Copyright Wiley−VCH Verlag GmbH, 69451 Weinheim, 2002

Chem. Eur. J. 2002

Suppor ting Information

for

" Valence Charge Concentrations and Electron Delocalization in

L ithium Alkyls: Negative Hyperconjugation and Agostic Bonding"

Wolfgang Scherer,* Peter Sirsch, Dmitry Shorokhov, G. Sean McGrady,

Sax A. Mason, and Michael G. Gardiner

Contents:

S1 − Topological analysis and geometrical parameters

S2 − Fractional atomic coordinates and mean−square atomic displacement parameters

S3 − Kappa and multipole parameters

S4 − Local coordinate systems

S5 − Model deformation and residual density maps after multipole refinement

S6 − Comparison of multipole models with different flexibility

S7 − Geometrical and topological parameters of the calculated model systems

1, 2, 3, 4, 5, 10 and 11

S8 − Geometrical and topological parameters of the calculated model systems

6, 6a, 7 and 9

S9 − Ellipticity angle along the C1−Si2 bondpath of 8

S1: Topological analysis and geometr ical parameters of [{2−(Me3Si)2C(Li)C5H4N}2] 8.

Unit Methoda Distance [Å] ρ(r c) [e/Å3] ∇2ρ(r c) [e/Å5] Ellipticity ε

Li···N_a Experiment 1.9508 0.215(2) 5.201(2) 0.02

Theory I 1.9636 0.24 5.07 0.05

Theory II 0.24 4.76 0.04

Li−C1 Experiment 2.2049 0.150(2) 2.521(1) 0.12

Theory I 2.1757 0.19 2.76 0.10

Theory II 0.19 2.52 0.11

C1−Si2 Experiment 1.8592(4) 0.859(14) 1.73(3) 0.13

Theory I 1.8819 0.79 4.72 0.11

Theory II 0.80 3.16 0.11

C1−Si1 Experiment 1.8552(4) 0.756(15) 4.25(3) 0.19

Theory I 1.8798 0.77 4.69 0.12

Theory II 0.78 3.16 0.12

C1−C11 Experiment 1.4798(5) 1.78(2) −11.29(5) 0.12

Theory I 1.4783 1.73 −13.60 0.12

Theory II 1.73 −13.38 0.11

Si1−C2 Experiment 1.8804(6) 0.693(17) 4.63(3) 0.22

Theory I 1.9050 0.78 4.54 0.01

Theory II 0.79 2.92 0.01

Si1−C3 Experiment 1.8930(8) 0.758(14) 2.73(3) 0.20

Theory I 1.9197 0.75 4.50 0.01

Theory II 0.76 2.99 0.01

Si1−C4 Experiment 1.8781(7) 0.765(16) 4.23(3) 0.14

Theory I 1.9023 0.78 4.65 0.01

Theory II 0.79 3.01 0.01

Si2−C5 Experiment 1.8888(6) 0.735(16) 4.41(3) 0.07

Theory 1.9094 0.77 4.46 0.01

Theory II 0.78 2.89 0.02

Si2−C6 Experiment 1.8811(5) 0.714(16) 5.39(3) 0.12

Theory 1.9083 0.77 4.52 0.01

Theory II 0.78 2.91 0.01a The experimental values were obtained by multipole refinement of the experimental charge density, the theoretical

calculations were performed at the B3LYP/6−311G(d,p)//B3LYP/6−31G(d) (I) and the B3LYP/6–311G(3d,3p)//

B3LYP/6−31G(d) (II) level of theory, respectively.

Unit Methoda Distance [Å] ρ(r c) [e/Å3] ∇2ρ(r c) [e/Å5] Ellipticity ε

Si2−C7 Experiment 1.8947(7) 0.717(16) 3.84(3) 0.03

Theory I 1.9180 0.75 4.50 0.01

Theory II 0.76 2.97 0.01

N−C11 Experiment 1.3636(6) 2.17(3) −17.34(13) 0.23

Theory I 1.3729 2.13 −21.91 0.09

Theory II 2.16 −22.96 0.10

C11−C12 Experiment 1.4168(6) 2.06(2) −16.48(5) 0.21

Theory I 1.4223 2.00 −19.18 0.19

Theory II 2.01 −18.88 0.18

C12−C13 Experiment 1.3834(7) 2.165(19) −19.03(4) 0.23

Theory I 1.3846 2.12 −21.28 0.22

Theory II 2.13 −21.06 0.21

C13−C14 Experiment 1.3948(7) 2.133(19) −18.090(0) 0.24

Theory I 1.4000 2.06 −20.43 0.18

Theory II 2.07 −20.04 0.17

C14−C15 Experiment 1.3821(7) 2.20(3) −20.68(6) 0.24

Theory I 1.3858 2.13 −21.47 0.24

Theory II 2.13 −21.20 0.23

N−C15 Experiment 1.3454(7) 2.39(3) −22.34(12) 0.22

Theory I 1.3450 2.24 −22.76 0.11

Theory II 2.27 −24.80 0.13

C7−H7c Experiment 1.0981 1.71(4) −12.85(11) 0.08

Theory I 1.1009 1.76 −19.68 0.03

Theory II 1.78 −20.03 0.03

C3−H3b Experiment 1.1003 1.73(5) −13.01(17) 0.05

Theory I 1.0987 1.78 −20.08 0.02

Theory II 1.80 −20.48 0.02

C3−H3c Experiment 1.0919 1.65(4) −12.64(11) 0.08

Theory I 1.1001 1.78 −19.89 0.02

Theory II 1.79 −20.25 0.03

C3−Li_a Experiment 2.5107 0.082(1) 0.828(1) 0.69

Theory I 2.4793 0.06 1.30 1.16

Theory II 0.06 1.30 0.98a The experimental values were obtained by multipole refinement of the experimental charge density, the theoretical

calculations were performed at the B3LYP/6−311G(d,p)//B3LYP/6−31G(d) (I) and the B3LYP/6–311G(3d,3p)//

B3LYP/6−31G(d) (II) level of theory, respectively.

Selected angles [deg] for [{2−(Me3Si)2C(Li)C5H4N}2] 8.a

C1−Li−N_a Experiment 145.90 Li_a−N−C11 Experiment 104.12

Theory 142.9 Theory 110.4

Li_a−Li−C1 Experiment 65.55 Li−C1−Si1 Experiment 104.51

Theory 70.6 Theory 105.1

Li−Li_a−N Experiment 104.46 Li−C1−Si2 Experiment 88.92

Theory 95.7 Theory 90.6

Li_a−N−C15 Experiment 135.39 Li−C1−C11 Experiment 123.15

Theory 128.6 Theory 116.5a The experimental values were obtained by multipole refinement of the experimental charge density, the theoretical

calculations were performed at the B3LYP/6−31G(d) level of theory.

S2a: Fractional atomic coordinates and mean−square atomic displacement parameters for

the non−hydrogen atoms of 8.

Fractional atomic coordinates

Atom x/a y/b z/c

Si(2) 0.302283(9) 0.263099(13) −0.086250(9)

Si(1) 0.360087(10) 0.364467(12) 0.142651(9)

N 0.32170(4) 0.65175(5) 0.01422(4)

C(1) 0.34445(3) 0.40747(4) 0.00109(3)

C(2) 0.21836(5) 0.35769(7) 0.20396(4)

C(3) 0.44800(8) 0.49177(8) 0.22359(5)

C(4) 0.43410(5) 0.19839(7) 0.16947(5)

C(5) 0.25199(5) 0.31911(7) −0.22208(4)

C(6) 0.18768(5) 0.14550(5) −0.04195(5)

C(7) 0.43079(6) 0.15207(8) −0.10675(7)

C(11) 0.27294(3) 0.53035(4) −0.01261(3)

C(12) 0.15600(4) 0.52954(5) −0.04788(4)

C(13) 0.09272(4) 0.64778(5) −0.05310(4)

C(14) 0.14460(4) 0.77001(5) −0.02328(4)

C(15) 0.25923(4) 0.76603(5) 0.00900(3)

Li 0.519190 0.392970 −0.052800

Mean−square atomic displacement parameters [Å2]Atom U11 U22 U33 U12 U13 U23

Si(2) 0.01521(4) 0.01959(5) 0.02321(5) −0.00064(3) −0.00003(3) −0.00526(4)

Si(1) 0.01713(4) 0.02092(5) 0.01712(4) 0.00037(4) −0.00047(3) 0.00369(4)

N 0.01575(14) 0.01575(16) 0.02033(15) 0.00046(12) −0.00024(12) −0.00178(13)

C(1) 0.01391(12) 0.01611(14) 0.01614(13) 0.00126(11) 0.00004(10) −0.00010(11)

C(2) 0.0262(2) 0.0590(4) 0.02440(18) 0.0003(2) 0.00801(16) 0.0090(2)

C(3) 0.0428(3) 0.0346(3) 0.01996(19) −0.0082(3) −0.0073(2) −0.0005(2)

C(4) 0.0370(3) 0.0277(2) 0.0389(3) 0.0071(2) −0.0079(2) 0.01062(19)

C(5) 0.0315(2) 0.0485(3) 0.02199(18) −0.0046(2) −0.00559(16) −0.00591(19)

C(6) 0.02615(19) 0.02222(18) 0.0453(3) −0.00720(16) 0.00334(18) −0.00462(17)

C(7) 0.0243(2) 0.0278(3) 0.0458(3) 0.0046(2) 0.0023(2) −0.0152(3)

C(11) 0.01226(12) 0.01619(14) 0.01658(13) 0.00037(11) 0.00075(10) 0.00121(11)

C(12) 0.01265(12) 0.01972(16) 0.0349(2) 0.00008(11) −0.00214(12) 0.00216(13)

C(13) 0.01447(13) 0.02391(19) 0.0407(2) 0.00346(13) −0.00146(14) 0.00497(16)

C(14) 0.01988(16) 0.01992(17) 0.03251(19) 0.00554(13) 0.00302(13) 0.00352(14)

C(15) 0.02103(16) 0.01679(16) 0.02521(17) 0.00222(14) 0.00148(12) −0.00099(12)

Li 0.015314 0.040846 0.029042 0.002015 0.001001 −0.001989

S2b: Fractional atomic coordinates and mean−square atomic displacement parameters for

the hydrogen atoms of 8.

Fractional atomic coordinates

Atom x/a y/b z/c

H(2a) 0.229000 0.335210 0.287310

H(2b) 0.163710 0.278590 0.168450

H(2c) 0.171690 0.452050 0.194260

H(3a) 0.450260 0.461780 0.306060

H(3b) 0.411360 0.594320 0.220820

H(3c) 0.536830 0.498040 0.202810

H(4a) 0.442330 0.182190 0.254950

H(4b) 0.520350 0.197010 0.141910

H(4c) 0.388230 0.111860 0.135300

H(5a) 0.239740 0.230740 −0.272890

H(5b) 0.311180 0.383330 −0.258120

H(5c) 0.170370 0.370720 −0.226310

H(6a) 0.173660 0.063050 −0.099050

H(6b) 0.106420 0.196770 −0.036710

H(6c) 0.210030 0.099030 0.034400

H(7a) 0.402480 0.062230 −0.150680

H(7b) 0.475150 0.117940 −0.034470

H(7c) 0.494710 0.199020 −0.154600

H(12) 0.114500 0.433840 −0.068030

H(13) 0.001910 0.644630 −0.080100

H(14) 0.097350 0.865670 −0.026700

H(15) 0.304520 0.859320 0.031140

Mean−square atomic displacement parameters [Å2]Atom U11 U22 U33 U12 U13 U23

H(2a) 0.067080 0.164801 0.034814 −0.003406 0.009672 0.021281

H(2b) 0.047008 0.081276 0.079196 −0.016445 0.010400 0.003484

H(2c) 0.055653 0.081146 0.087919 0.021593 0.022022 −0.000689

H(3a) 0.094991 0.081263 0.031538 −0.016757 −0.015509 0.007878

H(3b) 0.096174 0.044382 0.054717 −0.000286 −0.001248 −0.011193

H(3c) 0.044499 0.086294 0.065182 −0.020605 −0.005018 0.001261

H(4a) 0.099086 0.069472 0.050050 0.012987 −0.013806 0.023413

H(4b) 0.045786 0.070382 0.088751 0.020397 0.000429 0.008541

H(4c) 0.082173 0.035113 0.085800 0.000611 −0.016757 0.001105

H(5a) 0.116987 0.079859 0.050388 −0.007358 −0.007397 −0.027638

H(5b) 0.106028 0.134680 0.057291 −0.066417 −0.019838 0.035802

H(5c) 0.083603 0.146861 0.055549 0.055107 −0.017472 −0.000637

H(6a) 0.073671 0.050557 0.077285 −0.022880 0.006214 −0.026130

H(6b) 0.036673 0.054730 0.118404 0.001027 0.019331 0.002782

H(6c) 0.074074 0.062699 0.066157 −0.017563 −0.000026 0.016354

H(7a) 0.057889 0.054730 0.122005 −0.000741 0.003042 −0.051857

H(7b) 0.066599 0.079599 0.070369 0.035776 −0.007059 0.001885

H(7c) 0.050544 0.063453 0.088972 0.002964 0.027404 −0.011037

H(12) 0.031213 0.032019 0.090012 −0.005473 −0.010699 −0.004979

H(13) 0.024466 0.051389 0.091546 0.004589 −0.011609 0.003991

H(14) 0.042510 0.033111 0.073983 0.015418 0.003081 0.003926

H(15) 0.041054 0.028977 0.069667 −0.003393 −0.006409 −0.008476

S3: Kappa and multipole parameters for [{2−(Me3Si)2C(Li)C5H4N}2] 8.

Symmetry forbidden multipoles are denoted by an asterisk (* )

Atom κ’ κ’ ’ Pv P11+ P11− P10

Si(2) 1.051(7) 1.00b 3.26(10) −0.05(2) 0.13(2) 0.06(2)

Si(1) 1.031(7) 1.00b 3.23(11) 0.07(2) −0.01(2) 0.02(2)

N 0.983(2) 1.00b 5.33(5) −0.009(13) −0.064(12) 0.004(11)

C(1) 0.966b 1.00b 4.52(4) 0.024(13) −0.024(13) −0.019(13)

C(2)a 0.986(3) 1.00b 4.44(6) * * 0.018(12)

C(3) 0.984b 1.00b 4.46(4) 0.06(2) 0.025(16) 0.029(17)

C(5)a 0.984(3) 1.00b 4.59(7) * * 0.014(12)

C(7) 0.985(5) 1.00b 4.54(10) 0.10(2) 0.006(17) 0.024(17)

C(11) 1.030(4) 1.00b 3.79(5) 0.000(11) 0.028(13) −0.040(14)

C(12)a 1.009(2) 1.00b 4.13(3) 0.005(11) −0.019(10) *

C(15) 1.009(2) 1.00b 4.02(4) 0.036(15) 0.040(15) *

a The multipole population coefficients of C(2), C(5) and C(12) were set equal to the corresponding coefficients of

C(4), C(6) and C(13) / C(14), respectively (chemically constrained model).

b Fixed values.

Atom P20 P21+ P21− P22+ P22−

Si(2) −0.02(2) 0.00(2) −0.01(2) −0.03(2) −0.11(2)

Si(1) −0.07(2) 0.17(2) −0.03(2) 0.05(2) 0.02(2)

N −0.119(13) 0.018(11) 0.006(11) 0.022(12) 0.019(12)

C(1) −0.029(13) −0.014(12) −0.021(12) −0.002(13) −0.045(12)

C(2)a 0.043(12) * * * *

C(3) 0.052(16) −0.042(19) 0.005(14) 0.012(16) 0.077(19)

C(5)a 0.049(11) * * * *

C(7) 0.019(16) −0.007(19) 0.049(15) 0.014(18) 0.053(19)

C(11) 0.044(15) −0.006(12) 0.016(13) −0.143(12) 0.011(11)

C(12)a −0.193(9) * * 0.007(10) 0.002(8)

C(15) −0.182(15) * * −0.021(14) 0.021(15)

a The multipole population coefficients of C(2), C(5) and C(12) were set equal to the corresponding coefficients of

C(4), C(6) and C(13) / C(14), respectively (chemically constrained model).

Atom P30 P31+ P31− P32+ P32− P33+ P33−

Si(2) −0.01(3) −0.22(3) −0.30(3) 0.06(3) 0.01(2) 0.36(3) −0.01(2)

Si(1) −0.09(3) −0.21(3) −0.43(3) 0.13(2) −0.09(3) 0.28(3) 0.04(3)

N 0.002(11) −0.013(11) −0.018(11) −0.004(10) 0.015(10) 0.137(11) 0.014(11)

C(1) −0.035(14) −0.054(13) −0.097(13) −0.015(13) 0.091(13) 0.107(13) 0.000(13)

C(2)a 0.175(13) * * * * 0.004(11) 0.127(12)

C(3) 0.176(16) −0.039(17) 0.003(14) −0.007(15) 0.006(17) −0.017(16) 0.225(16)

C(5)a 0.236(12) * * * * 0.020(11) 0.144(11)

C(7) 0.179(19) −0.065(16) 0.007(15) 0.005(17) −0.033(17) −0.047(16) 0.163(17)

C(11) 0.184(16) 0.013(14) −0.004(15) 0.180(14) −0.022(13) 0.032(12) −0.013(12)

C(12)a * 0.032(10) 0.029(9) * * 0.249(8) −0.018(11)

C(15) * 0.009(14) 0.021(14) * * 0.300(15) −0.005(15)

a The multipole population coefficients of C(2), C(5) and C(12) were set equal to the corresponding coefficients of

C(4), C(6) and C(13) / C(14), respectively (chemically constrained model).

Li H(2a)a H(3b) H(3c) H(7b) H(7c) H(12)a

κ’ 1.20b 1.20b 1.20b 1.20b 1.20b 1.20b 1.20b

κ’ ’ 1.20b 1.20b 1.20b 1.20b 1.20b 1.20b 1.20b

Pv 0.90(11) 0.888(10) 0.83(3) 0.91(3) 0.82(3) 0.94(3) 0.888(12)

P10 0.099(6) 0.06(2) 0.10(2) 0.11(2) 0.17(2) 0.125(9)

a The multipole population coefficients of all methyl group hydrogens, except for H(3b), H(3c), H(7b) and H(7c),

were set equal to H(2a) and all aromatic hydrogens equal to H(12) (chemically constrained model).

b Fixed values.

S4: Local coordinate systems for [{2−(Me3Si)2C(Li)C5H4N}2] 8 before normalization.

C1 Li*

C11

C12

C13 C14

C15

Nz

y

y x

x y

x y

x

y x

y

The following local coordinate systems (right handed setting) were adapted:C11 [z axis: C11 � N; y axis: C11 � C12], C12 [x axis: C12 � C11; y axis: C12 � C13], C13 [x axis: C13 � C12; y axis: C13 � C14], C14 [x axis: C14 � C13; y axis: C14 � C15], C15 [x axis: C15 � C14; y axis: C15 � N], N [x axis: N � C11; y axis: N � C15].For the carbon atoms C12, C13, C14 and C15 the z−axes are located perpendicular to a pseudo mirror plane.

C11

C1Li

Si2

C7 C6

C5

y x

Si1

y x

x

y

z

z

y

y z

y

C3

C3

C1

Li

Si1

C3 C2

C4

y

x

Si2

y

x

x

y

z

z

y

y

z y

C3

C3

C11

The following local coordinate systems (right handed setting) were adapted:Li [x axis: Li � C1; y axis: Li � Si2], C1 [x axis: C1 � Si2; y axis: C1 � Si1], Si2 [x axis: Si2 � C7; y axis: Si2 � C1], Si1 [x axis: Si1 � C3; y axis: Si1 � C1], C2 [z axis: C2 � Si1; y axis: C2 � C1], C3 [z axis: C3 � Si1; y axis: C3 � C1], C4 [z axis: C4 � Si1; y axis: C4 � C1], C5 [z axis: C5 � Si2; y axis: C5 � C1], C6 [z axis: C6 � Si2; y axis: C6 � C1], C7 [z axis: C7 � Si2; y axis: C7 � C1].For the carbon atoms C5, C6, C2 and C4 the z−axes are oriented along the pseudo 3−fold axes.

S5a: Model deformation density maps after multipole refinement for

[{2−(Me3Si)2C(Li)C5H4N}2] 8.

Contour level: 0.05 e Å−3

C1C12

C13

C14

C15

N

H15

H14

H13

H12

C11

Si2

C1

Li

S5b: Residual density maps after multipole refinement for [{2−(Me3Si)2C(Li)C5H4N}2] 8.

Data cut−off at sinΘ/λ = 0.8 Å−1; contour level: 0.05 e Å−3.

Li Si2

C1

C1

C11

C12

C13

C14

C15

N

H15

H14

H13

H12

S6: Compar ison of multipole models for [{2−(Me3Si)2C(Li)C5H4N}2] with different flexibility.

• Model 1:

as described in the Experimental Part

• Model 2:

as Model 1 but without chemical constraints and without imposing selection picking rules for

the multipoles.

Topological analysis and geometr ical parameters of the agostic fragment

Unit Distance [Å] ρ(r c) [e/Å3] ∇2ρ(r c) [e/Å5] Ellipticity ε

Li···N_a 1.9509 0.210(2) 5.202(2) 0.02

Li−C1 2.2050 0.142(2) 2.515(1) 0.10

C1−Si2 1.8592(4) 0.855(15) 1.83(3) 0.17

Si2−C7 1.8946(6) 0.686(17) 4.81(3) 0.04

C7−H7c 1.0981 1.72(5) −13.06(11) 0.09

• Model 3:

as Model 1 but with hexadecapole refinement, in addition.

Topological analysis and geometr ical parameters of the agostic fragment

Unit Distance [Å] ρ(r c) [e/Å3] ∇2ρ(r c) [e/Å5] Ellipticity ε

Li···N_a 1.9510 0.210(4) 5.110(4) 0.06

Li−C1 2.2049 0.147(4) 2.449(3) 0.33

C1−Si2 1.8591(4) 0.870(17) 1.93(3) 0.24

Si2−C7 1.8940(6) 0.733(18) 4.97(3) 0.08

C7−H7c 1.0981 1.74(5) −15.81(15) 0.10

S7: Topological analysis and geometr ical parameters of the calculated model systems 1, 2, 3,

4, 5, 10 and 11.

System Basisa d(C−Y)b

[Å]ρ(r c)[e/Å3]

∇2ρ(r c)[e/Å5]

Ellipticity L(CC1) / L(CC2)[e/Å5]

CH3−CH3 1 I 1.531 1.60 −12.79 0.00 25.5 / 20.0

II 1.531 1.60 −12.79 0.00 25.4 / 19.9

III 1.531 1.63 −13.38 0.00 26.5 / 19.8

CH2CH3− 2 I 1.535 1.53 −10.97 0.14 22.0 / 14.0

II 1.531 1.56 −11.55 0.10 18.0 / 15.5

III 1.525 1.60 −12.31 0.10 17.0 / 16.4

CH2=CH2 3 I 1.327 2.32 −24.86 0.33 − / 27.6

II 1.329 2.32 −24.78 0.33 − / 27.6

III 1.324 2.41 −27.15 0.33 − / 29.3

CH2−SiH3− 4 I 1.783 0.90 7.89 0.29 15.5 / 15.6

II 1.790 0.89 7.66 0.25 14.4 / 15.9

III 1.781 0.93 6.45 0.27 17.0c

EtLi 5 I 1.543 1.53 −11.26 0.06 18.9 / 16.3

II 1.544 1.53 −11.23 0.06 18.8 / 16.3

III 1.540 1.56 −11.81 0.06 18.8 / 16.8

CH2=SiH2 10 I 1.707 0.99 12.99 0.49 − / 20.3

II 1.708 0.99 12.92 0.49 − / 20.2

III 1.702 1.03 11.05 0.50 − / 20.3

CH3−SiH3 11 I 1.885 0.80 4.86 0.00 24.1 / 18.8

II 1.885 0.80 4.85 0.00 24.0 / 18.7

III 1.878 0.83 3.56 0.00 25.1 / 18.5a The theoretical calculations were performed at the B3LYP/6−311G(d,p) (I), the B3LYP/6–311+G(d,p) (II) and the

B3LYP/6–311++G(3df,3pd) (III) level of theory, respectively. b Y = C, Si. c At this level of theory charge

concentrations CC(1) and CC(2) are merged into one broad feature as observed in the experimental study of 8.

S8a: Geometr ical and topological parameters of the calculated model system 6

[B3LYP/6−311G(d,p) and B3LYP/6−311+G(d,p) in square brackets, respectively].

Li−C1 1.991 [1.993] Li−C1−Si 88.0 [88.0]C1−Si 1.834 [1.834] C1−Si−C2 107.8 [107.8]Si−C2 1.946 [1.947] Si−C2−H2a 111.9 [112.0]C2−H2a 1.093 [1.094] Si−C2−H2b 112.6 [112.6]C2−H2b 1.104 [1.104] Si−C2−H2c 112.6 [112.6]C2−H2c 1.104 [1.104] Li−C1−Si−C2 0.0 [0.0]

2.258 [2.256] Li−Si−C2−H2a 180.0 [180.0]Li···H2c 2.258 [2.256]

Selected distances [Å] and angles [deg]

Li···H2b

Unit EllipticityLi−C1 0.28 [0.28] 4.76 [4.68] 0.09 [0.09]C1−Si 0.85 [0.85] 5.85 [5.88] 0.17 [0.17]Si−C2 0.70 [0.70] 4.40 [4.36] 0.02 [0.01]

ρ(rc) [e/Å3] ∇2ρ(r

c) [e/Å5]

Li

SiC1

H2b

H2aC2

H2c

CC(2):L(r) = 14.91 [14.93] e/Å5

ρ(r) = 1.62 [1.62] e/Å3

CC(1):L(r) = 16.14 [16.03] e/Å5

ρ(r) = 1.66 [1.66] e/Å3

S8b: Geometr ical and topological parameters of the calculated model system 6a.

I 14.56 1.64 16.16 1.70II 16.81 1.73III 18.03 1.79

Basisa L(CC1) [e/Å5] ρ(CC1) [e/Å3] L(CC2) [e/Å5] ρ(CC2) [e/Å3]

b b

b b

Si

C1

C2CC(2)

CC(1)

Unit Ellipticity

C1−Si I 1.773 0.91 8.55 0.29II 1.778 0.90 8.55 0.26III 1.771 0.94 7.12 0.27

Si−C2 I 1.953 0.69 4.01 0.02II 1.942 0.71 4.06 0.02III 1.933 0.74 3.03 0.03

Basisa Distance [Å] ρ(rc) [e/Å3] ∇2ρ(rc) [e/Å

5]

a The theoretical calculations were performed at the B3LYP/6−311G(d,p) (I), the B3LYP/6−311+G(d,p) (II)

and the B3LYP/6−311++G(3df,3pd) (III) level of theory, respectively. b At these levels of theory charge

concentrations CC(1) and CC(2) are merged into one broad feature as observed in the experimental study of 8.

S8c: Geometr ical and topological parameters of the agostic fragment

in the calculated system Li[HC(SiMe3)2] 7 [B3LYP/6−311G(d,p)].

Li−C1 2.00 C2−H2c 1.10 Si1−C1−Si2 128.0C1−Si1 1.83 Li···H2b 2.35 Si1−C2−H2a 110.4C1−Si2 1.83 Li···H2c 2.17 Si1−C2−H2b 113.9Si1−C2 1.95 Li−C1−Si1 87.4 Si1−C2−H2c 113.5Si1−C3 1.90 Li−C1−Si2 87.4 Li−C1−Si1−C2 7.2Si1−C4 1.89 C1−Si1−C2 107.5 Li−Si1−C2−H2a −173.8C2−H2a 1.09 C1−Si1−C3 119.6C2−H2b 1.10 C1−Si1−C4 111.6

Selected distances [Å] and angles [deg]

Unit EllipticityLi−C1 0.26 4.54 0.11C1−Si1 0.84 6.39 0.14Si1−C2 0.70 4.30 0.02Si1−C3 0.78 4.77 0.01Si1−C4 0.79 4.96 0.01

ρ(rc) [e/Å3] ∇2ρ(r

c) [e/Å5]

Li

C1

Si1

C4

C2

C3

H2c

H2b

Si2

H2a

CC(2):L(r) = 14.90 e/Å5

ρ(r) = 1.65 e/Å3

CC(1):L(r) = 13.59 e/Å5

ρ(r) = 1.60 e/Å3

S8d: Geometr ical and topological parameters

of the calculated model system 9 [B3LYP/6−311G(d,p)].

Li−C1 2.00 C2−H2c 1.10 Si−C4−H4a 110.8C1−Si 1.85 Li···H2c 2.61 Si−C4−H4b 113.9Si−C4 1.95 C1−C2 1.55 Si−C4−H4c 113.4C4−H4a 1.09 C1−C3 1.53 C1−C2−H2b 111.6C4−H4b 1.11 Si−C5 1.91 C1−C2−H2c 113.9C4−H4c 1.10 Si−C6 1.90 Li−C1−Si−C4 −17.0

2.11 Li−C1−Si 85.3 Li−Si−C4−H4a 172.8Li···H4c 2.31 C1−Si−C4 105.5 Li−C1−C2−H2c 38.7

Selected distances [Å] and angles [deg]

Li···H4b

Unit EllipticityLi−C1 0.29 4.33 0.10C1−Si 0.88 3.99 0.19Si−C4 0.70 3.20 0.03Si−C5 0.77 4.66 0.01Si−C6 0.78 4.95 0.02C1−C2 1.52 −10.54 0.09C1−C3 1.57 −11.59 0.07

ρ(rc) [e/Å3] ∇2ρ(r

c) [e/Å5]

Li

C1 Si

C4

C2

C3 C5

C6

H4b

H4c H4a

H2c

H2b

CC(1):L(r) = 18.01 e/Å5

ρ(r) = 1.73 e/Å3

CC(2):L(r) = 16.03 e/Å5

ρ(r) = 1.66 e/Å3

S9: Ellipticity angle along the C1−Si2 bondpath of 8 (theo).

(the eigenvector v2 of the Hessian matrix of ρ(r ) corresponds to the major axis of curvature)

0

20

40

60

80

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6

BCPSi2C1

0 0.2 0.6−0.6 −0.2−1.0

0

20

40

60

80

Distance from the Bond Critical Point / Å

Ang

le b

etw

een

v 2

and

the

plan

e Li

,C1,

Si2

/ de

g