P4 Ru2 109.02(10) C12 P2 Ru1 108.45(9) C141 P4 Ru2 123.14(9) C41 P2 Ru1 119.59(9) C141 P4 C112 97.77(13) C41 P2 C12 101.87(12) C151 P4 Ru2 116.79(9) C51 P2 Ru1 120.84(9) C151 P4 C112 103.55(13) C51 P2 C12 101.43(12) C151 P4 C141 103.43(13) C51 P2 C41 101.76(12) C102 C101 Ru2 178.6(2) C2 C1 Ru1 174.3(2) C101 C102 C103 172.6(3) C1 C2 C3 174.2(3) C104 C103 C102 121.4(3) C4 C3 C2 120.8(3) C104 C103 C108 117.6(3) C4 C3 C8 117.8(3) C108 C103 C102 121.0(3) C8 C3 C2 121.3(3) C105 C104 C103 121.1(3) C5 C4 C3 121.0(3) C104 C105 C106 120.4(3) C4 C5 C6 121.0(3) C105 C106 C109 120.0(3) C5 C6 C7 118.7(3) C107 C106 C105 118.9(3) C5 C6 C9 120.7(3) C107 C106 C109 121.1(3) C7 C6 C9 120.5(3) C108 C107 C106 120.8(3) C8 C7 C6 120.0(3) C107 C108 C103 121.3(3) C7 C8 C3 121.4(3) C110 C109 C106 178.1(4) C10 C9 C6 177.4(5) C112 C111 P3 108.98(18) C12 C11 P1 106.53(18) C111 C112 P4 112.76(19) C11 C12 P2 110.44(18) C122 C121 P3 119.2(2) C22 C21 P1 120.9(2) C122 C121 C126 118.8(3) C22 C21 C26 118.0(2) C126 C121 P3 121.9(2) C26 C21 P1 121.1(2) C121 C122 C123 120.7(3) C23 C22 C21 120.6(3) C124 C123 C122 120.0(3) C24 C23 C22 120.7(3) C123 C124 C125 119.9(3) C23 C24 C25 119.6(3) C126 C125 C124 120.2(3) C24 C25 C26 120.4(3) C125 C126 C121 120.3(3) C25 C26 C21 120.6(3) C132 C131 P3 123.7(2) C32 C31 P1 118.9(2) C132 C131 C136 118.6(3) C36 C31 P1 122.7(2) C136 C131 P3 117.6(2) C36 C31 C32 118.3(2) C131 C132 C133 120.0(3) C33 C32 C31 120.6(3) C134 C133 C132 120.8(3) C34 C33 C32 120.3(3) C133 C134 C135 119.6(3) C35 C34 C33 119.8(3) C136 C135 C134 120.5(3) C34 C35 C36 120.3(3) C135 C136 C131 120.5(3) C35 C36 C31 120.6(3) C142 C141 P4 124.4(2) C42 C41 P2 119.4(2) C142 C141 C146 118.3(3) C46 C41 P2 121.8(2) C146 C141 P4 117.1(2) C46 C41 C42 118.7(3) C141 C142 C143 120.9(3) C43 C42 C41 121.1(3) C144 C143 C142 119.6(3) C44 C43 C42 119.9(3) C143 C144 C145 120.8(3) C45 C44 C43 119.9(3) C144 C145 C146 119.9(3) C44 C45 C46 120.6(3) C145 C146 C141 120.5(3) C41 C46 C45 119.8(3) C152 C151 P4 120.5(2) C52 C51 P2 120.5(2) C156 C151 P4 121.2(2) 63

C56 C51 P2 121.2(2) C156 C151 C152 118.2(3) C56 C51 C52 118.3(2) C153 C152 C151 120.8(3) C53 C52 C51 120.5(3) C154 C153 C152 120.7(3) C54 C53 C52 120.4(3) C153 C154 C155 119.2(3) C53 C54 C55 119.8(3) C154 C155 C156 120.5(3) C54 C55 C56 119.9(3) C151 C156 C155 120.6(3) C51 C56 C55 121.0(3) Cl2 C1S Cl1 113.4(2) P3 Ru2 P3 2 180.0 IR SPECTROELECTROCHEMICAL DATA Calculated (top) and experimental (bottom) IR spectrum in neutral state (black line) and first oxidized state (red dotted line) for 3f, 3h, 4a and 4b. (3f) trans-ru(c CC 6 H 4 C CSiMe 3-4) 2 (dppe) 2 64

(3h) trans-ru(c CC 6 H 4 NH 2-4) 2 (dppe) 2 : (4) trans-ru(c CC 6 H 4 C CSiMe 3-4)(C CC 6 H 4 NH 2-4)(dppe) 2 : 65

(5) trans-ru(c CC 6 H 4 CO 2 Me-4)(C CC 6 H 4 NH 2-4)(dppe) 2 : 66

Uv-Vis-NIR SPECTROELECTROCHEMICAL DATA (3f) trans-ru(c CC 6 H 4 C CSiMe 3-4) 2 (dppe) 2 : (3h) trans-ru(c CC 6 H 4 NH 2-4) 2 (dppe) 2 : 67

(4) trans-ru(c CC 6 H 4 C CSiMe 3-4)(C CC 6 H 4 NH 2-4)(dppe) 2 : (5) trans-ru(c CC 6 H 4 CO 2 Me-4)(C CC 6 H 4 NH 2-4)(dppe) 2 : 68

Table S32. Computed energy difference to the most stable rotamer (θ 0 Ω 0 ), ΔE, spin expectation value <S 2 >, characteristic vibrational frequencies ν, electronic excitation energies E trans below 20000 cm - 1 with corresponding transition dipole moment µ trans >1 D for [3f] +. a [3f] + in- plane perp out- of- plane θ 0 Ω 0 θ 0 Ω 90 θ 90 Ω 0 E [kj/mol] 0.0 1.9 <S 2 > 0.79 0.79 ν (C C) [cm - 1 ] 2180 (w) 2177 (w) 2034 (w) 2181 (w) 2178 (w) 2064 (w) ν (Ru- C C) [cm - 1 ] 1981 (vs) 1975 (vs) ν (C=C aryl ) [cm - 1 ] 1484 (w) 1596 (w) 1485 (w) E trans [cm - 1 ] (µ trans [D]) 11316 (9.7) 12287 (8.1) - 328 (0.6) orbital contribution 322 β =>323 β 321 β =>323 β 321 β =>323 β 19475 (1.9) 7312 (1.0) 319 β =>323 β 316 β =>323 β 10860 (10.3) 322 β =>323 β a Ground- state properties from TURBOMOLE 6.4, TDDFT excitations from Gaussian09. 69

Table S33. Orbital energies (E orb ) and Mulliken fragment spin- density (SD) contributions for the different conformations of [3f] +. in- plane- [3f] + (θ 0 Ω 0 ) perp- [3f] + (θ 0 Ω 90 ) E Orb Contribution [%] E Orb Contribution [%] MO [ev] Me 3 SiC C C C [Ru] C C C CC 6 H 4 [ev] Me 3 SiC C C C [Ru] C C C CC 6 H 4 C 6 H 4 SiMe 3 C 6 H 4 SiMe 3 SD / 7 11 71 6 5 / 9 13 74 6-2 324 β* - 1.35 2 0 70 0 1-1.38 0 0 81 0 0 * - 1.52 0 0 83 0 0-1.57 0 0 83 0 0 323 β* - 3.75 11 15 50 10 8-3.72 13 18 54 9 0-6.52 33 20 10 13 19-6.50 0 3 12 29 49 322 β - 6.47 25 19 8 18 23-6.41 0 7 19 28 41-6.74 25 10 7 16 33-6.65 57 29 7 1 0 321 β - 6.81 0 30 41 21 0-6.75 39 21 17 13 0-7.04 0 32 34 23 0-7.26 0 2 59 18 0 320 β - 7.22 31 5 13 5 29-7.25 0 35 24 3 19 Α - 7.44 0 0 74 0 7-7.39 0 42 27 2 11 319 β - 7.44 0 0 69 1 13-7.41 13 5 59 3 0-7.52 0 9 70 6 0-7.62 0 0 77 2 6 318 β - 7.52 0 9 69 7 0-7.63 0 0 76 0 5-7.70 8 0 81 0 0-7.72 6 1 79 0 0 70

out- of- plane- [3f] + (θ 90 Ω 0 ) E Orb Contribution [%] MO [ev] Me 3 SiC C C 6 H 4 C C [Ru] C C C CC 6 H 4 SiMe 3 SD / -1 11 84 7-2 324 β* -1.49 0 0 84 0 0 * -1.71 0 0 83 0 0 323 β* -3.64 0 15 65 12 0-6.40 33 22 13 12 15 322 β -6.29 27 21 18 13 15-6.74 24 10 0 17 39 321 β -6.75 26 11 1 17 37-7.34 0 0 66 16 0 320 β -7.22 0 16 47 15 0-7.51 2 44 36 7 0 319 β -7.64 0 10 74 0 0-7.67 0 0 83 0 1 318 β -7.70 0 4 77 0 3-7.78 9 1 70 6 0 71

Figure S11. Computed potential energy surface [3h] + {in kj/mol; BLYP35/COSMO (CH 2 Cl 2 ) level} Table S34. Computed energy difference to the most stable rotamer (θ 0 Ω = 20 ), ΔE, spin expectation value <S 2 > and excitation energies E trans below 20000 cm -1 with corresponding transition dipole moment m trans >1 D for selected points on the PES of [3h] +. a [3h] + θ 0 Ω = 90 θ 90 Ω = 0 E [kj/mol] 2.5 3.2 <S 2 > 0.78 0.78 E trans [cm -1 ] (µ trans [D]) 9900 (10.0) 7849 (12.1) orbital contribution 277 β=>279 β 278 β=>279 β 19139 (1.3) 11959 (1.5) 275 β=>279 β 273 β=>279 β a Ground-state properties from TURBOMOLE 6.4, TDDFT excitations from Gaussian09. 72