Supporting Material. Hydrogen Oxidation and Production Using Nickel-Based Molecular Catalysts with Positioned Proton Relays

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1 Supporting Material Hydrogen Oxidation and Production Using Nickel-Based Molecular Catalysts with Positioned Proton Relays Aaron D. Wilson, Rachel H. Newell, Michael J. McNevin, James T. Muckerman, ψ M. Rakowski DuBois,* and Daniel L. DuBois* Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado ψ Brookhaven National Lab, P.O. Box 5000, Upton, NY National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO Table of Contents Table of Contents S1 Thermodynamic hydride acceptor ability of [Ni(P Ph 2N Ph 2) 2 ] 2+ in acetonitrile S2 Determination of the rate constant for H 2 production from the catalytic current S2 Figure S1. Plot of the catalytic current for hydrogen production versus the concentration of 6a. S3 Figure S2. Plot of the slopes shown in Figure 5 vs 1/ν 1/2. S4 Figure S3. Cyclic voltammograms as a function of the concentration of 6b in the presence of 0.8 atm of H 2 and M NEt 3. S4 Figure S4. Plot of i c /i p for a 6.2 x 10-4 M solution of 6b as a function of the square root of H 2 pressure S5 Table S1. Crystal Data for [Ni(P Ph 2N Ph 2) 2 (MeCN)](BF 4 ) 2 (6a) and [Ni(P Cy 2N Bz 2) 2 ]- (BF 4 ) 2 2(MeCN) (6b) S5 Table S2. Atomic coordinates for [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)](BF 4 ) 2, 6a S6 Table S3. Bond lengths [Å] and angles [ ] for [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)](BF 4 ) 2, 6a S7 Figure S5. Atom numbering scheme for [Ni(P Ph 2N Ph 2) 2 (MeCN)](BF 4 ) 2, 6a S12 Table S4. Anisotropic displacement parameters (Å 2 x 10 3 ) for [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)](BF 4 ) 2, 6a S12 Table S5. Hydrogen coordinates ( x 10 4 ) and isotropic displacement parameters (Å 2 x 10 3 ) for [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)](BF 4 ) 2, 6a S14 Table S6. Torsion angles [ ] for [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)](BF 4 ) 2, 6a S15 Table S7. Atomic coordinates for [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN), 6b S19 Table S8. Bond lengths [Å] and angles [ ] for [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN), 6b S20 Figure S6. Atom numbering scheme for [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN), 6b S22 Table S9. Anisotropic displacement parameters (Å 2 x 10 3 ) for [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN), 6b S22 S1

2 Table S10. Hydrogen coordinates ( x 10 4 ) and isotropic displacement parameters (Å 2 x 10 3 ) for [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN), 6b S23 Table S11. Torsion angles [ ] for [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN), 6b S24 Details of the theoretical calculations S26 Table S12. Cartesian coordinates (XYZ file) of the optimized model catalyst [Ni(PH 2 CH 2 NHCH 2 PH 2 ) 2 ] 2+ S26 Table S13. Cartesian coordinates (XYZ file) of the optimized transition state for the heterolytic cleavage of dihydrogen to form [HNi(PH 2 CH 2 N(H)HCH 2 PH 2 )- (PH 2 CH 2 NHCH 2 PH 2 )] 2+ (9) S27 References for Supporting Information S28 Thermodynamic hydride acceptor ability of [Ni(P Ph 2N Ph 2) 2 ] 2+ in acetonitrile. The sum of reactions 1S-3S in Scheme 1S below is the reaction of [Ni(P Ph 2N Ph 2) 2 ] 2+ with a solvated hydride ion to form [HNi(P Ph 2N Ph 2) 2 ] + in acetonitrile (reaction 4S). Therefore, the sum of the free energies associated with each of these three reactions is the free energy associated with reaction 4S, or the hydride acceptor ability of [Ni(P Ph 2N Ph 2) 2 ] 2+ in acetonitrile. The free energy of reaction 1S (reaction 2 of the manuscript) is -RTlnK eq or 1.37pK eq. The equilibrium constant for reaction 1S of 0.30 ± 0.06 atm -1 {K = [8a] [p-ncc 6 H 4 NH 3+ ]/([6b] P H2 [p-ncc 6 H 4 NH 2 ])} corresponds to a free energy of 0.7 ± 0.2 kcal/mol using 1 atm of hydrogen as the standard state. The pk a value of anisidine for reaction 2S is 11.3 ± corresponding to a free energy of 15.5 ± 0.2 kcal/mol. Finally, the free energy for the conversion of 1.0 mole of solvated H + and H - in acetonitrile to 1.0 mole of H 2 gas is kcal/mol. 2 The sum of these three free energies gives a value of ± 0.4 kcal/mol for the hydride acceptor ability of [Ni(P Ph 2N Ph 2)] 2+. Reaction ΔG (kcal/mol) [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)] 2+ + H 2 + p-ncc 6 H 4 NH 2 [HNi(P Ph 2N Ph 2) 2 ] p-ncc 6 H 4 NH ± 0.2 (1S) + p-ncc 6 H 4 NH 3 H + + p-ncc 6 H 4 NH ± 0.2 (2S) H + + H - H (3S) [Ni(P Ph 2N Ph 2) 2 (CH 3 CN)] 2+ + H - [HNi(P Ph 2N Ph 2) 2 ] kcal/mol (4S) Scheme 1S From this hydride acceptor ability, the driving force for hydrogen elimination from [HNi(P Ph 2N Ph 2) 2 ] + in a 1:1 mixture of cyanoanilinium/cyanoaniline (pk a = 7.6 in acetonitrile) is 6 kcal/mol. Determination of the rate constant for H 2 production from the catalytic current. The relationship between the catalytic current i c, the catalyst concentration [cat], and the acid concentration [H + ] for a catalytic reaction that is second order in acid and first order in catalyst concentration is given by eq. 5S for acid concentrations sufficiently high that they are unchanged during the course of the reaction and at potentials sufficiently negative that electron transfer is S2

3 fast. 3-5 In eq. 5S, n is the number of electrons involved in the catalytic reaction, F is Faraday's constant, A is the area of the electrode, D is the diffusion coefficient of the catalyst, and k is the third order rate constant. i c = nfa[cat] Dk[H + ] 2 (5S) The relationship between the peak current i p, the catalyst concentration [cat], and the sweep rate ν is given by eq. 6S for a reversible, one-electron wave. In eq. 6S, R is the ideal gas constant and T is the absolute temperature. i p = FA[cat] FvD RT The ratio of i c /i p is given by eq. 7S. (6S) i c i p = n RTk[H + ] 2 Fv (7S) From eq. 7S it can be seen that ratio of ic/ip should be linear with respect to acid concentration (See Figure 5 of text). The slopes of the lines shown in Figure 5 of text should exhibit a linear dependence on (1/ν) 1/2 (see Figure S2 below) from which a rate constant of M -2 s -1 can be calculated. 18 Current (µa) y = 29.1x R 2 = [Cat] mm Figure S1. Plot of the observed catalytic current for hydrogen production versus the catalyst concentration of 6a. Conditions: 50 mv/s scan rate, 0.3 M NBu 4 BF 4 in acetonitrile, M triflic acid, glassy carbon electrode. S3

4 600 Slope of (ic/ip vs [H+]) y = x R 2 = k = 1.3x10 4 M -2 s [Scan Rate] -0.5 Figure S2. Plot of the slopes shown in Figure 5 vs 1/ν 1/2. From eq. 5 (or 7S) the slope of this plot is 0.72k 1/2, or k = 1.3x10 4 M -2 s Current (ua) ip (ma) y = 13680x R 2 = a [M] Potential versus Ferrocene (V) no complex 0.10 mm 0.19 mm 0.28 mm 0.37 mm 0.45 mm 0.54 mm 0.62 mm 0.70 mm 0.78 mm 0.85 mm 1.00 mm 1.28 mm Figure S3. Cyclic voltammograms as a function of the concentration of 6b in the presence of 0.8 atm of H 2 and M NEt 3. Conditions: 100 mv/s scan rate, 0.3 M NBu 4 BF 4 in acetonitrile, glassy carbon electrode. Inset shows plot of the catalytic current versus the concentration of 6b. S4

5 4.5 4 icat/ip y = x R 2 = (H 2 atm) 1/2 Figure S4. Plot of i c /i p for a 6.2 x10-4 M solution of 6b as a function of the square root of H 2 pressure in the presence of 7.2 x 10-3 M NEt 3. Conditions: 100 mv/s scan rate, 0.3 M NBu 4 BF 4 in acetonitrile, glassy carbon electrode. Table S1. Crystal Data for [Ni(P Ph 2N Ph 2) 2 (MeCN)](BF 4 ) 2 (6a) and [Ni(P Cy 2N Bz 2) 2 ](BF 4 ) 2 2(MeCN)(6b) (6a) (6b) formula C 58 H 59 B 2 F 8 N 5 NiP 4 C 64 H 94 B 2 F 8 N 6 NiP 4 formula weight temperature 152(2) K 152(2) K crystal system Orthorhombic Monoclinic space group P2(1)2(1)2(1) (No. 19) C2/c (No. 15) unit cell dimensions a = (5) α =90º a = (13) α =90º b = (7) β =90º b = (11)β=99.754(15)º c = (8)γ =90º c = (17) γ =90º Volume (4) Å (8) Å 3 Z 4 4 Crystal size 0.25 x 0.10 x x 0.36 x 0.10 Goodness-of-fit on F Final R indices [I 2σ(I)] R1 = , wr2 = R1 = , wr2 = R indices (all data) R1 = , wr2 = R1 = , wr2 = R = R 1 = Σ F o - F c / Σ F o Rw = [Σ[w(Fo 2 - Fc 2 ) 2 ] / Σ[w(Fo 2 ) 2 ]] 1/2 S5

6 Table S2. Atomic coordinates [x 10^4] and equivalent isotropic displacement parameters [Å 2 x 10 3 ] for C 58 H 59 B 2 F 8 N 5 NiP 4 (6a). U(eq) is defined as one third of the trace of the U ij tensor. x y z U(eq) Ni(1) 4246(1) 5224(1) 757(1) 20(1) P(1) 2702(1) 5567(1) 462(1) 22(1) P(2) 3820(1) 5897(1) 1504(1) 21(1) P(3) 5831(1) 5633(1) 664(1) 21(1) P(4) 4706(1) 4517(1) 25(1) 20(1) N(1) 4109(4) 4319(3) 1273(2) 26(1) N(2) 1707(4) 5648(3) 1514(2) 21(1) N(3) 3373(4) 6984(3) 731(3) 22(1) N(4) 5339(4) 5777(3) -512(2) 22(1) N(5) 6770(4) 4392(3) 301(2) 23(1) B(1) 1518(11) 2614(8) 1451(6) 75(4) B(2) 3355(7) 8279(5) 2854(4) 33(2) F(2) 1004(4) 2220(3) 1035(3) 79(2) F(4) 1772(5) 3298(3) 1265(3) 84(2) F(5) 2806(4) 8909(3) 2966(2) 72(2) F(6) 2695(4) 7704(3) 2750(2) 60(1) F(7) 3995(4) 8112(3) 3313(2) 55(1) F(8) 3940(4) 8384(3) 2356(2) 55(1) F(1) 610(10) 2759(6) 1793(5) 78(5) F(3) 2114(9) 2109(6) 1695(5) 70(4) F(1A) 1463(10) 2624(6) 2048(6) 73(5) F(3A) 2622(13) 2402(11) 1408(9) 142(8) C(1) 3970(5) 3922(4) 1629(3) 28(2) C(2) 3769(7) 3411(5) 2120(4) 51(2) C(3) 1677(5) 5262(4) 959(3) 26(2) C(4) 2648(5) 5546(4) 1852(3) 26(2) C(5) 2509(5) 6575(3) 462(3) 25(2) C(6) 3497(5) 6861(3) 1348(3) 22(2) C(7) 5183(5) 5000(3) -622(3) 23(2) C(8) 6157(5) 5917(4) -83(3) 25(2) C(9) 5815(5) 3958(3) 244(3) 24(2) C(10) 6788(5) 4894(3) 790(3) 24(2) C(11) 2228(5) 5317(4) -255(3) 23(2) C(12) 2715(5) 5610(4) -731(3) 27(2) C(13) 2414(6) 5404(4) -1289(3) 33(2) C(14) 1609(6) 4915(4) -1364(3) 36(2) C(15) 1131(6) 4629(4) -889(3) 34(2) C(16) 1421(5) 4820(4) -328(3) 32(2) C(17) 4686(5) 5902(4) 2122(3) 19(2) C(18) 5366(5) 5331(4) 2225(3) 20(2) C(19) 5990(5) 5314(4) 2711(3) 29(2) C(20) 5949(5) 5885(4) 3099(3) 31(2) C(21) 5264(6) 6461(4) 3014(3) 36(2) C(22) 4632(5) 6472(4) 2530(3) 28(2) C(23) 782(6) 5597(3) 1854(3) 22(2) C(24) -13(5) 5119(4) 1721(3) 32(2) C(25) -904(6) 5123(4) 2065(3) 39(2) C(26) -996(5) 5596(5) 2534(3) 43(2) C(27) -197(6) 6063(4) 2666(3) 35(2) C(28) 670(6) 6055(4) 2340(3) 33(2) C(29) 3495(5) 7729(4) 526(3) 24(2) C(30) 3638(6) 8309(4) 917(3) 33(2) S6

7 C(31) 3893(6) 8999(4) 719(4) 39(2) C(32) 3981(6) 9130(4) 137(4) 44(2) C(33) 3808(5) 8564(4) -256(3) 34(2) C(34) 3574(5) 7871(4) -60(3) 28(2) C(35) 6330(5) 6406(4) 1070(3) 23(2) C(36) 5991(5) 7108(4) 918(3) 29(2) C(37) 6407(6) 7718(4) 1189(3) 31(2) C(38) 7154(6) 7644(4) 1605(3) 34(2) C(39) 7478(6) 6940(4) 1779(3) 35(2) C(40) 7057(5) 6337(4) 1510(3) 27(2) C(41) 3816(5) 3849(3) -257(3) 20(2) C(42) 3047(5) 3555(4) 103(3) 29(2) C(43) 2364(6) 3046(3) -117(3) 30(2) C(44) 2417(6) 2827(4) -687(4) 33(2) C(45) 3162(6) 3107(4) -1035(4) 40(2) C(46) 3863(6) 3615(4) -815(3) 38(2) C(47) 5385(5) 6232(4) -1017(3) 28(2) C(48) 5345(6) 6991(4) -948(3) 37(2) C(49) 5311(6) 7426(4) -1426(3) 35(2) C(50) 5132(14) 7169(8) -1965(7) 46(4) C(51) 5107(10) 6421(6) -2047(5) 32(4) C(52) 5194(10) 5963(7) -1574(5) 28(3) C(50A) 5650(20) 7103(12) -2003(10) 34(6) C(51A) 5860(20) 6384(12) -2030(10) 47(7) C(52A) 5770(20) 5936(13) -1560(10) 39(6) C(53) 7706(5) 3998(4) 207(3) 25(2) C(54) 8445(6) 3906(4) 642(4) 40(2) C(55) 9352(7) 3516(4) 498(5) 60(3) C(56) 9506(7) 3218(5) -41(5) 57(3) C(57) 8774(7) 3307(5) -454(5) 51(2) C(58) 7861(6) 3704(4) -347(4) 35(2) Table S3. Bond lengths [Å] and angles [º] for C 58 H 59 B 2 F 8 N 5 NiP 4 (6a). Ni(1)-N(1) 2.046(6) Ni(1)-P(2) 2.187(2) Ni(1)-P(3) 2.200(2) Ni(1)-P(1) 2.207(2) Ni(1)-P(4) 2.207(2) P(1)-C(11) 1.821(7) P(1)-C(3) 1.841(7) P(1)-C(5) 1.860(6) P(2)-C(17) 1.816(7) P(2)-C(4) 1.836(7) P(2)-C(6) 1.847(6) P(3)-C(35) 1.815(7) P(3)-C(8) 1.848(7) P(3)-C(10) 1.859(6) P(4)-C(41) 1.802(7) P(4)-C(9) 1.837(6) P(4)-C(7) 1.840(6) S7

8 N(1)-C(1) 1.111(8) N(2)-C(23) 1.435(8) N(2)-C(4) 1.460(8) N(2)-C(3) 1.462(8) N(3)-C(6) 1.449(8) N(3)-C(29) 1.451(8) N(3)-C(5) 1.482(8) N(4)-C(47) 1.432(8) N(4)-C(7) 1.458(8) N(4)-C(8) 1.473(8) N(5)-C(53) 1.430(8) N(5)-C(10) 1.453(8) N(5)-C(9) 1.478(8) B(1)-F(3) 1.330(13) B(1)-F(4) 1.362(15) B(1)-F(2) 1.372(16) B(1)-F(1A) 1.377(17) B(1)-F(1) 1.442(16) B(1)-F(3A) 1.488(15) B(2)-F(6) 1.378(10) B(2)-F(5) 1.379(10) B(2)-F(7) 1.379(10) B(2)-F(8) 1.390(9) C(1)-C(2) 1.491(10) C(11)-C(12) 1.375(9) C(11)-C(16) 1.399(9) C(12)-C(13) 1.395(10) C(13)-C(14) 1.386(10) C(14)-C(15) 1.362(10) C(15)-C(16) 1.392(10) C(17)-C(18) 1.386(9) C(17)-C(22) 1.406(9) C(18)-C(19) 1.381(9) C(19)-C(20) 1.376(9) C(20)-C(21) 1.392(10) C(21)-C(22) 1.385(9) C(23)-C(24) 1.387(9) C(23)-C(28) 1.408(9) C(24)-C(25) 1.402(10) C(25)-C(26) 1.389(11) C(26)-C(27) 1.377(10) C(27)-C(28) 1.353(10) C(29)-C(34) 1.379(9) C(29)-C(30) 1.405(9) C(30)-C(31) 1.381(10) C(31)-C(32) 1.367(11) C(32)-C(33) 1.395(11) C(33)-C(34) 1.380(9) C(35)-C(40) 1.391(9) C(35)-C(36) 1.401(9) C(36)-C(37) 1.386(9) C(37)-C(38) 1.371(11) C(38)-C(39) 1.411(10) C(39)-C(40) 1.379(10) C(41)-C(46) 1.357(9) C(41)-C(42) 1.405(9) C(42)-C(43) 1.382(9) S8

9 C(43)-C(44) 1.377(10) C(44)-C(45) 1.356(11) C(45)-C(46) 1.395(10) C(47)-C(52) 1.397(13) C(47)-C(48) 1.399(9) C(47)-C(52A) 1.45(2) C(48)-C(49) 1.361(10) C(49)-C(50) 1.348(16) C(49)-C(50A) 1.52(2) C(50)-C(51) 1.380(18) C(51)-C(52) 1.378(16) C(50A)-C(51A) 1.34(3) C(51A)-C(52A) 1.36(3) C(53)-C(54) 1.397(10) C(53)-C(58) 1.399(10) C(54)-C(55) 1.415(11) C(55)-C(56) 1.370(13) C(56)-C(57) 1.354(13) C(57)-C(58) 1.412(11) N(1)-Ni(1)-P(2) 88.63(16) N(1)-Ni(1)-P(3) (17) P(2)-Ni(1)-P(3) 96.98(7) N(1)-Ni(1)-P(1) (17) P(2)-Ni(1)-P(1) 81.53(7) P(3)-Ni(1)-P(1) (7) N(1)-Ni(1)-P(4) 89.61(16) P(2)-Ni(1)-P(4) (8) P(3)-Ni(1)-P(4) 82.63(7) P(1)-Ni(1)-P(4) (7) C(11)-P(1)-C(3) 104.1(3) C(11)-P(1)-C(5) 101.7(3) C(3)-P(1)-C(5) 101.7(3) C(11)-P(1)-Ni(1) 120.9(2) C(3)-P(1)-Ni(1) 112.3(2) C(5)-P(1)-Ni(1) 113.8(2) C(17)-P(2)-C(4) 99.9(3) C(17)-P(2)-C(6) 106.8(3) C(4)-P(2)-C(6) 103.3(3) C(17)-P(2)-Ni(1) 117.7(2) C(4)-P(2)-Ni(1) 110.9(2) C(6)-P(2)-Ni(1) 116.2(2) C(35)-P(3)-C(8) 100.4(3) C(35)-P(3)-C(10) 104.3(3) C(8)-P(3)-C(10) 101.3(3) C(35)-P(3)-Ni(1) 123.3(2) C(8)-P(3)-Ni(1) 113.6(2) C(10)-P(3)-Ni(1) 111.3(2) C(41)-P(4)-C(9) 103.0(3) C(41)-P(4)-C(7) 104.4(3) C(9)-P(4)-C(7) 103.1(3) C(41)-P(4)-Ni(1) 119.9(2) C(9)-P(4)-Ni(1) 109.1(2) C(7)-P(4)-Ni(1) 115.4(2) C(1)-N(1)-Ni(1) 166.5(6) C(23)-N(2)-C(4) 113.6(5) C(23)-N(2)-C(3) 115.0(5) S9

10 C(4)-N(2)-C(3) 115.3(5) C(6)-N(3)-C(29) 116.9(5) C(6)-N(3)-C(5) 114.6(5) C(29)-N(3)-C(5) 114.9(5) C(47)-N(4)-C(7) 115.5(5) C(47)-N(4)-C(8) 114.5(5) C(7)-N(4)-C(8) 112.7(5) C(53)-N(5)-C(10) 114.9(5) C(53)-N(5)-C(9) 115.3(5) C(10)-N(5)-C(9) 114.9(5) F(3)-B(1)-F(4) 129.1(13) F(3)-B(1)-F(2) 102.3(11) F(4)-B(1)-F(2) 112.3(10) F(3)-B(1)-F(1A) 67.5(9) F(4)-B(1)-F(1A) 108.4(13) F(2)-B(1)-F(1A) 132.7(13) F(3)-B(1)-F(1) 111.8(11) F(4)-B(1)-F(1) 101.6(10) F(2)-B(1)-F(1) 94.6(11) F(1A)-B(1)-F(1) 53.8(8) F(3)-B(1)-F(3A) 44.5(9) F(4)-B(1)-F(3A) 89.2(12) F(2)-B(1)-F(3A) 106.5(12) F(1A)-B(1)-F(3A) 96.8(13) F(1)-B(1)-F(3A) 150.6(14) F(6)-B(2)-F(5) 110.4(7) F(6)-B(2)-F(7) 109.7(7) F(5)-B(2)-F(7) 110.7(7) F(6)-B(2)-F(8) 107.5(7) F(5)-B(2)-F(8) 108.8(7) F(7)-B(2)-F(8) 109.6(7) N(1)-C(1)-C(2) 178.0(8) N(2)-C(3)-P(1) 112.2(5) N(2)-C(4)-P(2) 114.6(4) N(3)-C(5)-P(1) 113.5(4) N(3)-C(6)-P(2) 111.3(4) N(4)-C(7)-P(4) 111.9(4) N(4)-C(8)-P(3) 114.3(4) N(5)-C(9)-P(4) 112.5(4) N(5)-C(10)-P(3) 109.1(4) C(12)-C(11)-C(16) 120.1(6) C(12)-C(11)-P(1) 118.2(5) C(16)-C(11)-P(1) 121.7(5) C(11)-C(12)-C(13) 120.2(6) C(14)-C(13)-C(12) 119.9(7) C(15)-C(14)-C(13) 119.5(7) C(14)-C(15)-C(16) 121.8(7) C(15)-C(16)-C(11) 118.5(7) C(18)-C(17)-C(22) 118.4(6) C(18)-C(17)-P(2) 121.6(5) C(22)-C(17)-P(2) 119.9(5) C(19)-C(18)-C(17) 121.9(6) C(20)-C(19)-C(18) 119.2(7) C(19)-C(20)-C(21) 120.5(7) C(22)-C(21)-C(20) 120.1(7) C(21)-C(22)-C(17) 119.9(7) C(24)-C(23)-C(28) 118.3(7) S10

11 C(24)-C(23)-N(2) 122.9(6) C(28)-C(23)-N(2) 118.8(6) C(23)-C(24)-C(25) 119.1(7) C(26)-C(25)-C(24) 120.9(7) C(27)-C(26)-C(25) 119.6(7) C(28)-C(27)-C(26) 119.8(7) C(27)-C(28)-C(23) 122.4(7) C(34)-C(29)-C(30) 118.3(7) C(34)-C(29)-N(3) 120.3(6) C(30)-C(29)-N(3) 121.1(6) C(31)-C(30)-C(29) 120.7(7) C(32)-C(31)-C(30) 120.3(8) C(31)-C(32)-C(33) 119.6(7) C(34)-C(33)-C(32) 120.3(7) C(29)-C(34)-C(33) 120.7(7) C(40)-C(35)-C(36) 118.6(6) C(40)-C(35)-P(3) 123.1(5) C(36)-C(35)-P(3) 118.3(5) C(37)-C(36)-C(35) 120.2(7) C(38)-C(37)-C(36) 120.7(7) C(37)-C(38)-C(39) 120.0(7) C(40)-C(39)-C(38) 118.9(7) C(39)-C(40)-C(35) 121.6(6) C(46)-C(41)-C(42) 118.1(6) C(46)-C(41)-P(4) 121.8(5) C(42)-C(41)-P(4) 120.1(5) C(43)-C(42)-C(41) 119.8(7) C(44)-C(43)-C(42) 120.9(7) C(45)-C(44)-C(43) 119.4(7) C(44)-C(45)-C(46) 120.1(8) C(41)-C(46)-C(45) 121.7(7) C(52)-C(47)-C(48) 116.6(8) C(52)-C(47)-N(4) 122.4(7) C(48)-C(47)-N(4) 118.8(6) C(52)-C(47)-C(52A) 30.6(9) C(48)-C(47)-C(52A) 118.8(11) N(4)-C(47)-C(52A) 119.9(11) C(49)-C(48)-C(47) 119.3(7) C(50)-C(49)-C(48) 123.2(9) C(50)-C(49)-C(50A) 27.0(9) C(48)-C(49)-C(50A) 118.1(10) C(49)-C(50)-C(51) 118.5(13) C(52)-C(51)-C(50) 119.5(12) C(51)-C(52)-C(47) 121.8(10) C(51A)-C(50A)-C(49) 118.6(19) C(50A)-C(51A)-C(52A) 122(2) C(51A)-C(52A)-C(47) 119(2) C(54)-C(53)-C(58) 120.6(7) C(54)-C(53)-N(5) 122.4(7) C(58)-C(53)-N(5) 117.0(6) C(53)-C(54)-C(55) 117.6(8) C(56)-C(55)-C(54) 122.3(9) C(57)-C(56)-C(55) 119.1(9) C(56)-C(57)-C(58) 121.8(9) C(53)-C(58)-C(57) 118.5(8) S11

12 Figure S5. Atom numbering scheme for [Ni(P 2 Ph N 2 Ph ) 2 (MeCN)](BF 4 ) 2 (6a) Table S4. Anisotropic displacement parameters [Å 2 x 10 3 ] for C 58 H 59 B 2 F 8 N 5 NiP 4 (6a). The anisotropic displacement factor exponent takes the form: -2 2 [h 2 a* 2 U h k a* b* U 12 ] U11 U22 U33 U23 U13 U12 Ni(1) 20(1) 19(1) 21(1) 0(1) 0(1) -1(1) P(1) 25(1) 17(1) 24(1) -1(1) -1(1) 1(1) P(2) 19(1) 20(1) 22(1) -1(1) -1(1) 0(1) P(3) 21(1) 21(1) 23(1) 0(1) 1(1) -1(1) P(4) 21(1) 17(1) 22(1) 1(1) 0(1) -1(1) N(1) 22(3) 29(3) 25(3) 1(3) 2(3) 2(3) N(2) 19(3) 26(3) 19(3) 2(3) 2(3) 2(3) N(3) 25(3) 18(3) 23(3) 4(3) -6(3) -2(2) N(4) 24(3) 17(3) 24(3) -2(2) 0(3) -2(3) N(5) 17(3) 24(3) 27(4) -6(3) 2(3) 2(3) B(1) 89(11) 82(10) 53(9) 15(7) 25(8) 27(9) B(2) 35(5) 45(6) 20(5) -1(4) 6(5) -2(5) F(2) 59(4) 72(4) 106(5) -6(4) 3(3) -5(3) F(4) 90(4) 86(4) 75(4) 39(3) -12(4) -42(4) F(5) 76(4) 52(3) 90(4) -21(3) 7(3) 22(3) F(6) 56(3) 45(3) 78(4) 3(3) -5(3) -10(3) F(7) 53(3) 70(3) 42(3) 5(3) -2(3) -2(3) F(8) 58(3) 72(3) 37(3) -1(2) 1(2) -2(3) C(1) 27(4) 24(4) 31(5) -2(3) 1(4) 8(3) C(2) 43(5) 53(6) 56(6) 24(5) 12(5) 1(5) S12

13 C(3) 20(3) 25(4) 34(4) 0(3) -2(3) 1(3) C(4) 28(4) 27(4) 22(4) 4(3) 1(3) 0(3) C(5) 26(4) 20(4) 29(4) -4(3) -13(3) 3(3) C(6) 32(4) 11(3) 21(4) -7(3) 6(3) 3(3) C(7) 27(4) 26(4) 16(4) -3(3) 2(3) -2(3) C(8) 23(4) 23(4) 30(4) 1(3) -2(3) -7(3) C(9) 24(4) 21(4) 28(4) 6(3) -2(3) 2(4) C(10) 26(4) 18(4) 30(4) -1(3) -3(4) -2(3) C(11) 26(4) 25(4) 18(4) -3(3) -3(3) 9(3) C(12) 32(4) 25(4) 23(4) -4(4) -6(4) 6(3) C(13) 39(5) 33(4) 27(5) 10(3) 6(4) 5(4) C(14) 41(5) 38(5) 28(5) -3(3) -7(4) 0(4) C(15) 36(4) 34(4) 31(5) -3(3) 1(4) -2(4) C(16) 34(4) 28(4) 33(5) 1(4) 0(4) 2(4) C(17) 13(3) 23(4) 22(4) -3(3) 5(3) -1(3) C(18) 27(4) 25(4) 8(3) -3(3) 6(3) -5(3) C(19) 22(4) 35(4) 31(4) 3(4) 3(3) 2(4) C(20) 28(4) 41(4) 24(4) -1(3) -5(4) -2(4) C(21) 55(5) 34(4) 19(4) -11(3) -7(4) -4(4) C(22) 31(4) 26(4) 26(4) -1(3) -4(4) 9(3) C(23) 25(4) 23(3) 19(4) 6(3) 1(3) 1(4) C(24) 24(4) 29(4) 43(5) -11(4) 4(4) -3(3) C(25) 23(4) 58(5) 37(5) 4(4) 8(4) -12(4) C(26) 16(4) 75(6) 39(5) 13(5) 17(4) 4(4) C(27) 33(5) 38(5) 33(5) 3(4) 3(4) 21(4) C(28) 24(4) 35(4) 41(5) -1(4) -7(4) 5(4) C(29) 18(4) 16(4) 36(5) 3(3) -5(3) 3(3) C(30) 38(5) 31(4) 30(5) -2(3) 1(4) 1(4) C(31) 41(5) 21(4) 55(6) -2(4) -6(5) -5(4) C(32) 38(5) 32(4) 62(7) 12(4) -11(5) -6(4) C(33) 28(4) 37(5) 35(5) 13(4) 4(4) -1(4) C(34) 30(4) 33(4) 20(4) 0(3) -5(3) 1(3) C(35) 18(4) 26(4) 26(4) 1(3) 1(3) -5(3) C(36) 23(4) 27(4) 36(5) 2(3) 1(3) -1(3) C(37) 31(4) 22(4) 40(5) -2(4) 9(4) -3(3) C(38) 44(5) 28(4) 31(5) -9(3) 12(4) -17(4) C(39) 31(5) 46(5) 29(5) -4(4) -8(4) -1(4) C(40) 29(4) 23(4) 28(4) 3(3) -1(4) -4(3) C(41) 19(3) 21(4) 20(4) 0(3) -1(3) -3(3) C(42) 29(4) 24(4) 34(5) -5(3) 1(4) 0(3) C(43) 25(4) 15(4) 52(6) 2(3) -3(4) -3(3) C(44) 39(5) 17(4) 44(5) 4(4) -18(4) -1(3) C(45) 48(5) 36(5) 36(5) -1(4) -7(4) -7(4) C(46) 45(5) 33(4) 37(5) -1(4) -2(4) -17(4) C(47) 28(4) 22(4) 33(5) 4(3) -1(4) -8(3) C(48) 49(5) 29(4) 32(5) 7(3) -2(4) 3(4) C(49) 45(5) 20(4) 38(5) 9(3) -10(4) -6(4) C(53) 17(4) 22(4) 35(5) 6(3) 5(3) -2(3) C(54) 38(5) 20(4) 63(6) 0(4) -16(5) 2(4) C(55) 26(5) 35(5) 118(10) 3(5) -19(6) 11(4) C(56) 34(5) 30(5) 108(9) 10(6) 20(6) 2(4) C(57) 47(6) 37(5) 68(7) 14(5) 23(5) -2(5) C(58) 34(5) 25(4) 45(5) 16(4) 11(4) 2(4) S13

14 Table S5. Hydrogen coordinates (x 10 4 ) and isotropic displacement parameters [Å 2 x 10 3 ] for C 58 H 59 B 2 F 8 N 5 NiP 4 (6a). x y z U(eq) H(2A) H(2B) H(2C) H(3A) H(3B) H(4A) H(4B) H(5A) H(5B) H(6A) H(6B) H(7A) H(7B) H(8A) H(8B) H(9A) H(9B) H(10A) H(10B) H(12) H(13) H(14) H(15) H(16) H(18) H(19) H(20) H(21) H(22) H(24) H(25) H(26) H(27) H(28) H(30) H(31) H(32) H(33) H(34) H(36) H(37) H(38) H(39) H(40) H(42) H(43) H(44) H(45) H(46) H(48) H(49) H(50) S14

15 H(51) H(52) H(50A) H(51A) H(52A) H(54) H(55) H(56) H(57) H(58) Table S6. Torsion angles [º] for C 58 H 59 B 2 F 8 N 5 NiP 4 (6a). N(1)-Ni(1)-P(1)-C(11) -98.9(3) P(2)-Ni(1)-P(1)-C(11) 175.5(3) P(3)-Ni(1)-P(1)-C(11) 84.3(3) P(4)-Ni(1)-P(1)-C(11) -5.7(3) N(1)-Ni(1)-P(1)-C(3) 24.7(3) P(2)-Ni(1)-P(1)-C(3) -60.9(3) P(3)-Ni(1)-P(1)-C(3) (3) P(4)-Ni(1)-P(1)-C(3) 117.9(3) N(1)-Ni(1)-P(1)-C(5) 139.5(3) P(2)-Ni(1)-P(1)-C(5) 54.0(3) P(3)-Ni(1)-P(1)-C(5) -37.3(3) P(4)-Ni(1)-P(1)-C(5) (3) N(1)-Ni(1)-P(2)-C(17) 64.0(3) P(3)-Ni(1)-P(2)-C(17) -50.4(2) P(1)-Ni(1)-P(2)-C(17) 173.7(2) P(4)-Ni(1)-P(2)-C(17) 29(2) N(1)-Ni(1)-P(2)-C(4) -50.0(3) P(3)-Ni(1)-P(2)-C(4) (2) P(1)-Ni(1)-P(2)-C(4) 59.7(2) P(4)-Ni(1)-P(2)-C(4) -85(2) N(1)-Ni(1)-P(2)-C(6) (3) P(3)-Ni(1)-P(2)-C(6) 78.0(3) P(1)-Ni(1)-P(2)-C(6) -57.9(3) P(4)-Ni(1)-P(2)-C(6) 158(2) N(1)-Ni(1)-P(3)-C(35) (3) P(2)-Ni(1)-P(3)-C(35) -8.6(3) P(1)-Ni(1)-P(3)-C(35) 76.4(3) P(4)-Ni(1)-P(3)-C(35) 173.5(3) N(1)-Ni(1)-P(3)-C(8) 138.3(3) P(2)-Ni(1)-P(3)-C(8) (3) P(1)-Ni(1)-P(3)-C(8) -45.0(3) P(4)-Ni(1)-P(3)-C(8) 52.1(3) N(1)-Ni(1)-P(3)-C(10) 24.7(3) P(2)-Ni(1)-P(3)-C(10) 116.4(3) P(1)-Ni(1)-P(3)-C(10) (3) P(4)-Ni(1)-P(3)-C(10) -61.5(2) N(1)-Ni(1)-P(4)-C(41) 63.2(3) P(2)-Ni(1)-P(4)-C(41) 98(2) S15

16 P(3)-Ni(1)-P(4)-C(41) 177.8(3) P(1)-Ni(1)-P(4)-C(41) -46.3(3) N(1)-Ni(1)-P(4)-C(9) -55.1(3) P(2)-Ni(1)-P(4)-C(9) -20(2) P(3)-Ni(1)-P(4)-C(9) 59.5(2) P(1)-Ni(1)-P(4)-C(9) (2) N(1)-Ni(1)-P(4)-C(7) (3) P(2)-Ni(1)-P(4)-C(7) -136(2) P(3)-Ni(1)-P(4)-C(7) -55.9(3) P(1)-Ni(1)-P(4)-C(7) 79.9(3) P(2)-Ni(1)-N(1)-C(1) 5(3) P(3)-Ni(1)-N(1)-C(1) 102(3) P(1)-Ni(1)-N(1)-C(1) -75(3) P(4)-Ni(1)-N(1)-C(1) -176(3) Ni(1)-N(1)-C(1)-C(2) 5(27) C(23)-N(2)-C(3)-P(1) 163.1(4) C(4)-N(2)-C(3)-P(1) -61.7(6) C(11)-P(1)-C(3)-N(2) (5) C(5)-P(1)-C(3)-N(2) -52.5(5) Ni(1)-P(1)-C(3)-N(2) 69.5(5) C(23)-N(2)-C(4)-P(2) (4) C(3)-N(2)-C(4)-P(2) 63.3(7) C(17)-P(2)-C(4)-N(2) 164.8(5) C(6)-P(2)-C(4)-N(2) 54.8(6) Ni(1)-P(2)-C(4)-N(2) -70.4(5) C(6)-N(3)-C(5)-P(1) -66.4(6) C(29)-N(3)-C(5)-P(1) 154.1(5) C(11)-P(1)-C(5)-N(3) (5) C(3)-P(1)-C(5)-N(3) 113.6(5) Ni(1)-P(1)-C(5)-N(3) -7.4(6) C(29)-N(3)-C(6)-P(2) (4) C(5)-N(3)-C(6)-P(2) 63.4(6) C(17)-P(2)-C(6)-N(3) 145.4(5) C(4)-P(2)-C(6)-N(3) (5) Ni(1)-P(2)-C(6)-N(3) 11.9(6) C(47)-N(4)-C(7)-P(4) (5) C(8)-N(4)-C(7)-P(4) 65.0(6) C(41)-P(4)-C(7)-N(4) 143.2(5) C(9)-P(4)-C(7)-N(4) (5) Ni(1)-P(4)-C(7)-N(4) 9.4(6) C(47)-N(4)-C(8)-P(3) 156.4(5) C(7)-N(4)-C(8)-P(3) -68.9(6) C(35)-P(3)-C(8)-N(4) (5) C(10)-P(3)-C(8)-N(4) 115.1(5) Ni(1)-P(3)-C(8)-N(4) -4.3(5) C(53)-N(5)-C(9)-P(4) (5) C(10)-N(5)-C(9)-P(4) 70.1(6) C(41)-P(4)-C(9)-N(5) 160.3(5) C(7)-P(4)-C(9)-N(5) 51.9(5) Ni(1)-P(4)-C(9)-N(5) -71.3(5) C(53)-N(5)-C(10)-P(3) 154.5(4) C(9)-N(5)-C(10)-P(3) -68.0(6) C(35)-P(3)-C(10)-N(5) (4) C(8)-P(3)-C(10)-N(5) -49.2(5) Ni(1)-P(3)-C(10)-N(5) 71.9(5) C(3)-P(1)-C(11)-C(12) 166.3(5) C(5)-P(1)-C(11)-C(12) 60.9(6) S16

17 Ni(1)-P(1)-C(11)-C(12) -66.3(6) C(3)-P(1)-C(11)-C(16) -16.3(6) C(5)-P(1)-C(11)-C(16) (6) Ni(1)-P(1)-C(11)-C(16) 111.1(5) C(16)-C(11)-C(12)-C(13) -0.9(10) P(1)-C(11)-C(12)-C(13) 176.6(5) C(11)-C(12)-C(13)-C(14) 1.3(10) C(12)-C(13)-C(14)-C(15) -1.2(10) C(13)-C(14)-C(15)-C(16) 0.7(11) C(14)-C(15)-C(16)-C(11) -0.2(11) C(12)-C(11)-C(16)-C(15) 0.3(10) P(1)-C(11)-C(16)-C(15) (5) C(4)-P(2)-C(17)-C(18) 96.9(6) C(6)-P(2)-C(17)-C(18) (5) Ni(1)-P(2)-C(17)-C(18) -23.2(6) C(4)-P(2)-C(17)-C(22) -79.2(6) C(6)-P(2)-C(17)-C(22) 28.0(6) Ni(1)-P(2)-C(17)-C(22) 160.7(5) C(22)-C(17)-C(18)-C(19) -0.5(9) P(2)-C(17)-C(18)-C(19) (5) C(17)-C(18)-C(19)-C(20) -1.1(10) C(18)-C(19)-C(20)-C(21) 2.0(10) C(19)-C(20)-C(21)-C(22) -1.4(11) C(20)-C(21)-C(22)-C(17) -0.2(11) C(18)-C(17)-C(22)-C(21) 1.2(10) P(2)-C(17)-C(22)-C(21) 177.4(5) C(4)-N(2)-C(23)-C(24) (7) C(3)-N(2)-C(23)-C(24) 10.8(9) C(4)-N(2)-C(23)-C(28) 55.5(8) C(3)-N(2)-C(23)-C(28) (6) C(28)-C(23)-C(24)-C(25) 1.6(10) N(2)-C(23)-C(24)-C(25) (6) C(23)-C(24)-C(25)-C(26) -0.2(12) C(24)-C(25)-C(26)-C(27) -0.5(12) C(25)-C(26)-C(27)-C(28) -0.4(12) C(26)-C(27)-C(28)-C(23) 1.9(11) C(24)-C(23)-C(28)-C(27) -2.6(10) N(2)-C(23)-C(28)-C(27) 176.9(6) C(6)-N(3)-C(29)-C(34) 168.3(6) C(5)-N(3)-C(29)-C(34) -53.2(8) C(6)-N(3)-C(29)-C(30) -5.3(9) C(5)-N(3)-C(29)-C(30) 133.2(7) C(34)-C(29)-C(30)-C(31) -2.6(11) N(3)-C(29)-C(30)-C(31) 171.1(6) C(29)-C(30)-C(31)-C(32) 1.8(11) C(30)-C(31)-C(32)-C(33) 0.2(12) C(31)-C(32)-C(33)-C(34) -1.6(12) C(30)-C(29)-C(34)-C(33) 1.2(11) N(3)-C(29)-C(34)-C(33) (6) C(32)-C(33)-C(34)-C(29) 0.8(11) C(8)-P(3)-C(35)-C(40) (6) C(10)-P(3)-C(35)-C(40) -18.6(7) Ni(1)-P(3)-C(35)-C(40) 109.4(6) C(8)-P(3)-C(35)-C(36) 54.6(6) C(10)-P(3)-C(35)-C(36) 159.2(5) Ni(1)-P(3)-C(35)-C(36) -72.8(6) C(40)-C(35)-C(36)-C(37) 2.5(10) S17

18 P(3)-C(35)-C(36)-C(37) (5) C(35)-C(36)-C(37)-C(38) 0.3(11) C(36)-C(37)-C(38)-C(39) -2.7(11) C(37)-C(38)-C(39)-C(40) 2.3(11) C(38)-C(39)-C(40)-C(35) 0.5(11) C(36)-C(35)-C(40)-C(39) -2.9(11) P(3)-C(35)-C(40)-C(39) 174.9(6) C(9)-P(4)-C(41)-C(46) -85.3(6) C(7)-P(4)-C(41)-C(46) 22.1(7) Ni(1)-P(4)-C(41)-C(46) 153.3(5) C(9)-P(4)-C(41)-C(42) 94.7(6) C(7)-P(4)-C(41)-C(42) (5) Ni(1)-P(4)-C(41)-C(42) -26.7(6) C(46)-C(41)-C(42)-C(43) -0.3(10) P(4)-C(41)-C(42)-C(43) 179.7(5) C(41)-C(42)-C(43)-C(44) -0.8(10) C(42)-C(43)-C(44)-C(45) 1.1(11) C(43)-C(44)-C(45)-C(46) -0.4(11) C(42)-C(41)-C(46)-C(45) 1.1(11) P(4)-C(41)-C(46)-C(45) (6) C(44)-C(45)-C(46)-C(41) -0.8(12) C(7)-N(4)-C(47)-C(52) 6.0(11) C(8)-N(4)-C(47)-C(52) 139.4(9) C(7)-N(4)-C(47)-C(48) 168.5(6) C(8)-N(4)-C(47)-C(48) -58.0(9) C(7)-N(4)-C(47)-C(52A) -29.8(15) C(8)-N(4)-C(47)-C(52A) 103.6(14) C(52)-C(47)-C(48)-C(49) -11.6(12) N(4)-C(47)-C(48)-C(49) (7) C(52A)-C(47)-C(48)-C(49) 23.0(16) C(47)-C(48)-C(49)-C(50) 12.0(15) C(47)-C(48)-C(49)-C(50A) -18.9(16) C(48)-C(49)-C(50)-C(51) -8(2) C(50A)-C(49)-C(50)-C(51) 79(3) C(49)-C(50)-C(51)-C(52) 4(2) C(50)-C(51)-C(52)-C(47) -5(2) C(48)-C(47)-C(52)-C(51) 8.5(15) N(4)-C(47)-C(52)-C(51) 171.4(9) C(52A)-C(47)-C(52)-C(51) -94(3) C(50)-C(49)-C(50A)-C(51A) -101(4) C(48)-C(49)-C(50A)-C(51A) 8(3) C(49)-C(50A)-C(51A)-C(52A) 0(4) C(50A)-C(51A)-C(52A)-C(47) 4(4) C(52)-C(47)-C(52A)-C(51A) 79(3) C(48)-C(47)-C(52A)-C(51A) -15(3) N(4)-C(47)-C(52A)-C(51A) (18) C(10)-N(5)-C(53)-C(54) 20.4(9) C(9)-N(5)-C(53)-C(54) (7) C(10)-N(5)-C(53)-C(58) (6) C(9)-N(5)-C(53)-C(58) 63.4(8) C(58)-C(53)-C(54)-C(55) 0.9(10) N(5)-C(53)-C(54)-C(55) (6) C(53)-C(54)-C(55)-C(56) -1.7(12) C(54)-C(55)-C(56)-C(57) 1.0(13) C(55)-C(56)-C(57)-C(58) 0.5(12) C(54)-C(53)-C(58)-C(57) 0.5(10) N(5)-C(53)-C(58)-C(57) (6) S18

19 C(56)-C(57)-C(58)-C(53) -1.3(11) Table S7. Atomic coordinates [x 10^4] and equivalent isotropic displacement parameters [Å 2 x 10 3 ] for C 64 H 94 B 2 F 8 N 6 NiP 4 (6b). U(eq) is defined as one third of the trace of the U ij tensor. x y z U(eq) Ni(1) (1) (1) P(1) 876(1) 2685(1) 2280(1) 22(1) P(2) 991(1) 972(1) 2655(1) 21(1) N(1) 1118(1) 1377(2) 1557(1) 23(1) N(2) 1633(2) 2287(2) 3343(1) 25(1) N(3) -1052(7) -1528(6) 3260(5) 90(4) N(3A) -757(9) -1470(9) 3039(6) 66(6) B(1) 3530(3) 666(4) 1799(2) 49(1) F(1) 3058(2) -30(2) 1688(1) 82(1) F(2) 3212(2) 1157(2) 2172(1) 86(1) F(3) 4216(3) 287(5) 2088(2) 54(2) F(3A) 4295(5) 672(9) 1978(4) 62(3) F(4) 3530(3) 1033(3) 1286(2) 141(2) C(1) 1463(2) 2157(2) 1792(1) 24(1) C(2) 1300(2) 695(2) 1975(1) 25(1) C(3) 1577(2) 2967(2) 2920(1) 27(1) C(4) 1846(2) 1505(2) 3093(1) 24(1) C(5) 570(2) 3646(2) 1881(1) 27(1) C(6) 1255(2) 4207(2) 1805(1) 33(1) C(7) 955(2) 4982(2) 1465(2) 43(1) C(8) 486(3) 4762(2) 882(2) 48(1) C(9) -192(2) 4208(3) 947(2) 46(1) C(10) 64(2) 3425(2) 1298(1) 31(1) C(11) 931(2) 7(2) 3068(1) 25(1) C(12) 765(2) 223(2) 3676(1) 30(1) C(13) 727(2) -552(2) 4044(1) 40(1) C(14) 1446(2) -1085(3) 4067(2) 44(1) C(15) 1577(2) -1314(2) 3460(2) 40(1) C(16) 1653(2) -534(2) 3098(1) 32(1) C(17) 1397(2) 1147(2) 1013(1) 30(1) C(18) 1173(2) 1797(2) 551(1) 27(1) C(19) 417(2) 1835(2) 244(1) 34(1) C(20) 205(2) 2449(2) -163(2) 41(1) C(21) 737(2) 3040(2) -271(2) 41(1) C(22) 1485(2) 3013(2) 30(1) 38(1) C(23) 1705(2) 2394(2) 436(1) 33(1) C(24) 2205(2) 2513(2) 3862(1) 33(1) C(25) 2241(2) 1890(2) 4339(1) 30(1) C(26) 1640(2) 1831(2) 4660(1) 34(1) C(27) 1669(2) 1241(3) 5094(1) 42(1) C(28) 2285(2) 703(3) 5216(2) 44(1) C(29) 2886(2) 750(2) 4903(2) 44(1) C(30) 2862(2) 1344(2) 4470(1) 37(1) C(31) -734(3) -2154(3) 3161(2) 63(1) C(32) -447(5) -2969(4) 3174(3) 104(2) S19

20 Table S8. Bond lengths [Å] and angles [º] for C 64 H 94 B 2 F 8 N 6 NiP 4 (6b). Ni(1)-P(1) (13) Ni(1)-P(1)# (13) Ni(1)-P(2)# (14) Ni(1)-P(2) (14) P(1)-C(3) 1.836(3) P(1)-C(5) 1.854(3) P(1)-C(1) 1.877(3) P(2)-C(2) 1.834(3) P(2)-C(11) 1.857(3) P(2)-C(4) 1.884(3) N(1)-C(1) 1.471(4) N(1)-C(2) 1.481(4) N(1)-C(17) 1.496(4) N(2)-C(4) 1.473(4) N(2)-C(3) 1.480(4) N(2)-C(24) 1.493(4) N(3)-C(31) 1.202(12) N(3A)-C(31) 1.146(15) B(1)-F(3A) 1.340(9) B(1)-F(4) 1.349(6) B(1)-F(2) 1.373(5) B(1)-F(1) 1.400(6) B(1)-F(3) 1.420(7) C(5)-C(6) 1.545(5) C(5)-C(10) 1.547(4) C(6)-C(7) 1.536(5) C(7)-C(8) 1.522(6) C(8)-C(9) 1.520(6) C(9)-C(10) 1.542(5) C(11)-C(16) 1.536(4) C(11)-C(12) 1.550(4) C(12)-C(13) 1.536(5) C(13)-C(14) 1.525(6) C(14)-C(15) 1.532(5) C(15)-C(16) 1.546(5) C(17)-C(18) 1.520(4) C(18)-C(19) 1.401(5) C(18)-C(23) 1.405(5) C(19)-C(20) 1.391(5) C(20)-C(21) 1.392(6) C(21)-C(22) 1.383(6) C(22)-C(23) 1.397(5) C(24)-C(25) 1.506(5) C(25)-C(30) 1.400(5) C(25)-C(26) 1.403(5) C(26)-C(27) 1.395(5) C(27)-C(28) 1.382(6) C(28)-C(29) 1.390(6) C(29)-C(30) 1.400(5) C(31)-C(32) 1.414(8) P(1)-Ni(1)-P(1)# (7) P(1)-Ni(1)-P(2)# (3) P(1)#1-Ni(1)-P(2)# (6) S20

21 P(1)-Ni(1)-P(2) 82.74(6) P(1)#1-Ni(1)-P(2) (3) P(2)#1-Ni(1)-P(2) (7) C(3)-P(1)-C(5) (15) C(3)-P(1)-C(1) (15) C(5)-P(1)-C(1) (14) C(3)-P(1)-Ni(1) (11) C(5)-P(1)-Ni(1) (11) C(1)-P(1)-Ni(1) (11) C(2)-P(2)-C(11) (15) C(2)-P(2)-C(4) (14) C(11)-P(2)-C(4) (15) C(2)-P(2)-Ni(1) (11) C(11)-P(2)-Ni(1) (11) C(4)-P(2)-Ni(1) (11) C(1)-N(1)-C(2) 111.4(2) C(1)-N(1)-C(17) 111.2(2) C(2)-N(1)-C(17) 108.6(2) C(4)-N(2)-C(3) 111.5(2) C(4)-N(2)-C(24) 111.0(2) C(3)-N(2)-C(24) 109.1(2) F(3A)-B(1)-F(4) 97.2(6) F(3A)-B(1)-F(2) 106.8(5) F(4)-B(1)-F(2) 112.3(5) F(3A)-B(1)-F(1) 126.7(8) F(4)-B(1)-F(1) 106.2(4) F(2)-B(1)-F(1) 107.2(4) F(3A)-B(1)-F(3) 29.2(4) F(4)-B(1)-F(3) 119.5(5) F(2)-B(1)-F(3) 110.4(4) F(1)-B(1)-F(3) 99.7(5) N(1)-C(1)-P(1) 112.9(2) N(1)-C(2)-P(2) 109.6(2) N(2)-C(3)-P(1) 109.0(2) N(2)-C(4)-P(2) 112.4(2) C(6)-C(5)-C(10) 112.1(2) C(6)-C(5)-P(1) 112.9(2) C(10)-C(5)-P(1) 109.2(2) C(7)-C(6)-C(5) 109.7(3) C(8)-C(7)-C(6) 111.4(3) C(9)-C(8)-C(7) 111.1(3) C(8)-C(9)-C(10) 112.4(3) C(9)-C(10)-C(5) 110.9(3) C(16)-C(11)-C(12) 111.7(2) C(16)-C(11)-P(2) 112.7(2) C(12)-C(11)-P(2) 109.3(2) C(13)-C(12)-C(11) 111.7(3) C(14)-C(13)-C(12) 111.7(3) C(13)-C(14)-C(15) 111.1(3) C(14)-C(15)-C(16) 110.9(3) C(11)-C(16)-C(15) 110.3(3) N(1)-C(17)-C(18) 111.0(3) C(19)-C(18)-C(23) 118.3(3) C(19)-C(18)-C(17) 120.6(3) C(23)-C(18)-C(17) 121.1(3) C(20)-C(19)-C(18) 120.5(3) C(19)-C(20)-C(21) 120.7(4) S21

22 C(22)-C(21)-C(20) 119.5(3) C(21)-C(22)-C(23) 120.2(3) C(22)-C(23)-C(18) 120.8(3) N(2)-C(24)-C(25) 112.6(3) C(30)-C(25)-C(26) 117.9(3) C(30)-C(25)-C(24) 121.5(3) C(26)-C(25)-C(24) 120.6(3) C(27)-C(26)-C(25) 120.3(3) C(28)-C(27)-C(26) 121.1(4) C(27)-C(28)-C(29) 119.5(4) C(28)-C(29)-C(30) 119.6(4) C(29)-C(30)-C(25) 121.5(3) N(3A)-C(31)-N(3) 39.8(7) N(3A)-C(31)-C(32) 155.4(10) N(3)-C(31)-C(32) 164.3(8) Symmetry transformations used to generate equivalent atoms: #1 -x,y,-z+0.5 Figure S6. Atom numbering scheme for [Ni(P 2 Cy N 2 Bz ) 2 ](BF 4 ) 2 2(MeCN), (6b) Table S9. Anisotropic displacement parameters [Å 2 x 10 3 ] for C 64 H 94 B 2 F 8 N 6 NiP 4 (6b). The anisotropic displacement factor exponent takes the form: -2 2 [h 2 a* 2 U h k a* b* U 12 ] U11 U22 U33 U23 U13 U12 Ni(1) 25(1) 13(1) 23(1) 0 8(1) 0 P(1) 28(1) 14(1) 24(1) -1(1) 9(1) -2(1) P(2) 27(1) 14(1) 21(1) -1(1) 5(1) 1(1) S22

23 N(1) 34(1) 15(1) 22(1) -3(1) 8(1) 3(1) N(2) 35(1) 18(2) 23(1) -4(1) 4(1) 1(1) B(1) 37(2) 66(4) 44(2) -6(2) 8(2) -4(2) F(1) 79(2) 57(2) 109(2) -11(2) 11(2) 1(2) F(2) 51(2) 96(3) 114(2) -54(2) 19(2) 8(2) F(4) 141(4) 176(5) 121(3) 88(3) 61(3) 16(3) C(1) 29(2) 19(2) 26(1) -1(1) 11(1) -1(1) C(2) 32(2) 20(2) 24(1) -4(1) 7(1) -1(1) C(3) 35(2) 17(2) 30(2) -5(1) 9(1) -3(1) C(4) 26(1) 21(2) 24(1) -6(1) 4(1) -1(1) C(5) 33(2) 20(2) 29(2) 2(1) 12(1) 2(1) C(6) 45(2) 19(2) 40(2) 3(1) 18(1) -3(2) C(7) 59(2) 21(2) 56(2) 14(2) 29(2) 1(2) C(8) 73(3) 28(2) 48(2) 17(2) 23(2) 14(2) C(9) 53(2) 47(3) 37(2) 8(2) 10(2) 15(2) C(10) 36(2) 29(2) 31(2) 3(1) 10(1) 4(2) C(11) 32(2) 18(2) 25(1) 3(1) 5(1) -1(1) C(12) 36(2) 29(2) 26(1) 2(1) 7(1) 2(1) C(13) 48(2) 40(2) 32(2) 11(2) 8(1) -6(2) C(14) 54(2) 37(2) 40(2) 19(2) 2(2) 0(2) C(15) 45(2) 25(2) 49(2) 8(2) 6(2) 3(2) C(16) 37(2) 21(2) 39(2) 3(1) 8(1) 4(1) C(17) 37(2) 27(2) 27(1) -4(1) 11(1) 2(1) C(18) 36(2) 25(2) 24(1) -4(1) 12(1) 4(1) C(19) 40(2) 34(2) 30(2) -3(1) 12(1) -2(2) C(20) 46(2) 44(2) 33(2) 2(2) 9(2) 8(2) C(21) 62(2) 29(2) 35(2) 4(2) 19(2) 9(2) C(22) 55(2) 27(2) 38(2) -6(2) 24(2) -4(2) C(23) 38(2) 36(2) 29(2) -7(1) 13(1) -3(2) C(24) 38(2) 27(2) 31(2) -7(1) 3(1) -7(2) C(25) 38(2) 26(2) 25(1) -10(1) 2(1) -5(1) C(26) 39(2) 33(2) 30(2) -8(2) 4(1) 0(2) C(27) 46(2) 51(3) 30(2) -6(2) 6(1) -8(2) C(28) 59(2) 36(2) 34(2) 1(2) -3(2) -4(2) C(29) 49(2) 36(2) 41(2) -5(2) -8(2) 2(2) C(30) 37(2) 39(2) 34(2) -11(2) 3(1) -4(2) C(31) 78(3) 41(3) 63(3) 8(2) -13(2) -18(3) C(32) 174(7) 48(3) 83(4) -16(3) -1(4) 6(4) Table S10. Hydrogen coordinates (x 10 4 ) and isotropic displacement parameters [Å 2 x 10 3 ] for C 64 H 94 B 2 F 8 N 6 NiP 4 (6b). x y z U(eq) H(1A) H(1B) H(2A) H(2B) H(3A) H(3B) H(4A) H(4B) S23

24 H(5) H(6A) H(6B) H(7A) H(7B) H(8A) H(8B) H(9A) H(9B) H(10A) H(10B) H(11) H(12A) H(12B) H(13A) H(13B) H(14A) H(14B) H(15A) H(15B) H(16A) H(16B) H(17A) H(17B) H(19) H(20) H(21) H(22) H(23) H(24A) H(24B) H(26) H(27) H(28) H(29) H(30) H(32A) H(32B) H(32C) Table S11. Torsion angles [º] for C 64 H 94 B 2 F 8 N 6 NiP 4 (6b). P(1)#1-Ni(1)-P(1)-C(3) 88.38(12) P(2)#1-Ni(1)-P(1)-C(3) (13) P(2)-Ni(1)-P(1)-C(3) (12) P(1)#1-Ni(1)-P(1)-C(5) (11) P(2)#1-Ni(1)-P(1)-C(5) 60.08(15) P(2)-Ni(1)-P(1)-C(5) (12) P(1)#1-Ni(1)-P(1)-C(1) (11) P(2)#1-Ni(1)-P(1)-C(1) (14) P(2)-Ni(1)-P(1)-C(1) 46.59(11) P(1)-Ni(1)-P(2)-C(2) (11) S24

25 P(1)#1-Ni(1)-P(2)-C(2) (13) P(2)#1-Ni(1)-P(2)-C(2) 88.06(11) P(1)-Ni(1)-P(2)-C(11) (12) P(1)#1-Ni(1)-P(2)-C(11) 62.11(15) P(2)#1-Ni(1)-P(2)-C(11) (11) P(1)-Ni(1)-P(2)-C(4) 46.47(11) P(1)#1-Ni(1)-P(2)-C(4) (14) P(2)#1-Ni(1)-P(2)-C(4) (11) C(2)-N(1)-C(1)-P(1) -81.3(3) C(17)-N(1)-C(1)-P(1) 157.4(2) C(3)-P(1)-C(1)-N(1) 132.4(2) C(5)-P(1)-C(1)-N(1) (2) Ni(1)-P(1)-C(1)-N(1) 13.0(2) C(1)-N(1)-C(2)-P(2) 55.4(3) C(17)-N(1)-C(2)-P(2) 178.3(2) C(11)-P(2)-C(2)-N(1) 161.8(2) C(4)-P(2)-C(2)-N(1) -89.7(2) Ni(1)-P(2)-C(2)-N(1) 28.7(2) C(4)-N(2)-C(3)-P(1) 56.8(3) C(24)-N(2)-C(3)-P(1) 179.7(2) C(5)-P(1)-C(3)-N(2) 160.9(2) C(1)-P(1)-C(3)-N(2) -90.5(2) Ni(1)-P(1)-C(3)-N(2) 27.7(2) C(3)-N(2)-C(4)-P(2) -81.8(3) C(24)-N(2)-C(4)-P(2) 156.3(2) C(2)-P(2)-C(4)-N(2) 131.6(2) C(11)-P(2)-C(4)-N(2) (2) Ni(1)-P(2)-C(4)-N(2) 12.6(2) C(3)-P(1)-C(5)-C(6) 47.1(2) C(1)-P(1)-C(5)-C(6) -63.1(2) Ni(1)-P(1)-C(5)-C(6) (17) C(3)-P(1)-C(5)-C(10) 172.6(2) C(1)-P(1)-C(5)-C(10) 62.3(2) Ni(1)-P(1)-C(5)-C(10) -59.1(2) C(10)-C(5)-C(6)-C(7) 55.4(4) P(1)-C(5)-C(6)-C(7) 179.3(2) C(5)-C(6)-C(7)-C(8) -57.6(4) C(6)-C(7)-C(8)-C(9) 57.8(4) C(7)-C(8)-C(9)-C(10) -55.2(4) C(8)-C(9)-C(10)-C(5) 52.6(4) C(6)-C(5)-C(10)-C(9) -53.0(4) P(1)-C(5)-C(10)-C(9) (2) C(2)-P(2)-C(11)-C(16) 48.4(3) C(4)-P(2)-C(11)-C(16) -62.3(2) Ni(1)-P(2)-C(11)-C(16) (17) C(2)-P(2)-C(11)-C(12) 173.3(2) C(4)-P(2)-C(11)-C(12) 62.6(2) Ni(1)-P(2)-C(11)-C(12) -58.9(2) C(16)-C(11)-C(12)-C(13) -53.2(4) P(2)-C(11)-C(12)-C(13) (2) C(11)-C(12)-C(13)-C(14) 53.3(4) C(12)-C(13)-C(14)-C(15) -55.8(4) C(13)-C(14)-C(15)-C(16) 57.8(4) C(12)-C(11)-C(16)-C(15) 54.9(4) P(2)-C(11)-C(16)-C(15) 178.5(2) C(14)-C(15)-C(16)-C(11) -57.3(4) C(1)-N(1)-C(17)-C(18) -61.3(3) S25

26 C(2)-N(1)-C(17)-C(18) 175.8(2) N(1)-C(17)-C(18)-C(19) -77.8(4) N(1)-C(17)-C(18)-C(23) 99.7(3) C(23)-C(18)-C(19)-C(20) 0.1(5) C(17)-C(18)-C(19)-C(20) 177.6(3) C(18)-C(19)-C(20)-C(21) -0.5(5) C(19)-C(20)-C(21)-C(22) 0.3(5) C(20)-C(21)-C(22)-C(23) 0.3(5) C(21)-C(22)-C(23)-C(18) -0.8(5) C(19)-C(18)-C(23)-C(22) 0.6(5) C(17)-C(18)-C(23)-C(22) (3) C(4)-N(2)-C(24)-C(25) -62.4(3) C(3)-N(2)-C(24)-C(25) 174.4(3) N(2)-C(24)-C(25)-C(30) 105.8(3) N(2)-C(24)-C(25)-C(26) -72.9(4) C(30)-C(25)-C(26)-C(27) -0.1(5) C(24)-C(25)-C(26)-C(27) 178.7(3) C(25)-C(26)-C(27)-C(28) -0.2(5) C(26)-C(27)-C(28)-C(29) 0.1(5) C(27)-C(28)-C(29)-C(30) 0.4(5) C(28)-C(29)-C(30)-C(25) -0.7(5) C(26)-C(25)-C(30)-C(29) 0.5(5) C(24)-C(25)-C(30)-C(29) (3) Symmetry transformations used to generate equivalent atoms: #1 -x,y,-z+1/2 Details of the theoretical calculations. All calculations on the reaction path of the model catalyst [Ni(PH 2 CH 2 NHCH 2 PH 2 ) 2 ] 2+ were carried out using the UB3LYP hybrid DFT method 6 and the all-electron 6-31G(d,p) basis 7 with the Gaussian 03 program. 8 Table S12. Cartesian coordinates (XYZ file) of the optimized model catalyst [Ni(PH 2 CH 2 NHCH 2 PH 2 ) 2 ] scf done: C P Ni P C N P C N P C H H H H H S26

27 H H H H H H H H H H H H H Tabel S13. Cartesian coordinates (XYZ file) of the optimized transition state for heterolytic cleavage of dihydrogen to form [HNi(PH 2 CH 2 N(H)HCH 2 PH 2 )(PH 2 CH 2 NHCH 2 PH 2 )] scf done: C P Ni P C N C P N C P H H H H H H H H H H H H H H H S27

28 H H H H H References and Notes 1. Edidin, R. T.; Sullivan, J. M.; Norton, J. R. J. Am. Chem. Soc. 1987, 109, (a) Wayner, D. M.; Parker, V. D. Acc. Chem. Res. 1993, 26, (b) Ellis, W. W.; Raebiger, J. W.; Curtis, C. J.; Bruno, J. W.; DuBois, D. L. J. Am. Chem. Soc. 2004, 126, Delahay, P.; Stiehl, G. L.; J. Am. Chem. Soc. 1952, 74, Nichloson, R. S.; Shain, I. Anal. Chem. 1964, 36, Saveant, J. M.; Vianello E. Electrochimica Acta 1965, 10, (e) Ibid. 1967, 12, A. D. Becke, J. Chem. Phys. 98, 5648 (1993); C. Lee, W. Yang, and R. G. Parr, Phys. Rev. B 37, 785 (1988). 7. R. Ditchfield, W. J. Hehre, and J. A. Pople, J. Chem. Phys. 54, 724 (1971). 8. Gaussian 03, Revision C.02, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and J. A. Pople, Gaussian, Inc., Pittsburgh PA, S28