SUPPORTING INFORMATION. Pyramidanes: The Covalent Form of the Ionic Compounds

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1 SUPPORTING INFORMATION Pyramidanes: The Covalent Form of the Ionic Compounds Vladimir Ya. Lee, 1 * Olga A. Gapurenko, 2 Yuki Ito, 1 Takahiko Meguro, 1 Haruka Sugasawa, 1 Akira Sekiguchi, 1 *, Ruslan M. Minyaev, 2 Vladimir I. Minkin, 2 *Rolfe H. Herber, 3 Heinz Gornitzka 4,5 1 Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki , Japan 2 Institute of Physical and Organic Chemistry, Southern Federal University, Rostov on Don, , Russian Federation 3 Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, Israel 4 CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP 44099, F Toulouse Cedex 4, France 5 Université de Toulouse, UPS, INPT, F Toulouse Cedex 4, France *To whom correspondence should be addressed. s: leevya@chem.tsukuba.ac.jp (V. Ya. L.); sekiguch@chem.tsukuba.ac.jp (A. S.); minkin@ipoc.sfedu.ru (V. I. M.). Contents of the Supporting Information: 1. Experimenal Section: details of the X-ray crystallographic analysis for pyramidanes 2, 4, 9, 10a and 10b: Figures S1 S3 (ORTEP drawings) and Tables S1 S15 (tables of the crystallographic data including atomic positional and thermal parameters). Figures S4 S25 (NMR spectral charts of the pyramidanes 2 4, 10, 14 and 15) S2 S53 2. Computational details: geometries and relative energies (Table S16), optimized geometries (Figure S26), NBO data (Table S17), resonance structures (Figure S27), NRT data (Table S18), MO diagram of E[Ge 4 H 4 ] pyramidanes 12'-16' (Figure S28), Sn[Si 4 H 4 ] molecular graph (Figure S29) S54 S61

2 1. Experimental Section: X-ray crystallography. Table S1. Crystallographic data for germapyramidane2. Identification code Empirical formula gec4_0ma C16 H36 Ge Si4 Formula weight Temperature Wavelength Crystal system Space group 150(2) K Å Orthorhombic Pnma Unit cell dimensions a = (6) Å α= 90 b = (9) Å β= 90 c = (6) Å γ= 90 Volume (2) Å 3 Z 4 Density (calculated) Mg/m 3 Absorption coefficient mm -1 F(000) 880 Crystal size 0.47 x 0.35 x 0.17 mm 3 Theta range for data collection 2.12 to Index ranges -14<=h<=11, -21<=k<=21, -13<=l<=14 Reflections collected Independent reflections 2487 [R(int) = ] Completeness to theta = ー % Absorption correction Empirical Max. and min. transmission and Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 2487 / 0 / 113 Goodness-of-fit on F Final R indices [I>2sigma(I)] R1 = , wr2 = R indices (all data) R1 = , wr2 = Largest diff. peak and hole and e.å -3 S2

3 Figure S1.Crystal structure of the germapyramidane2 (ORTEP plot with the thermal ellipsoids drawn at the 30% probability level), hydrogen atomsare not shown. S3

4 Table S2.Atomic coordinates ( x 10 4 ) and equivalent isotropic displacement parameters ( ナ 2 x 10 3 )for GeC4_0ma. U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. x y z U(eq) C(1) 2911(2) (2) 17(1) C(2) 2579(1) 6901(1) 4460(1) 17(1) C(3) 2234(2) (2) 18(1) C(4) 2585(2) 6654(1) 1304(1) 44(1) C(5) 4833(2) (2) 49(1) C(6) 3938(1) 5499(1) 3649(2) 35(1) C(7) 1332(1) 5379(1) 4001(2) 34(1) C(8) 2983(2) 5550(1) 6069(1) 35(1) C(9) 330(1) 6655(1) 6628(2) 35(1) C(10) 2156(2) (2) 53(1) Ge(1) 4056(1) (1) 20(1) Si(1) 3257(1) (1) 19(1) Si(2) 2684(1) 5841(1) 4530(1) 22(1) Si(3) 1308(1) (1) 21(1) S4

5 Table S3.Bond lengths [Å] and angles [ ] for GeC4_0ma. C(1)-C(2)# (17) C(1)-C(2) (17) C(1)-Si(1) (18) C(1)-Ge(1) (17) C(2)-C(3) (17) C(2)-Si(2) (13) C(2)-Ge(1) (13) C(3)-C(2)# (17) C(3)-Si(3) (19) C(3)-Ge(1) (18) C(4)-Si(1) (16) C(4)-H(4A) C(4)-H(4B) C(4)-H(4C) C(5)-Si(1) 1.853(3) C(5)-H(5A) C(5)-H(5B) C(5)-H(5C) C(6)-Si(2) (16) C(6)-H(6A) C(6)-H(6B) C(6)-H(6C) C(7)-Si(2) (16) C(7)-H(7A) C(7)-H(7B) C(7)-H(7C) C(8)-Si(2) (15) C(8)-H(8A) C(8)-H(8B) C(8)-H(8C) C(9)-Si(3) (16) S5

6 C(9)-H(9A) C(9)-H(9B) C(9)-H(9C) C(10)-Si(3) 1.863(2) C(10)-H(10A) C(10)-H(10B) C(10)-H(10C) Ge(1)-C(2)# (13) Si(1)-C(4)# (16) Si(3)-C(9)# (16) C(2)#1-C(1)-C(2) 90.33(14) C(2)#1-C(1)-Si(1) (7) C(2)-C(1)-Si(1) (7) C(2)#1-C(1)-Ge(1) 69.32(8) C(2)-C(1)-Ge(1) 69.32(8) Si(1)-C(1)-Ge(1) (9) C(1)-C(2)-C(3) 89.93(10) C(1)-C(2)-Si(2) (9) C(3)-C(2)-Si(2) (9) C(1)-C(2)-Ge(1) 70.07(8) C(3)-C(2)-Ge(1) 69.53(8) Si(2)-C(2)-Ge(1) (6) C(2)#1-C(3)-C(2) 89.81(14) C(2)#1-C(3)-Si(3) (7) C(2)-C(3)-Si(3) (7) C(2)#1-C(3)-Ge(1) 69.56(8) C(2)-C(3)-Ge(1) 69.56(8) Si(3)-C(3)-Ge(1) (10) Si(1)-C(4)-H(4A) Si(1)-C(4)-H(4B) H(4A)-C(4)-H(4B) Si(1)-C(4)-H(4C) S6

7 H(4A)-C(4)-H(4C) H(4B)-C(4)-H(4C) Si(1)-C(5)-H(5A) Si(1)-C(5)-H(5B) H(5A)-C(5)-H(5B) Si(1)-C(5)-H(5C) H(5A)-C(5)-H(5C) H(5B)-C(5)-H(5C) Si(2)-C(6)-H(6A) Si(2)-C(6)-H(6B) H(6A)-C(6)-H(6B) Si(2)-C(6)-H(6C) H(6A)-C(6)-H(6C) H(6B)-C(6)-H(6C) Si(2)-C(7)-H(7A) Si(2)-C(7)-H(7B) H(7A)-C(7)-H(7B) Si(2)-C(7)-H(7C) H(7A)-C(7)-H(7C) H(7B)-C(7)-H(7C) Si(2)-C(8)-H(8A) Si(2)-C(8)-H(8B) H(8A)-C(8)-H(8B) Si(2)-C(8)-H(8C) H(8A)-C(8)-H(8C) H(8B)-C(8)-H(8C) Si(3)-C(9)-H(9A) Si(3)-C(9)-H(9B) H(9A)-C(9)-H(9B) Si(3)-C(9)-H(9C) H(9A)-C(9)-H(9C) H(9B)-C(9)-H(9C) Si(3)-C(10)-H(10A) S7

8 Si(3)-C(10)-H(10B) H(10A)-C(10)-H(10B) Si(3)-C(10)-H(10C) H(10A)-C(10)-H(10C) H(10B)-C(10)-H(10C) C(2)#1-Ge(1)-C(2) 59.12(7) C(2)#1-Ge(1)-C(3) 40.91(5) C(2)-Ge(1)-C(3) 40.91(5) C(2)#1-Ge(1)-C(1) 40.61(4) C(2)-Ge(1)-C(1) 40.61(4) C(3)-Ge(1)-C(1) 58.89(7) C(5)-Si(1)-C(4) (8) C(5)-Si(1)-C(4)# (8) C(4)-Si(1)-C(4)# (12) C(5)-Si(1)-C(1) (10) C(4)-Si(1)-C(1) (6) C(4)#1-Si(1)-C(1) (6) C(8)-Si(2)-C(7) (8) C(8)-Si(2)-C(6) (8) C(7)-Si(2)-C(6) (8) C(8)-Si(2)-C(2) (6) C(7)-Si(2)-C(2) (7) C(6)-Si(2)-C(2) (7) C(10)-Si(3)-C(9) (7) C(10)-Si(3)-C(9)# (7) C(9)-Si(3)-C(9)# (10) C(10)-Si(3)-C(3) (10) C(9)-Si(3)-C(3) (6) C(9)#1-Si(3)-C(3) (6) Symmetry transformations used to generate equivalent atoms: #1 x,-y+3/2,z S8

9 Table S4. Bondanisotropic displacement parameters ( ナ 2 x 10 3 ) for GeC4_0ma. The anisotropicdisplacement factor exponent takes the form: -2π 2 [ h 2 a* 2 U h k a* b* U 12 ] U 11 U 22 U 33 U 23 U 13 U 12 C(1) 16(1) 20(1) 15(1) 0-1(1) 0 C(2) 16(1) 21(1) 15(1) 1(1) 0(1) 0(1) C(3) 16(1) 22(1) 14(1) 0 0(1) 0 C(4) 73(1) 36(1) 21(1) -3(1) -5(1) -15(1) C(5) 28(1) 92(2) 27(1) 0 12(1) 0 C(6) 36(1) 32(1) 37(1) -3(1) 5(1) 11(1) C(7) 36(1) 30(1) 37(1) -5(1) 2(1) -10(1) C(8) 47(1) 30(1) 28(1) 10(1) -2(1) 4(1) C(9) 31(1) 35(1) 40(1) 4(1) 14(1) -4(1) C(10) 29(1) 114(3) 15(1) 0 1(1) 0 Ge(1) 16(1) 27(1) 19(1) 0-2(1) 0 Si(1) 23(1) 22(1) 13(1) 0 3(1) 0 Si(2) 25(1) 18(1) 21(1) 1(1) 1(1) 1(1) Si(3) 18(1) 32(1) 14(1) 0 2(1) 0 S9

10 Table S5. Bondhydrogen coordinates ( x 10 4 ) and isotropic displacement parameters ( ナ 2 x 10 3 )for GeC4_0ma. x y z U(eq) H(4A) H(4B) H(4C) H(5A) H(5B) H(5C) H(6A) H(6B) H(6C) H(7A) H(7B) H(7C) H(8A) H(8B) H(8C) H(9A) H(9B) H(9C) H(10A) H(10B) H(10C) S10

11 Table S6. Crystallographic data for plumbapyramidane 4. Identification code Empirical formula PbC4first C16 H36 Pb Si4 Formula weight Temperature Wavelength Crystal system Space group 150(2) K Å Monoclinic Cm Unit cell dimensions a = (19) Å α= 90 b = (3) Å β= (10) c = (10) Å γ= 90 Volume (3) Å 3 Z 2 Density (calculated) Mg/m 3 Absorption coefficient mm -1 F(000) 540 Crystal size 0.38 x 0.32 x 0.25 mm 3 Theta range for data collection 2.23 to Index ranges -14<=h<=14, -21<=k<=21, -7<=l<=7 Reflections collected Independent reflections 2315 [R(int) = ] Completeness to theta = ー 99.4 % Absorption correction Empirical Max. and min. transmission and Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 2315 / 2 / 113 Goodness-of-fit on F Final R indices [I>2sigma(I)] R1 = , wr2 = R indices (all data) R1 = , wr2 = Largest diff. peak and hole and e.å -3 S11

12 Figure S2.Crystal structure of the plumbapyramidane4 (ORTEP plot with the thermal ellipsoids drawn at the 30% probability level), hydrogen atomsare not shown. S12

13 Table S7.Atomic coordinates ( x 10 4 ) and equivalent isotropic displacement parameters ( ナ 2 x 10 3 )for PbC4first. U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. x y z U(eq) Pb(1) 719(1) (1) 15(1) Si(3) -1930(2) (3) 14(1) Si(1) 3447(2) (3) 14(1) Si(2) 768(1) 1671(1) 427(2) 15(1) C(2) 763(3) 617(2) -403(7) 13(1) C(4) 4153(7) (12) 31(2) C(5) 3996(4) 888(3) 196(8) 24(1) C(10) -2482(4) 898(3) -4197(8) 22(1) C(9) -2598(7) 0-83(13) 26(2) C(3) -207(5) (9) 13(1) C(1) 1723(5) 0 230(9) 12(1) C(6) 2156(4) 1871(3) 3118(8) 25(1) C(8) -590(4) 1857(3) 1235(9) 26(1) C(7) 742(5) 2372(3) -1880(8) 28(1) S13

14 Table S8. Bond lengths [Å] and angles [ ] forpbc4first. Pb(1)-C(1) 2.440(5) Pb(1)-C(3) 2.443(6) Pb(1)-C(2) 2.453(4) Pb(1)-C(2)# (4) Si(3)-C(3) 1.867(6) Si(3)-C(9) 1.868(7) Si(3)-C(10) 1.880(4) Si(3)-C(10)# (4) Si(1)-C(4) 1.861(7) Si(1)-C(1) 1.870(6) Si(1)-C(5) 1.876(5) Si(1)-C(5)# (5) Si(2)-C(7) 1.870(5) Si(2)-C(2) 1.871(4) Si(2)-C(8) 1.872(5) Si(2)-C(6) 1.877(5) C(2)-C(1) 1.479(5) C(2)-C(3) 1.487(5) C(4)-H(4A) C(4)-H(4B) C(4)-H(4C) C(5)-H(5A) C(5)-H(5B) C(5)-H(5C) C(10)-H(10A) C(10)-H(10B) C(10)-H(10C) C(9)-H(9A) C(9)-H(9B) C(9)-H(9C) C(3)-C(2)# (5) C(1)-C(2)# (5) C(6)-H(6A) C(6)-H(6B) S14

15 C(6)-H(6C) C(8)-H(8A) C(8)-H(8B) C(8)-H(8C) C(7)-H(7A) C(7)-H(7B) C(7)-H(7C) C(1)-Pb(1)-C(3) 50.69(18) C(1)-Pb(1)-C(2) 35.18(12) C(3)-Pb(1)-C(2) 35.36(12) C(1)-Pb(1)-C(2)# (12) C(3)-Pb(1)-C(2)# (12) C(2)-Pb(1)-C(2)# (18) C(3)-Si(3)-C(9) 111.8(3) C(3)-Si(3)-C(10) (17) C(9)-Si(3)-C(10) 109.0(2) C(3)-Si(3)-C(10)# (17) C(9)-Si(3)-C(10)# (2) C(10)-Si(3)-C(10)# (3) C(4)-Si(1)-C(1) 111.2(3) C(4)-Si(1)-C(5) 108.9(2) C(1)-Si(1)-C(5) (18) C(4)-Si(1)-C(5)# (2) C(1)-Si(1)-C(5)# (18) C(5)-Si(1)-C(5)# (3) C(7)-Si(2)-C(2) (19) C(7)-Si(2)-C(8) 109.7(2) C(2)-Si(2)-C(8) 109.0(2) C(7)-Si(2)-C(6) 109.5(2) C(2)-Si(2)-C(6) 109.6(2) C(8)-Si(2)-C(6) 105.0(2) C(1)-C(2)-C(3) 89.6(3) C(1)-C(2)-Si(2) 133.4(3) C(3)-C(2)-Si(2) 132.8(3) C(1)-C(2)-Pb(1) 71.9(3) S15

16 C(3)-C(2)-Pb(1) 72.0(3) Si(2)-C(2)-Pb(1) 131.5(2) Si(1)-C(4)-H(4A) Si(1)-C(4)-H(4B) H(4A)-C(4)-H(4B) Si(1)-C(4)-H(4C) H(4A)-C(4)-H(4C) H(4B)-C(4)-H(4C) Si(1)-C(5)-H(5A) Si(1)-C(5)-H(5B) H(5A)-C(5)-H(5B) Si(1)-C(5)-H(5C) H(5A)-C(5)-H(5C) H(5B)-C(5)-H(5C) Si(3)-C(10)-H(10A) Si(3)-C(10)-H(10B) H(10A)-C(10)-H(10B) Si(3)-C(10)-H(10C) H(10A)-C(10)-H(10C) H(10B)-C(10)-H(10C) Si(3)-C(9)-H(9A) Si(3)-C(9)-H(9B) H(9A)-C(9)-H(9B) Si(3)-C(9)-H(9C) H(9A)-C(9)-H(9C) H(9B)-C(9)-H(9C) C(2)-C(3)-C(2)#1 90.0(4) C(2)-C(3)-Si(3) 135.0(2) C(2)#1-C(3)-Si(3) 135.0(2) C(2)-C(3)-Pb(1) 72.7(3) C(2)#1-C(3)-Pb(1) 72.7(3) Si(3)-C(3)-Pb(1) 113.3(2) C(2)-C(1)-C(2)#1 90.7(4) C(2)-C(1)-Si(1) 134.7(2) C(2)#1-C(1)-Si(1) 134.7(2) C(2)-C(1)-Pb(1) 72.9(3) S16

17 C(2)#1-C(1)-Pb(1) 72.9(3) Si(1)-C(1)-Pb(1) 113.3(3) Si(2)-C(6)-H(6A) Si(2)-C(6)-H(6B) H(6A)-C(6)-H(6B) Si(2)-C(6)-H(6C) H(6A)-C(6)-H(6C) H(6B)-C(6)-H(6C) Si(2)-C(8)-H(8A) Si(2)-C(8)-H(8B) H(8A)-C(8)-H(8B) Si(2)-C(8)-H(8C) H(8A)-C(8)-H(8C) H(8B)-C(8)-H(8C) Si(2)-C(7)-H(7A) Si(2)-C(7)-H(7B) H(7A)-C(7)-H(7B) Si(2)-C(7)-H(7C) H(7A)-C(7)-H(7C) H(7B)-C(7)-H(7C) Symmetry transformations used to generate equivalent atoms: #1 x,-y,z S17

18 Table S9. Bondanisotropic displacement parameters ( ナ 2 x 10 3 ) for PbC4first. The anisotropicdisplacement factor exponent takes the form: -2π 2 [ h 2 a* 2 U h k a* b* U 12 ] U 11 U 22 U 33 U 23 U 13 U 12 Pb(1) 17(1) 13(1) 15(1) 0 7(1) 0 Si(3) 11(1) 18(1) 14(1) 0 4(1) 0 Si(1) 10(1) 15(1) 17(1) 0 5(1) 0 Si(2) 21(1) 7(1) 19(1) -1(1) 10(1) 1(1) C(2) 13(2) 9(2) 15(2) 1(1) 4(1) 1(1) C(4) 17(3) 49(4) 22(3) 0 3(2) 0 C(5) 24(2) 19(2) 32(2) -4(2) 15(2) -7(2) C(10) 19(2) 23(2) 21(2) 3(2) 5(2) 7(2) C(9) 14(3) 44(4) 22(3) 0 8(3) 0 C(3) 12(2) 10(2) 15(2) 0 4(2) 0 C(1) 12(2) 6(2) 18(3) 0 4(2) 0 C(6) 27(2) 21(2) 26(2) -10(2) 11(2) -5(2) C(8) 28(2) 19(2) 34(2) 1(2) 18(2) 9(2) C(7) 45(3) 13(2) 29(2) 3(2) 19(2) 1(2) S18

19 Table S10. Bondhydrogen coordinates ( x 10 4 ) and isotropic displacement parameters ( ナ 2 x 10 3 )for PbC4first. x y z U(eq) H(4A) H(4B) H(4C) H(5A) H(5B) H(5C) H(10A) H(10B) H(10C) H(9A) H(9B) H(9C) H(6A) H(6B) H(6C) H(8A) H(8B) H(8C) H(7A) H(7B) H(7C) S19

20 Table S11. Crystallographic data for stannatetrasilapyramidane 9. Identification code Empirical formula SnSi4third_0m C36 H84 Si8 Sn Formula weight Temperature Wavelength Crystal system 150(2) K Å Triclinic Space group P-1 Unit cell dimensions a = (8) Å α= (10) b = (8) Å β= (10) c = (11) Å γ = (10) Volume (3) Å 3 Z 2 Density (calculated) Mg/m 3 Absorption coefficient mm -1 F(000) 924 Crystal size 0.23 x 0.22 x 0.16mm 3 Theta range for data collection to Index ranges -16<=h<=16, -16<=k<=16, -21<=l<=21 Reflections collected Independent reflections [R(int) = ] Completeness to theta = % Absorption correction Empirical Max. and min. transmission 0.892and0.850 Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters / 500 / 794 Goodness-of-fit on F Final R indices [I>2sigma(I)] R1 = , wr2 = R indices (all data) R1 = , wr2 = Largest diff. peak and hole and e.å -3 S20

21 Figure S3.Crystal structure of the stannatetrasilapyramidane 9 (ORTEP plot with the thermal ellipsoids drawn at the 30% probability level), hydrogen atomsare not shown andonly the main position (86%) of the rotationally disordered structure is depicted for clarity). S21

22 Table S12.Atomic coordinates ( x 10 4 ) and equivalent isotropic displacement parameters ( ナ 2 x 10 3 )for SnSi4third_0m. U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. x y z U(eq) Sn(1) 5578(1) 8073(1) 6180(1) 26(1) C(34) 9082(2) 9789(3) 8572(2) 48(1) Si(1) 6962(1) 6409(2) 7520(3) 23(1) Si(2) 5197(1) 6352(2) 7689(2) 22(1) Si(3) 4822(1) 8159(2) 7728(3) 22(1) Si(4) 6580(1) 8219(2) 7547(3) 23(1) Si(5) 8555(1) 5173(1) 7327(1) 23(1) Si(6) 4204(1) 5001(1) 7693(1) 25(1) Si(7) 3203(1) 9467(1) 7770(1) 24(1) Si(8) 7568(1) 9608(1) 7447(1) 24(1) C(1) 9691(2) 5926(3) 7136(3) 56(1) C(2) 8409(3) 4835(3) 6328(2) 32(1) C(3) 7402(3) 4422(4) 6302(2) 57(1) C(4) 9392(3) 3939(4) 6242(4) 45(1) C(5) 8328(4) 5974(3) 5543(2) 63(1) C(6) 8889(4) 3880(4) 8391(2) 42(1) C(7) 10023(6) 3116(6) 8408(5) 68(2) C(8) 8059(4) 3158(5) 8576(3) 96(2) C(9) 8936(5) 4353(5) 9099(3) 90(2) C(10) 5200(3) 3612(3) 7783(3) 51(1) C(11) 3469(4) 4622(4) 8718(2) 44(1) C(12) 3159(5) 3464(4) 8941(3) 79(2) C(13) 4157(4) 4537(5) 9462(2) 66(1) C(14) 2414(4) 5520(5) 8664(3) 83(2) C(15) 3350(3) 5519(3) 6651(2) 34(1) C(16) 2689(3) 4647(4) 6684(3) 48(1) C(17) 2590(3) 6706(3) 6455(2) 48(1) C(18) 4127(4) 5586(5) 5912(2) 62(1) C(19) 2058(2) 8766(3) 7795(3) 50(1) S22

23 C(20) 2946(3) 10848(3) 6769(2) 29(1) C(21) 1992(3) 11773(4) 6873(4) 42(1) C(22) 3926(2) 11363(2) 6537(2) 38(1) C(23) 2640(3) 10549(3) 6013(2) 46(1) C(24) 3267(3) 9663(3) 8839(2) 39(1) C(25) 4013(4) 10412(4) 8842(2) 66(1) C(26) 2114(4) 10146(4) 9072(3) 54(1) C(27) 3693(4) 8470(4) 9548(2) 71(2) C(28) 6644(2) 10895(3) 7584(3) 50(1) C(29) 8159(3) 10126(3) 6344(2) 36(1) C(30) 7197(4) 10844(3) 5685(2) 59(1) C(31) 8751(3) 9141(3) 6084(2) 46(1) C(32) 8934(5) 10894(5) 6315(4) 56(2) C(33) 8578(3) 8899(3) 8420(2) 33(1) C(35) 7949(4) 8369(6) 9205(3) 62(2) C(36) 9470(3) 7937(3) 8332(2) 49(1) Si(1') 6785(8) 6241(11) 7545(18) 28(2) Si(2') 4977(7) 6584(9) 7668(12) 23(2) Si(3') 4965(8) 8349(11) 7687(18) 27(2) Si(4') 6773(8) 8010(12) 7550(20) 31(3) Si(5') 8126(4) 4716(4) 7400(3) 27(1) Si(6') 3638(3) 5634(4) 7552(3) 26(1) Si(7') 3608(4) 9910(4) 7770(3) 32(1) Si(8') 8078(5) 9105(6) 7391(3) 39(1) C(1') 7487(15) 3494(16) 7472(18) 60(6) C(2') 8723(15) 5186(13) 6317(9) 40(4) C(3') 9125(18) 6284(15) 6104(13) 52(5) C(4') 9660(20) 4250(20) 6220(20) 51(8) C(5') 7815(18) 5470(20) 5631(12) 60(6) C(6') 9059(16) 4120(20) 8414(11) 40(6) C(7') 9690(20) 5030(20) 8422(19) 79(8) C(8') 9820(30) 3000(30) 8480(30) 57(9) C(9') 8363(18) 3920(30) 9198(11) 59(7) C(10') 2307(14) 6798(18) 7281(17) 65(5) C(11') 3392(15) 4741(15) 8683(10) 28(4) C(12') 2519(10) 4106(12) 8719(9) 19(3) S23

24 C(13') 4343(17) 3960(20) 9280(15) 58(5) C(14') 2943(16) 5800(15) 8941(12) 39(4) C(15') 3779(17) 5191(18) 6590(11) 54(5) C(16') 3010(20) 4460(20) 6535(19) 52(6) C(17') 3480(30) 6270(20) 5757(14) 76(6) C(18') 4943(18) 4590(30) 6491(18) 76(6) C(19') 4270(20) 11096(18) 7751(17) 66(5) C(20') 2649(14) 10583(17) 6787(10) 47(5) C(21') 1700(20) 11520(20) 6880(20) 56(9) C(22') 3230(20) 11150(20) 6003(13) 70(6) C(23') 2161(19) 9660(20) 6648(15) 61(5) C(24') 3086(19) 9346(19) 8888(11) 56(5) C(25') 4020(30) 8820(30) 9539(19) 85(8) C(26') 2340(30) 10380(30) 9060(30) 76(9) C(27') 2520(20) 8370(20) 8985(18) 77(6) C(28') 9438(14) 8200(20) 7255(18) 70(6) C(29') 7806(17) 10445(16) 6360(11) 49(5) C(30') 6621(18) 11160(20) 6310(20) 86(7) C(31') 7920(30) 10110(30) 5586(13) 86(9) C(32') 8620(30) 11190(30) 6300(30) 58(10) C(33') 8216(17) 9290(20) 8444(11) 47(4) C(35') 7170(20) 10140(20) 8538(17) 75(6) C(36') 8300(30) 8170(30) 9207(19) 60(7) S24

25 Table S13. Bond lengths [Å] and angles [ ] forsnsi4third_0m. Sn(1)-Si(2') 2.746(16) Sn(1)-Si(3') 2.75(2) Sn(1)-Si(4) 2.763(4) Sn(1)-Si(3) 2.782(3) Sn(1)-Si(1) 2.786(3) Sn(1)-Si(4') 2.79(3) Sn(1)-Si(1') 2.79(2) Sn(1)-Si(2) 2.801(3) C(34)-C(33') 1.46(2) C(34)-C(33) 1.534(4) Si(1)-Si(4) 2.275(2) Si(1)-Si(2) (19) Si(1)-Si(5) (15) Si(2)-Si(3) 2.279(2) Si(2)-Si(6) (14) Si(3)-Si(4) (19) Si(3)-Si(7) (15) Si(4)-Si(8) (14) Si(5)-C(1) 1.880(3) Si(5)-C(2) 1.914(3) Si(5)-C(6) 1.918(4) Si(6)-C(10) 1.891(3) Si(6)-C(11) 1.892(4) Si(6)-C(15) 1.914(3) Si(7)-C(19) 1.880(3) Si(7)-C(20) 1.912(3) Si(7)-C(24) 1.916(4) Si(8)-C(28) 1.879(3) Si(8)-C(29) 1.921(3) Si(8)-C(33) 1.922(3) C(2)-C(3) 1.509(5) S25

26 C(2)-C(4) 1.537(4) C(2)-C(5) 1.552(4) C(6)-C(8) 1.516(7) C(6)-C(9) 1.535(5) C(6)-C(7) 1.545(6) C(11)-C(13) 1.513(5) C(11)-C(12) 1.534(5) C(11)-C(14) 1.538(6) C(15)-C(17) 1.528(5) C(15)-C(16) 1.534(4) C(15)-C(18) 1.555(4) C(20)-C(22) 1.523(4) C(20)-C(21) 1.546(4) C(20)-C(23) 1.547(4) C(24)-C(25) 1.503(6) C(24)-C(27) 1.541(5) C(24)-C(26) 1.558(5) C(29)-C(31) 1.518(5) C(29)-C(32) 1.539(5) C(29)-C(30) 1.553(5) C(33)-C(36) 1.522(5) C(33)-C(35) 1.541(5) Si(1')-Si(2') 2.269(9) Si(1')-Si(4') 2.270(12) Si(1')-Si(5') 2.365(8) Si(2')-Si(3') 2.272(12) Si(2')-Si(6') 2.371(8) Si(3')-Si(4') 2.270(10) Si(3')-Si(7') 2.370(8) Si(4')-Si(8') 2.367(8) Si(5')-C(2') 1.891(13) Si(5')-C(1') 1.894(14) Si(5')-C(6') 1.922(15) S26

27 Si(6')-C(11') 1.886(14) Si(6')-C(15') 1.896(14) Si(6')-C(10') 1.925(15) Si(7')-C(19') 1.895(15) Si(7')-C(20') 1.896(14) Si(7')-C(24') 1.910(15) Si(8')-C(33') 1.897(14) Si(8')-C(29') 1.912(15) Si(8')-C(28') 1.913(15) C(2')-C(3') 1.525(16) C(2')-C(4') 1.536(16) C(2')-C(5') 1.551(17) C(6')-C(8') 1.51(2) C(6')-C(9') 1.541(17) C(6')-C(7') 1.564(18) C(11')-C(13') 1.508(17) C(11')-C(12') 1.514(15) C(11')-C(14') 1.555(17) C(15')-C(16') 1.532(17) C(15')-C(17') 1.543(18) C(15')-C(18') 1.545(18) C(20')-C(22') 1.517(17) C(20')-C(23') 1.545(18) C(20')-C(21') 1.547(16) C(24')-C(25') 1.507(19) C(24')-C(27') 1.538(18) C(24')-C(26') 1.560(17) C(29')-C(31') 1.511(18) C(29')-C(32') 1.545(16) C(29')-C(30') 1.565(18) C(33')-C(36') 1.517(19) C(33')-C(35') 1.559(18) S27

28 Si(2')-Sn(1)-Si(3') 48.8(3) Si(4)-Sn(1)-Si(3) 48.41(6) Si(4)-Sn(1)-Si(1) 48.42(6) Si(3)-Sn(1)-Si(1) 70.42(8) Si(2')-Sn(1)-Si(4') 71.0(4) Si(3')-Sn(1)-Si(4') 48.4(4) Si(2')-Sn(1)-Si(1') 48.4(3) Si(3')-Sn(1)-Si(1') 70.7(5) Si(4')-Sn(1)-Si(1') 48.0(4) Si(4)-Sn(1)-Si(2) 70.96(7) Si(3)-Sn(1)-Si(2) 48.19(6) Si(1)-Sn(1)-Si(2) 48.16(5) Si(4)-Si(1)-Si(2) 90.30(6) Si(4)-Si(1)-Si(5) (8) Si(2)-Si(1)-Si(5) (8) Si(4)-Si(1)-Sn(1) 65.25(12) Si(2)-Si(1)-Sn(1) 66.27(10) Si(5)-Si(1)-Sn(1) (16) Si(3)-Si(2)-Si(1) 89.53(6) Si(3)-Si(2)-Si(6) (8) Si(1)-Si(2)-Si(6) (8) Si(3)-Si(2)-Sn(1) 65.47(11) Si(1)-Si(2)-Sn(1) 65.57(11) Si(6)-Si(2)-Sn(1) (12) Si(4)-Si(3)-Si(2) 90.36(6) Si(4)-Si(3)-Si(7) (9) Si(2)-Si(3)-Si(7) (8) Si(4)-Si(3)-Sn(1) 65.35(12) Si(2)-Si(3)-Sn(1) 66.35(10) Si(7)-Si(3)-Sn(1) (15) Si(3)-Si(4)-Si(1) 89.80(6) Si(3)-Si(4)-Si(8) (9) Si(1)-Si(4)-Si(8) (8) S28

29 Si(3)-Si(4)-Sn(1) 66.25(12) Si(1)-Si(4)-Sn(1) 66.33(12) Si(8)-Si(4)-Sn(1) (17) C(1)-Si(5)-C(2) (16) C(1)-Si(5)-C(6) 107.7(2) C(2)-Si(5)-C(6) (17) C(1)-Si(5)-Si(1) (11) C(2)-Si(5)-Si(1) (13) C(6)-Si(5)-Si(1) (15) C(10)-Si(6)-C(11) (19) C(10)-Si(6)-C(15) (17) C(11)-Si(6)-C(15) (17) C(10)-Si(6)-Si(2) (11) C(11)-Si(6)-Si(2) (16) C(15)-Si(6)-Si(2) (13) C(19)-Si(7)-C(20) (16) C(19)-Si(7)-C(24) (17) C(20)-Si(7)-C(24) (16) C(19)-Si(7)-Si(3) (11) C(20)-Si(7)-Si(3) (13) C(24)-Si(7)-Si(3) (16) C(28)-Si(8)-C(29) (17) C(28)-Si(8)-C(33) (16) C(29)-Si(8)-C(33) (16) C(28)-Si(8)-Si(4) (11) C(29)-Si(8)-Si(4) (16) C(33)-Si(8)-Si(4) (14) C(3)-C(2)-C(4) 109.3(3) C(3)-C(2)-C(5) 107.6(3) C(4)-C(2)-C(5) 108.0(3) C(3)-C(2)-Si(5) 112.6(2) C(4)-C(2)-Si(5) 111.8(3) C(5)-C(2)-Si(5) 107.3(2) S29

30 C(8)-C(6)-C(9) 110.0(5) C(8)-C(6)-C(7) 110.0(5) C(9)-C(6)-C(7) 105.8(5) C(8)-C(6)-Si(5) 112.0(3) C(9)-C(6)-Si(5) 107.6(3) C(7)-C(6)-Si(5) 111.2(4) C(13)-C(11)-C(12) 108.0(4) C(13)-C(11)-C(14) 107.1(4) C(12)-C(11)-C(14) 106.1(4) C(13)-C(11)-Si(6) 111.2(3) C(12)-C(11)-Si(6) 111.4(3) C(14)-C(11)-Si(6) 112.7(3) C(17)-C(15)-C(16) 109.1(3) C(17)-C(15)-C(18) 108.9(3) C(16)-C(15)-C(18) 107.7(3) C(17)-C(15)-Si(6) 112.6(2) C(16)-C(15)-Si(6) 110.4(3) C(18)-C(15)-Si(6) 108.0(2) C(22)-C(20)-C(21) 108.9(3) C(22)-C(20)-C(23) 107.9(3) C(21)-C(20)-C(23) 107.7(3) C(22)-C(20)-Si(7) 113.1(2) C(21)-C(20)-Si(7) 111.0(3) C(23)-C(20)-Si(7) 108.0(2) C(25)-C(24)-C(27) 107.5(4) C(25)-C(24)-C(26) 111.2(4) C(27)-C(24)-C(26) 106.5(3) C(25)-C(24)-Si(7) 112.5(2) C(27)-C(24)-Si(7) 108.8(3) C(26)-C(24)-Si(7) 110.0(3) C(31)-C(29)-C(32) 108.6(4) C(31)-C(29)-C(30) 107.9(3) C(32)-C(29)-C(30) 109.3(3) S30

31 C(31)-C(29)-Si(8) 113.0(2) C(32)-C(29)-Si(8) 111.1(3) C(30)-C(29)-Si(8) 106.9(3) C(36)-C(33)-C(34) 109.1(3) C(36)-C(33)-C(35) 108.2(4) C(34)-C(33)-C(35) 108.5(3) C(36)-C(33)-Si(8) 112.2(2) C(34)-C(33)-Si(8) 111.5(2) C(35)-C(33)-Si(8) 107.2(3) Si(2')-Si(1')-Si(4') 90.1(3) Si(2')-Si(1')-Si(5') 135.3(4) Si(4')-Si(1')-Si(5') 134.6(4) Si(2')-Si(1')-Sn(1) 64.8(6) Si(4')-Si(1')-Sn(1) 65.9(8) Si(5')-Si(1')-Sn(1) 124.4(10) Si(1')-Si(2')-Si(3') 89.9(3) Si(1')-Si(2')-Si(6') 134.1(5) Si(3')-Si(2')-Si(6') 135.0(4) Si(1')-Si(2')-Sn(1) 66.8(7) Si(3')-Si(2')-Sn(1) 65.8(7) Si(6')-Si(2')-Sn(1) 117.3(7) Si(4')-Si(3')-Si(2') 90.0(3) Si(4')-Si(3')-Si(7') 135.4(5) Si(2')-Si(3')-Si(7') 134.6(4) Si(4')-Si(3')-Sn(1) 66.6(8) Si(2')-Si(3')-Sn(1) 65.4(6) Si(7')-Si(3')-Sn(1) 124.0(10) Si(1')-Si(4')-Si(3') 90.0(3) Si(1')-Si(4')-Si(8') 135.1(4) Si(3')-Si(4')-Si(8') 134.8(5) Si(1')-Si(4')-Sn(1) 66.0(8) Si(3')-Si(4')-Sn(1) 65.1(8) Si(8')-Si(4')-Sn(1) 123.1(11) S31

32 C(2')-Si(5')-C(1') 106.9(9) C(2')-Si(5')-C(6') 119.3(9) C(1')-Si(5')-C(6') 105.0(10) C(2')-Si(5')-Si(1') 111.1(8) C(1')-Si(5')-Si(1') 108.8(7) C(6')-Si(5')-Si(1') 105.3(9) C(11')-Si(6')-C(15') 127.8(8) C(11')-Si(6')-C(10') 99.0(10) C(15')-Si(6')-C(10') 103.1(10) C(11')-Si(6')-Si(2') 105.7(7) C(15')-Si(6')-Si(2') 112.8(7) C(10')-Si(6')-Si(2') 105.4(7) C(19')-Si(7')-C(20') 105.0(10) C(19')-Si(7')-C(24') 105.7(10) C(20')-Si(7')-C(24') 120.9(10) C(19')-Si(7')-Si(3') 108.2(8) C(20')-Si(7')-Si(3') 111.2(8) C(24')-Si(7')-Si(3') 105.2(9) C(33')-Si(8')-C(29') 118.8(10) C(33')-Si(8')-C(28') 106.0(10) C(29')-Si(8')-C(28') 104.6(10) C(33')-Si(8')-Si(4') 106.8(10) C(29')-Si(8')-Si(4') 111.8(9) C(28')-Si(8')-Si(4') 108.3(8) C(3')-C(2')-C(4') 107.4(15) C(3')-C(2')-C(5') 106.0(15) C(4')-C(2')-C(5') 109.0(17) C(3')-C(2')-Si(5') 113.4(11) C(4')-C(2')-Si(5') 113.0(14) C(5')-C(2')-Si(5') 107.7(12) C(8')-C(6')-C(9') 110(2) C(8')-C(6')-C(7') 112(2) C(9')-C(6')-C(7') 106.4(18) S32

33 C(8')-C(6')-Si(5') 110(2) C(9')-C(6')-Si(5') 108.7(12) C(7')-C(6')-Si(5') 110.6(14) C(13')-C(11')-C(12') 111.1(14) C(13')-C(11')-C(14') 108.8(16) C(12')-C(11')-C(14') 109.8(13) C(13')-C(11')-Si(6') 118.9(14) C(12')-C(11')-Si(6') 112.2(11) C(14')-C(11')-Si(6') 94.7(10) C(16')-C(15')-C(17') 102.6(17) C(16')-C(15')-C(18') 109.5(17) C(17')-C(15')-C(18') 105.1(18) C(16')-C(15')-Si(6') 114.9(14) C(17')-C(15')-Si(6') 110.3(15) C(18')-C(15')-Si(6') 113.4(14) C(22')-C(20')-C(23') 109.7(17) C(22')-C(20')-C(21') 107.7(17) C(23')-C(20')-C(21') 107.3(17) C(22')-C(20')-Si(7') 110.3(14) C(23')-C(20')-Si(7') 110.8(13) C(21')-C(20')-Si(7') 111.0(16) C(25')-C(24')-C(27') 106.2(19) C(25')-C(24')-C(26') 109(2) C(27')-C(24')-C(26') 112.6(19) C(25')-C(24')-Si(7') 109.3(17) C(27')-C(24')-Si(7') 110.8(14) C(26')-C(24')-Si(7') 108.9(17) C(31')-C(29')-C(32') 107(2) C(31')-C(29')-C(30') 106.7(19) C(32')-C(29')-C(30') 111.0(19) C(31')-C(29')-Si(8') 110.8(14) C(32')-C(29')-Si(8') 110.7(18) C(30')-C(29')-Si(8') 110.0(14) S33

34 C(34)-C(33')-C(36') 107(2) C(34)-C(33')-C(35') 104.5(18) C(36')-C(33')-C(35') 105.8(19) C(34)-C(33')-Si(8') 118.7(12) C(36')-C(33')-Si(8') 112.3(19) C(35')-C(33')-Si(8') 107.9(14) Symmetry transformations used to generate equivalent atoms: S34

35 Table S14. Bondanisotropic displacement parameters ( ナ 2 x 10 3 ) for SnSi4third_0m. The anisotropicdisplacement factor exponent takes the form: -2π 2 [ h 2 a* 2 U h k a* b* U 12 ] U 11 U 22 U 33 U 23 U 13 U 12 Sn(1) 24(1) 29(1) 26(1) -11(1) 4(1) -6(1) C(34) 45(2) 70(2) 53(2) -39(2) 7(1) -31(2) Si(1) 14(1) 21(1) 38(1) -17(1) 5(1) -2(1) Si(2) 16(1) 17(1) 37(1) -14(1) 4(1) -5(1) Si(3) 15(1) 17(1) 35(1) -14(1) 7(1) -3(1) Si(4) 16(1) 20(1) 38(1) -18(1) 5(1) -6(1) Si(5) 15(1) 23(1) 34(1) -16(1) 3(1) 0(1) Si(6) 23(1) 22(1) 35(1) -14(1) 6(1) -10(1) Si(7) 18(1) 21(1) 32(1) -12(1) 8(1) -1(1) Si(8) 20(1) 21(1) 36(1) -15(1) 4(1) -8(1) C(1) 23(1) 50(2) 113(3) -51(2) 14(2) -11(1) C(2) 35(2) 28(2) 31(1) -16(1) 6(1) 3(1) C(3) 46(2) 79(3) 67(2) -54(2) -4(2) -8(2) C(4) 45(2) 42(2) 52(2) -30(2) 11(2) 5(2) C(5) 85(3) 46(2) 33(2) -7(2) 18(2) 16(2) C(6) 41(2) 42(2) 32(2) -15(1) -4(1) 14(2) C(7) 53(3) 65(4) 60(3) -23(3) -13(3) 37(3) C(8) 86(3) 67(3) 83(3) 35(3) -2(3) -21(3) C(9) 109(4) 90(4) 48(2) -39(2) -29(2) 48(3) C(10) 35(2) 29(2) 93(3) -28(2) 15(2) -9(1) C(11) 46(3) 45(3) 33(2) 0(2) 3(2) -23(2) C(12) 107(4) 79(3) 72(3) -25(2) 37(3) -71(3) C(13) 90(3) 80(3) 29(2) -9(2) 3(2) -43(3) C(14) 75(3) 99(4) 53(2) -22(2) 32(2) 8(3) C(15) 35(2) 47(2) 34(1) -22(1) 7(1) -24(1) C(16) 47(2) 63(3) 58(2) -38(2) 6(2) -33(2) C(17) 51(2) 41(2) 43(2) -4(1) -18(1) -12(1) C(18) 67(3) 111(4) 43(2) -49(2) 24(2) -52(3) C(19) 25(1) 47(2) 90(3) -38(2) 20(2) -14(1) S35

36 C(20) 24(2) 28(1) 31(1) -11(1) 0(1) 2(1) C(21) 35(2) 29(2) 49(2) -9(2) 4(2) 9(2) C(22) 40(2) 25(1) 41(2) -7(1) 12(1) -4(1) C(23) 40(2) 53(2) 41(2) -21(1) -13(1) 6(1) C(24) 43(2) 36(2) 31(1) -14(1) 8(1) 6(1) C(25) 73(3) 97(3) 53(2) -52(2) 5(2) -27(2) C(26) 45(2) 67(3) 50(2) -35(2) 19(2) 5(2) C(27) 88(3) 60(3) 28(2) -1(2) 17(2) 22(2) C(28) 29(2) 38(2) 99(3) -44(2) 8(2) -8(1) C(29) 43(2) 33(2) 31(1) -2(1) -1(1) -21(1) C(30) 70(3) 45(2) 49(2) 8(2) -18(2) -24(2) C(31) 55(2) 62(2) 33(1) -22(2) 19(1) -29(2) C(32) 71(3) 56(3) 47(2) -7(2) 8(2) -47(3) C(33) 35(2) 43(2) 30(1) -17(1) 2(1) -21(1) C(35) 72(4) 102(4) 29(2) -22(2) 9(2) -58(3) C(36) 44(2) 42(2) 54(2) -14(2) -18(1) -3(1) Si(1') 20(4) 26(4) 41(4) -19(4) 8(4) -2(3) Si(2') 19(4) 24(4) 28(3) -15(4) -3(3) 0(3) Si(3') 22(4) 19(4) 42(4) -15(4) 10(4) -5(3) Si(4') 20(4) 32(6) 44(4) -14(6) 4(5) -11(4) Si(5') 23(2) 25(2) 34(2) -16(2) 7(2) 1(2) Si(6') 12(2) 12(2) 53(3) -13(2) -9(2) 2(2) Si(7') 29(2) 18(2) 51(3) -20(2) 3(2) 1(2) Si(8') 41(3) 53(4) 36(2) -20(2) 9(2) -34(3) C(1') 32(10) 42(10) 125(19) -52(12) 11(10) -10(8) C(2') 59(13) 14(9) 40(7) -17(7) 4(6) 14(7) C(3') 71(14) 34(9) 50(11) -18(8) 30(10) -14(9) C(4') 68(16) 34(11) 47(13) -27(12) 20(11) 10(11) C(5') 76(14) 72(17) 26(7) -16(10) 1(9) -10(11) C(6') 16(8) 46(12) 43(8) 0(9) 1(6) -7(6) C(7') 52(15) 83(16) 110(20) -34(16) -31(12) -23(12) C(8') 41(16) 52(12) 52(18) 3(11) 4(10) 4(9) C(9') 43(12) 100(20) 18(6) -18(10) -4(7) -4(11) C(10') 43(7) 53(8) 97(10) -30(7) -18(7) -3(6) C(11') 12(10) 34(11) 54(9) -33(7) 8(8) -8(6) C(12') 10(5) 10(5) 28(6) 4(4) -3(4) -4(4) S36

37 C(13') 51(8) 54(8) 68(8) -14(7) -21(7) -21(6) C(14') 44(7) 44(7) 51(7) -33(6) 12(6) -29(6) C(15') 75(13) 54(13) 54(9) -31(7) -3(11) -36(10) C(16') 62(10) 45(9) 54(10) -22(7) -13(8) -13(8) C(17') 89(10) 77(9) 67(7) -21(7) -8(8) -38(7) C(18') 77(8) 86(10) 82(10) -49(8) 16(8) -22(7) C(19') 70(10) 48(7) 95(10) -41(7) 5(7) -15(7) C(20') 29(12) 47(13) 53(9) -18(9) 5(6) 12(7) C(21') 58(16) 26(11) 49(14) 6(10) 15(11) 19(11) C(22') 56(9) 64(9) 62(7) -8(7) 9(7) 12(7) C(23') 57(9) 68(9) 61(9) -35(7) -11(6) 1(7) C(24') 48(13) 76(17) 46(8) -35(11) 16(7) 3(9) C(25') 88(11) 95(12) 62(8) -31(8) -5(8) -1(8) C(26') 76(13) 81(11) 69(12) -40(9) 25(8) -1(8) C(27') 77(10) 71(9) 75(10) -20(7) 28(7) -18(8) C(28') 39(9) 80(14) 120(20) -60(14) 25(11) -25(8) C(29') 61(12) 61(13) 43(8) -17(7) 6(10) -49(8) C(30') 76(9) 81(10) 92(11) -16(8) -12(8) -25(7) C(31') 150(30) 90(20) 38(8) -22(11) 17(15) -80(20) C(32') 76(16) 36(15) 70(19) -13(12) 2(18) -38(16) C(33') 40(12) 67(15) 42(8) -25(7) -4(9) -18(9) C(35') 65(7) 90(10) 76(9) -45(8) 8(8) -4(7) C(36') 67(12) 65(8) 54(8) -19(7) -7(8) -29(7) S37

38 Table S15. Bondhydrogen coordinates ( x 104) and isotropic displacement parameters ( ナ 2x 10 3)for SnSi4third_0m. x y z U(eq) H(34A) H(34B) H(34C) H(34D) H(34E) H(34F) H(1A) H(1B) H(1C) H(3A) H(3B) H(3C) H(4A) H(4B) H(4C) H(5A) H(5B) H(5C) H(7A) H(7B) H(7C) H(8A) H(8B) H(8C) H(9A) H(9B) H(9C) H(10A) H(10B) H(10C) H(12A) S38

39 H(12B) H(12C) H(13A) H(13B) H(13C) H(14A) H(14B) H(14C) H(16A) H(16B) H(16C) H(17A) H(17B) H(17C) H(18A) H(18B) H(18C) H(19A) H(19B) H(19C) H(21A) H(21B) H(21C) H(22A) H(22B) H(22C) H(23A) H(23B) H(23C) H(25A) H(25B) H(25C) H(26A) H(26B) H(26C) H(27A) S39

40 H(27B) H(27C) H(28A) H(28B) H(28C) H(30A) H(30B) H(30C) H(31A) H(31B) H(31C) H(32A) H(32B) H(32C) H(35A) H(35B) H(35C) H(36A) H(36B) H(36C) H(1'1) H(1'2) H(1'3) H(3'1) H(3'2) H(3'3) H(4'1) H(4'2) H(4'3) H(5'1) H(5'2) H(5'3) H(7'1) H(7'2) H(7'3) H(8'1) S40

41 H(8'2) H(8'3) H(9'1) H(9'2) H(9'3) H(10D) H(10E) H(10F) H(12D) H(12E) H(12F) H(13D) H(13E) H(13F) H(14D) H(14E) H(14F) H(16D) H(16E) H(16F) H(17D) H(17E) H(17F) H(18D) H(18E) H(18F) H(19D) H(19E) H(19F) H(21D) H(21E) H(21F) H(22D) H(22E) H(22F) H(23D) S41

42 H(23E) H(23F) H(25D) H(25E) H(25F) H(26D) H(26E) H(26F) H(27D) H(27E) H(27F) H(28D) H(28E) H(28F) H(30D) H(30E) H(30F) H(31D) H(31E) H(31F) H(32D) H(32E) H(32F) H(35D) H(35E) H(35F) H(36D) H(36E) H(36F) S42

43 Figure S4. 1 H NMR spectrum of the germapyramidane 2 in C 6 D 6. Figure S5. 13 C NMR spectrum of the germapyramidane 2 in C 6 D 6. S43

44 Figure S6. 29 Si NMR spectrum of the germapyramidane 2 in C 6 D 6. Figure S7. 1 H NMR spectrum of the stannapyramidane 3 in C 6 D 6. S44

45 Figure S8. 13 C NMR spectrum of the stannapyramidane 3 in C 6 D 6. Figure S9. 29 Si NMR spectrum of the stannapyramidane 3 in C 6 D 6. S45

46 Figure S Sn NMR spectrum of the stannapyramidane 3 in C 6 D 6. Figure S11. 1 H NMR spectrum of the plumbapyramidane 4 in C 6 D 6. S46

47 Figure S C NMR spectrum of the plumbapyramidane 4 in C 6 D 6. Figure S Si NMR spectrum of the plumbapyramidane 4 in C 6 D 6. S47

48 Figure S Pb NMR spectrum of the plumbapyramidane 4 in C 6 D 6. Figure S15. 1 H NMR spectrum of the stannatetrasilapyramidane 10 in C 6 D 6. S48

49 Figure S C NMR spectrum of the stannatetrasilapyramidane 10 in C 6 D 6. Figure S Si NMR spectrum of the stannatetrasilapyramidane 10 in C 6 D 6. S49

50 Figure S Sn NMR spectrum of the stannatetrasilapyramidane 10 in C 6 D 6. Figure S19. 1 H NMR spectrum of the pentagermapyramidane 14 in C 6 D 6. S50

51 Figure S C NMR spectrum of the pentagermapyramidane 14 in C 6 D 6. Figure S Si NMR spectrum of the pentagermapyramidane 14 in C 6 D 6. S51

52 Figure S22. 1 H NMR spectrum of the stannatetragermapyramidane 15 in C 6 D 6. Figure S C NMR spectrum of the stannatetragermapyramidane 15 in C 6 D 6. S52

53 Figure S Si NMR spectrum of the stannatetragermapyramidane 15 in C 6 D 6. Figure S Sn NMR spectrum of the stannatetragermapyramidane 15 in C 6 D 6. S53

54 2. Computations. Table S16. Calculation data (B3LYP/Def2TZVP): number of imaginary frequencies (λ), relative energies with zero-point correction ( E ZPE, kcal mol -1 ), pyramidal (E E') and basal (E' E') bond lengths (Å), buckling distances a (BD, Å), folding angles (FA) of pyramidanes and corresponding distorted structures. Structure Pyramidane (C 4v or C 4 ) Distorted structure (C 2v or C 2 ) λ E ZPE E E' E' E' λ E ZPE BD FA E E' E' E' 5' C[C 4 H 4 ] " C[C 4 (SiH 3 ) 4 ] C[C 4 (SiMe 3 ) 4 ] / ' Si[C 4 H 4 ] " Si[C 4 (SiH 3 ) 4 ] Si[C 4 (SiMe 3 ) 4 ] / / ' Ge[C 4 H 4 ] " Ge[C 4 (SiH 3 ) 4 ] Ge[C 4 (SiMe 3 ) 4 ] ' Sn[C 4 H 4 ] " Sn[C 4 (SiH 3 ) 4 ] Sn[C 4 (SiMe 3 ) 4 ] ' Pb[C 4 H 4 ] " Pb[C 4 (SiH 3 ) 4 ] Pb[C 4 (SiMe 3 ) 4 ] / ' C[Si 4 H 4 ] / " C[Si 4 (SiH 3 ) 4 ] / "' C[Si 4 (SiMe 3 ) 4 ] / / / C[Si 4 (SiMe t Bu 2 ) 4 ] / / ' Si[Si 4 H 4 ] / " Si[Si 4 (SiH 3 ) 4 ] / "' Si[Si 4 (SiMe 3 ) 4 ] / / Si[Si 4 (SiMe t Bu 2 ) 4 ] ' Ge[Si 4 H 4 ] / " Ge[Si 4 (SiH 3 ) 4 ] / "' Ge[Si 4 (SiMe 3 ) 4 ] / / Ge[Si 4 (SiMe t Bu 2 ) 4 ] ' Sn[Si 4 H 4 ] / " Sn[Si 4 (SiH 3 ) 4 ] / "' Sn[Si 4 (SiMe 3 ) 4 ] Sn[Si 4 (SiMe t Bu 2 ) 4 ] ' Pb[Si 4 H 4 ] / " Pb[Si 4 (SiH 3 ) 4 ] / "' Pb[Si 4 (SiMe 3 ) 4 ] Pb[Si 4 (SiMe t Bu 2 ) 4 ] / / S54

55 12' C[Ge 4 H 4 ] / " C[Ge 4 (SiH 3 ) 4 ] / "' C[Ge 4 (SiMe 3 ) 4 ] / / / C[Ge 4 (SiMe t Bu 2 ) 4 ] / / / ' Si[Ge 4 H 4 ] / " Si[Ge 4 (SiH 3 ) 4 ] / "' Si[Ge 4 (SiMe 3 ) 4 ] / / / Si[Ge 4 (SiMe t Bu 2 ) 4 ] / ' Ge[Ge 4 H 4 ] / " Ge[Ge 4 (SiH 3 ) 4 ] / "' Ge[Ge 4 (SiMe 3 ) 4 ] / / / Ge[Ge 4 (SiMe t Bu 2 ) 4 ] / / / ' Sn[Ge 4 H 4 ] / " Sn[Ge 4 (SiH 3 ) 4 ] / "' Sn[Ge 4 (SiMe 3 ) 4 ] / / / Sn[Ge 4 (SiMe t Bu 2 ) 4 ] / / ' Pb[Ge 4 H 4 ] / " Pb[Ge 4 (SiH 3 ) 4 ] / "' Pb[Ge 4 (SiMe 3 ) 4 ] / / / Pb[Ge 4 (SiMe t Bu 2 ) 4 ] / / / a distance between the centers of two diagonals of the distorted E' 4 -base. S55

56 Figure S26. Optimized geometries of the selected pyramidanes: bond lengths are in Å, hydrogen atoms are not shown. S56

57 Table S17. NBO data (B3LYP/Def2TZVP). Structure Natural charge Wiberg bond index Polarization coefficients on atoms in pyramidal bonds Apical Basal atom Pyramidal Basal Apical Basal atom atom bond bond atom 5' C[C 4 H 4 ] C[C 4 (SiMe 3 ) 4 ] / / C[C 4 (SiMe 3 ) 4 ] (C 2v ) / / / ' Si[C 4 H 4 ] / / Si[C 4 (SiMe 3 ) 4 ] a 6 Si[C 4 (SiMe 3 ) 4 ] (C 2v ) / / ' Ge[C 4 H 4 ] / / Ge[C 4 (SiMe 3 ) 4 ] ' Sn[C 4 H 4 ] / / Sn[C 4 (SiMe 3 ) 4 ] / / ' Pb[C 4 H 4 ] Pb[C 4 (SiMe 3 ) 4 ] / / Pb[C 4 (SiMe 3 ) 4 ] (C 2v ) ' C[Si 4 H 4 ] ' C[Si 4 H 4 ] (C 2v ) / / / / C[Si 4 (SiMe t Bu 2 ) 4 ] / / C[Si 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / ' Si[Si 4 H 4 ] / / ' Si[Si 4 H 4 ] (C 2v ) / / / / Si[Si 4 (SiMe t Bu 2 ) 4 ] / / ' Ge[Si 4 H 4 ] / / ' Ge[Si 4 H 4 ] (C 2v ) / / / / Ge[Si 4 (SiMe t Bu 2 ) 4 ] / / ' Sn[Si 4 H 4 ] / / ' Sn[Si 4 H 4 ] (C 2v ) / / / / Sn[Si 4 (SiMe t Bu 2 ) 4 ] / / ' Pb[Si 4 H 4 ] / / ' Pb[Si 4 H 4 ] (C 2v ) / / / / Pb[Si 4 (SiMe t Bu 2 ) 4 ] / / Pb[Si 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / ' C[Ge 4 H 4 ] / / ' C[Ge 4 H 4 ] (C 2v ) / / / / C[Ge 4 (SiMe t Bu 2 ) 4 ] / / C[Ge 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / ' Si[Ge 4 H 4 ] / / ' Si[Ge 4 H 4 ] (C 2v ) / / / / Si[Ge 4 (SiMe t Bu 2 ) 4 ] / / Si[Ge 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / ' Ge[Ge 4 H 4 ] / / ' Ge[Ge 4 H 4 ] (C 2v ) / / / / Ge[Ge 4 (SiMe t Bu 2 ) 4 ] / / Ge[Ge 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / 0.83 S57

58 15' Sn[Ge 4 H 4 ] / / ' Sn[Ge 4 H 4 ] (C 2v ) / / / / Sn[Ge 4 (SiMe t Bu 2 ) 4 ] / / Sn[Ge 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / ' Pb[Ge 4 H 4 ] / / ' Pb[Ge 4 H 4 ] (C 2v ) / / / / Pb[Ge 4 (SiMe t Bu 2 ) 4 ] / / Pb[Ge 4 (SiMe t Bu 2 ) 4 ] (C 2v ) / / / / 0.87 a no natural orbital corresponding to this bond S58

59 E E E E H H H H H H H H H H H H H H H H E[C 4 H 4 ] 5 : E = C : E = Si : E = Ge : E = Sn E[Si 4 H 4 ] 8 : E = Si : E = Ge : E = Sn E[Ge 4 H 4 ] 12 : E = C : E = Si : E = Ge : E = Sn Pb H H H H 4 : C C C C C H Si Si Si Si H H H H Si Si Si Si H H H H Si Si Si Si H H H H Si Si H H H H Si Si Si Si H H H 7 : Figure 27. Resonance structures and their NRT weights (%). S59

60 Table S18. NRT bond orders and bond ionic characters in model pyramidanes (B3LYP/Def2TZVP ). Structure Pyramidal bond Basal bond b EE' % ionic b E'E' % ionic 5' C[C 4 H 4 ] ' Si[C 4 H 4 ] ' Ge[C 4 H 4 ] ' Sn[C 4 H 4 ] ' Pb[C 4 H 4 ] / /8.3 7' C[Si 4 H 4 ] /0.8196/ 38.5/60.7/ / / ' Si[Si 4 H 4 ] ' Ge[Si 4 H 4 ] ' Sn[Si 4 H 4 ] ' Pb[Si 4 H 4 ] a 12' C[Ge 4 H 4 ] ' Si[Ge 4 H 4 ] ' Ge[Ge 4 H 4 ] ' Sn[Ge 4 H 4 ] ' Pb[Ge 4 H 4 ] a Basic NRT calculations did not give any resonance structure for Pb[E 4 H 4 ] (E = Si, Ge) pyramidanes. S60

61 Figure S28. Comparison of the cage bonding MO of the model H-substituted Ge-based pyramidanes E[Ge 4 H 4 ] (12 : E = C; 13 : E = Si; 14 : E = Ge; 15 : E = Sn; 16 : E = Pb). Figure S29. Molecular graph of the model stannasilapyramidane Sn[Si 4 H 4 ]: bond critical points are shown in purple, ring critical points in yellow, cage critical point in blue. S61