S-1

Reactivity of the Triple Ion and Separated ion pair of Tris(trimethylsilyl)methyllithium withAldehydes – a RINMR Study

Amanda C. Jones, Aaron W. Sanders, William H. Sikorski, Kristin L. Jansen, Hans J. Reich* Department of Chemistry, University of Wisconsin Madison, WI 53706

Supporting InformationTable of Contents

S1. General Experimental. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

S2. RINMR ExperimentsPreparation of Solutions of Tris(trimethylsilyl)methyllithium (1). . . . . . . . . . . . . . . . . . . . . . . . 3Reaction 1S and 1C with MeI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Reaction of 1T with MeI at Various Temperatures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Activation Parameters for the Dissociation of 1T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Reaction of 1 with 3,5-Bis(trifluoromethyl)benzaldehyde (2) at ca -132 °C. . . . . . . . . . . . . . . . 6Reaction of 1 with Benzaldehyde and p-Fluorobenzaldehyde (3) at ca -132 °C. . . . . . . . . . . . . 7Reaction of 1T with 3,5-Bis(trifluoromethyl)benzaldehyde (2) at Various Temperatures . . . . . 8Reaction of 1T with p-Fluorobenzaldehyde (3) at Various Temperatures. . . . . . . . . . . . . . . . . . 9Reaction of 1T with p-Dimethylaminobenzaldehyde (4a) at -80 °C. . . . . . . . . . . . . . . . . . . . . 11Reaction of 1T with p-Diethylaminobenzaldehyde (4b) at various Temperatures. . . . . . . . . . 12Activation Parameters for the Reaction of Aldehydes (2, 3, 4b) with 1T. . . . . . . . . . . . . . . . . 15Reaction of 1T with HMPA at -86 °C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Reaction of 1T with p-Dimethylaminobenzaldehyde (4a) in THF/Me2O/HMPA. . . . . . . . . . . 17Reaction of 1S-HMPA with 3,5-Bis(trifluoromethyl)benzaldehyde (2) . . . . . . . . . . . . . . . . . . 18Reaction of 1S-HMPA with p-Fluorobenzaldehyde (3). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Reaction of 1S-HMPA with p-Diethylaminobenzaldehyde (4b) at Various Temperatures. . . . 20

S3. Competition Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

S4. SynthesesTris(trimethylsilyl)phenylselenomethane (1-SePh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231,1,1-Tris(trimethylsilyl)ethane (1-Me). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Tris(trimethylsilyl)(methylthio)methane (1-SMe). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Tris(trimethylsilyl)(ethylthio)methane (1-SEt). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241,1-Bis(trimethylsilyl)-2-arylethenes (5). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

S5. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

H

Me3Si SiMe3

CF3

CF3

H

Me3Si SiMe3

H

Me3Si SiMe3

Me2N

H

Me3Si SiMe3

Et2N

5a 5b 5c 5e

H

Me3Si SiMe3

F

5d

CF3

F3C

F Me2N

H

O

H

O

H

O

2 3 4a 4b

Et2N

H

O

Me3Si

Me3SiC:-//Li+Me3Si

Me3Si

Me3SiLiCMe3Si

1C 1S 1T

Me3Si

Me3SiLiMe3Si

SiMe3

SiMe3

SiMe3

Li+

S-2

S1. General Experimental

Tetrahydrofuran (THF) and diethyl ether (ether) were freshly distilled from sodium benzophenone ketylbefore use. Glassware was placed overnight in a 110 °C oven or flame-dried before purging with N2 toremove moisture. Common lithium reagents were titrated using n-propanol in THF with 1,10-phenanthrolineas an indicator.[S1] Temperatures of -78 oC were achieved with a dry ice/acetone bath and -20 oC with achemical freezer. NMR tubes, injection needles and syringes were kept dry by storing them in an evacuatedglove box antechamber. Probe temperatures were measured internally with 5-10 :L of the 13C chemical shiftthermometer (Me3Si)3CH (10% 13C enriched).[S2] This material contributes to the varying fractions of 1-Hin each sample, the relative amount dependant upon the concentration of 1. This material was prepared bydiluting 13CHCl3 with 9 volumes of natural abundant CHCl3 and converting to (Me3Si)3CH using theprocedure of Yus and Guijarro, or by diluting (Me3Si)313CH with 9 volumes of natural abundant material.[S3]

Commercially available starting materials and reagents were obtained from Aldrich Chemical Companyand included: iodomethane, 3,5-bis(trifluoromethyl)benzaldehyde (2), p-fluorobenzaldehyde (3), p-dimethylaminobenzaldehyde (4a), p-diethylaminobenzaldehyde (4b), diethyl disulfide.Tris(trimethylsilyl)methane was purchased, or prepared by reductive silylation of CHCl3.[S3]

S2. RINMR Experiments

The apparatus and techniques for performing RINMR experiments have been described previously.[S4]Low-temperature RINMR experiments were performed on a 360 MHz spectrometer witha 10 mm broadband probe. 1H RINMR spectra were observed through the decoupler channel tuned to360.132 MHz. Spectra were obtained in non-deuterated ether solvents with the spectrometer unlocked andwere referenced internally to the trimethylsilyl peak of Me3SiPh (* 0.27).

The temperature of the RINMR sample is checked at the beginning and the end of an RINMR experiment.For many experiments, the probe temperature was raised a few degrees ca 10 s prior to the injection. Thisoffsets the warming that results from the injection itself. The size of the offset has been determined in anumber of control cases[S4] and depends on the injection volume. There is approximately a 1° temperaturejump for a 0.05 mL injection. Single scan 1H RINMR spectra were typically collected with a 1 s acquisitiontime and a 14 ppm sweep width. For fast reactions, initial spectra were collected with a 0 s delay betweenspectra. A longer delay (15-60 s) was selected for the remainder of an experiment if/when the reaction rateswere slower.

Individual spectra were processed using NUTS data processing software (Acorn NMR, Inc.). Peak areaswere determined using the NUTS line fitting routine. The concentrations of 1 were determined relative toPhSiMe3 using spectra prior to the injection but included the added volume from the injection. Substrateconcentrations are reported as the external concentration of the solution to be injected, as well as the initialinternal concentration after the solution has been injected into the sample (i.e., the in situ concentration). The solvent composition is reported uniformly as 3:1 THF/Me2O, however, each sample contains #3%hexanes (from the n-BuLi used to prepare 1) and in some cases #3% Et2O from the solution injected. Whilethese deviations are not reported, the solvent composition was measured using quantitative 13C NMR andtaken into account for both concentration and temperature calculations.

Preparation of Solutions of Tris(trimethylsilyl)methyllithium (1) for RINMR Experiments. A 10mm NMR tube sawed to a length of 18 cm was sealed with a greased septum and parafilm and purged withargon. The 13C chemical shift thermometer (10% 13C labeled tris(trimethylsilyl)methane (1-H), 4 :L),[S2] aninternal s tandard for concentra t ions (PhSiMe3 , 28 mg, 0 .186 mmol) andtris(trimethylsilyl)phenylselenomethane (1-SePh) (0.02 g-0.1 g, 0.05 mmol - 0.26 mmol) were weighed inusing Hamilton syringes, followed by addition of 1 mL of freshly distilled THF. The NMR tube was cooledin a dry ice/acetone bath. Me2O (3 mL) was distilled via cannula into the NMR tube from a graduated conicalcylinder containing n-BuLi (for drying). n-BuLi in hexanes (2.5 M, 0.02-0.1 mL) was added by syringe to

S-3

0.3 0.2 0.1 0.0 -0.1 -0.2ppm

1-H(Me3Si)3C-H

1T

1-Me(Me3Si)3CMe

9.54

20.14

30.74

51.94

t / s

1.06

0

2.12

4.24

1T 1C 1S

1-SePh(Me3Si)3CSePh

1H

kobs1C = 0.035 s-1

kobs1S ≥ 2.8 s-1

T = -133 °C (measured)

[MeI] = 0.08 M

0 30 60 90 120t / s

0

2

4

6

8

10

12

Con

cent

ratio

n / m

M

Legend1S1C

Me3Si

Me3SiC:-//Li+Me3Si MeI

Me3Si

Me3SiMeCMe3Si

Me3Si

Me3SiLiCMe3Si

1-Me1C 1S

form 1. Reactions to monitor the reactivity of 1T were typically done at higher concentrations ($ 0.05 M 1)where the triple ion comprised ca 40% of the total concentration of 1. Reactions to monitor the reactivity of1C and 1S were done at low concentration (#0.02 M 1) where the triple ion comprised ca 20 % of the totalconcentration of 1.

1H RINMR Spectroscopy of the Reaction 1S and 1C with MeI. MeI (0.1 mL, 3.5 M in 1:1 THF/Et2Oor NEAT) was injected into a solution of 1 (0.017 M) in 4 mL of 1:3 THF/Me2O at -133 °C (Fig. S-1). Thespectrometer was not warmed during the injection, so the experimental temperature is expected to be ca -132°C. The separated ion 1S has reacted when the first spectrum was acquired after the injection (1 s), so toestimate a lower limit for the rate we assume #5% of the initial concentration of 1S is present without beingdetectable. The triple ion 1T does not react on this time scale. 1H NMR spectra and a time vs concentrationplot for a similar experiment with injection of 0.1 mL of MeI (20 equiv) are shown in the body of thecommunication (Fig. 1).

Figure S-1. 1H NMR spectra and time vs concentration plot for the injection of MeI as a 3.5 M solutionin 1:1 THF/Et2O (0.08 M in situ) into a solution of 1 (0.016 M) in 4 mL of 1:3 THF/Me2O at -133 °C (initialtemperature).

S-4

1H RINMR Spectroscopy for the Reaction of 1T with MeI at Various Temperatures. MeI (0.1 mL,5.6 M THF) was injected into a solution of 1 (0.07 M) in 4 mL of 1:3 THF/Me2O at -78 °C, -86 °C and -96°C. Representative 1H NMR spectra and first order plots are shown in Fig. S-2. A series of experiments atseveral temperatures showed that the reaction rate was independent of [MeI].

Figure S-2. (a) 1H NMR spectra for injection of 0.1 mL a 5.6 M THF solution of MeI (0.13 M in situ)into a solution of 1 (0.06 M) in 4 mL of 1:3 THF/Me2O at -96 °C. (b) First order plots for the 0.1 mLinjections of a 5.6 M THF solution of MeI (0.13 M in situ) into solutions of 1 (0.06-0.07 M) in 1:3THF/Me2O at -77 °C, -86 °C and -96 °C.

t / s PhSiMe3 1T

1C

1T

1H

0.2 0.0 -0.20

6.6

19,789

30,573

33,675

36,776

39,877

42,979

49,182

55,385

61,588Inject 0.1 mL solution

(5.6 M / THF)

MeI Me3Si

Me3SiCH3CMe3Si

1S

1-Me

Triple Ion Rates

0.00E+00 2.00E+04 4.00E+04 6.00E+04 8.00E+04t / s

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Ln([1

T]0/[

1T] t)

k1TI = 28 10-5 s-1

k1TI = 3.1 10-5 s-1

k1TI = 0.88 10-5 s-1

LegendT= -78 °C

T= -86 °CT= -96 °C

T = -95.5 °C

1-Me1T0.07 M

1:3 THF/Me2O

1-H

(a)

(b)

Me3Si

Me3SiLiMe3Si

SiMe3

SiMe3

SiMe3

Li+

S-5

170 175 180 185 190 195 200T / K

12.00

13.00

14.00

15.00

16.00

17.00

ΔG /

kcal

/mol

Me3Si

Me3SiLiMe3Si

SiMe3

SiMe3

SiMe3

Li+

k11T

MeI

Me3Si

Me3SiMe3Si Li

ΔS = -7.3 cal/mol KΔH = 13.1 kcal/mol

RDS

Me3Si

Me3SiMe3Si Me

Li+SiMe3

SiMe3Me3Si

C

Inject HMPA

Inject MeI

HMPA

Li(HMPA)4+SiMe3

SiMe3Me3Si

C

Activation Parameters for the Dissociation of 1T as Measured by the Reaction with MeI. Activationparameters were determined by converting first order rate constants (Fig. S-2b) to )G‡ using the equation:)G‡= 1.987*T*[23.76+Ln(T/k)]. The plot of T vs. )G‡ is shown in Fig. S-3. At -132 °C, k1T is calculatedfrom the equation k1T = e(23.76+ln(T)-)G/(1.987*1.987)) = 4@10-10 s-1. Because the triple ion does not react with MeIfaster than it dissociates to the monomers, this rate can be used as an upper limit on the possible rate ofreaction of 1T with MeI. Comparison to the mixing-limited rate of 1S (k1S-MeI $2 s-1) indicates that 1S is atleast 5@1010 times as reactive as 1T with MeI.

Figure S-3. Eyring plot for the first order reaction of 1T with MeI and HMPA in 3:1 Me2O/THF.

S-6

1H RINMR Spectroscopy of the Reaction of 1 with 3,5-Bis(trifluoromethyl)benzaldehyde at ca -132°C. 3,5-Bis(trifluoromethyl)benzaldehyde (2) (0.1 mL, 1.1 M in 1:1 THF/Et2O) was injected into a solutionof 1C and 1S (0.017 M) in 4 mL of 1:3 THF/Me2O at -134 °C (Fig. S-4). The spectrometer was not warmedduring the injection so the actual temperature is expected to be ca -132 °C. To determine kobs1S we estimatean undetectable 5% of the initial concentration of 1S present at the second spectrum (t = 1 s). The triple ionwas monitored for 4 h and showed negligible change in concentration. In the following aldehydeexperiments, the signals labeled “LiOSiMe3" were not securely identified as such, and sometimes changedfrom early to later parts of the experiment.

Figure S-4. (a) 1H NMR spectra and (b) plot of 1S and 1C disappearance for the 0.1 mL injection of a 1.1M THF solution of 2 (0.027 M in situ) into a solution of 1 (0.017 M) in 4 mL of 1:3 THF/Me2O at ca -132°C.

C LiMe3Si

Me3SiMe3Si

17 mM 1

H

CF3

F3C

Me3Si SiMe3

+ LiOSiMe3

0.0 10.0 20.0 30.0 40.0 50.0 60.0Time / sec

0.0

2.0

4.0

6.0

8.0

10.0

Con

cent

ratio

n / m

M

kobs1C = 0.05 s-1

T = -133 °C

kobs1S = 2.7 s-1

[2] = 0.027 M in situ

Legend 1S 1C

0.2 0.0 -0.2ppm

1-H 1T 1S1C-1.03

0

1.03

2.06

3.1

4.1

5.2

6.2

7.2

9.3

11.3

17.5

19.6

27.8

38.1

48.4

60.8

t / s1H

5c

1T1-H LiOSiMe3

1C

5c1:3 THF/Me2O

(a)

(b)

CF3

F3C H

O

2

S-7

1H RINMR Spectroscopy of the Reaction of 1 with Benzaldehyde and p-Fluorobenzaldehyde (3).Benzaldehyde (0.1 mL, 1.2 M in 1:1 THF/Et2O) was injected into a solution of 1 (0.018 M) in 4 mL of 1:3THF/Me2O at -134 °C (Fig. S-5). The spectrometer was not warmed during the injection so the actualtemperature is expected to be ca -132 °C.

A solution of 3 (0.1 mL, 7.5 M in Et2O) was injected into a solution of 1 (0.018 M) in 1:3 THF/Me2O at-135 °C. The spectrometer was not warmed during the injection. The two-phase behavior in thedisappearance of 1C is attributed to the effect of the initial sample warming due to injection, followed byefficient cooling.

Figure S-5. Time vs concentration plots for the injection of (a) benzaldehyde (0.1 mL, 1.2 M in 1:1THF/Ether) and (b) p-fluorobenzaldehyde (3) (0.1mL, 7.45 M in 1:1 THF/ether) into a solution of 1 (0.018M) in 4 mL of 1:3 THF/Me2O. (c) Selected 1H NMR spectra for the experiment with (3)

0 30 60 90 120t / s

0

5

10

[1C

] and

[1S]

/ m

M

0 30 60 90 120t / s

0

2

4

6

8

10

12

[1C

] and

[1S]

/ m

M

kobs1C = 0.028 s-1

T = -134 °C

T = -135 °C

Me3Si

Me3SiLiCMe3Si Ar

0.018 M1:3 THF/Me2O

H

O

Ar H

Me3Si SiMe3

0.1 mL

kobs1C = 0.039 s-1

kobs1C = 0.009 s-1

0.2 0.0 -0.2ppm

0

1.6

2.3

3.1

3.9

4.7

5.5

6.2

10

14

30

45

61

76

92

108

139

170

186

t / s

1HLiOSiMe3

1-H1T

1C

1-H 1T 1C1S

0.8

5d

(a) [PhCHO] = 0.03 M

(b) [3] = 0.18 M

kobs1S = 3.5 s-1

Legend 1S 1C

kobs1S ≥ 3 s-1

5d (Ar = p-F-C6H4)Ar = p-F-C6H4 (3)or

Ar = Phor

5e (Ar = Ph)

(c)

[3]0 = 0.18 M

S-8

Me3Si

Me3SiLiCMe3Si

SiMe3

SiMe3

C SiMe3

Li+

k21T-2

k11T 1S + 1C

H

Me3Si SiMe3

F3C

CF3

+ LiOSiMe3

2

2

5ckobs1T = k21T-2 [2] + k11T

1H RINMR Spectroscopy of the Reaction of 1T with 3,5-Bis(trifluoromethyl)benzaldehyde (2) atVarious Temperatures. Six trials of RINMR experiments were run with 1 and 2 in 4 mL of 1:3 THF/Me2O,at three different temperatures: -95 °C, -87 °C, -73 °C. The reactions of 1S and 1C are too fast to measure.An average order in 2 of n = 0.7 was determined from plots of ln[2] vs ln[kobs1T]. The order less than 1indicates the pathway of zero order (in aldehyde) dissociation of 1T to 1S and 1C significantly competes withthe second order process. The first and second order rate constants (k21T-2 and k11T) were determined for eachtemperature from plots of [2] vs. kobs1T. The aldehyde was injected as a solution in 1:1 THF/Et2O.Representative 1H NMR spectra are shown in Fig. S-6. The rate data are shown in Table S-1.

Figure S-6. 1H NMR spectra for the 0.1 mL injection of a 3.8 M THF/Et2O solution of 2 (0.76 M in situ)into a 0.05 M solution of 1 in 4 mL of 1:3 THF/Me2O at -95 °C.

C LiMe3Si

Me3SiMe3Si

1:3 THF:Me2O, T = -94 °C

H

Me3Si SiMe3

+ LiOSiMe3

F3C

CF3

0.2 0.0 -0.2ppm

0

9.3

92

246

296

3,371

6,477

12,689

20,355

32,241t/s

1C 1S

1H

0.76 M 2

1T1-H

1T1-H

5c

5c

0.05 M 1

CF3

F3C H

OLiOSiMe3

S-9

Me3Si

Me3SiLiCMe3Si

SiMe3

SiMe3

C SiMe3

Li+

k21T-3 H

Me3Si SiMe3

+ LiOSiMe3

3

Fkobs1T = k21T-3 [3] 5d

Table S-1. Rate constants for the injections of 2 into solutions of 1 (0.05-0.06 M) in 4 mL of 1:3 THF/Me2O.

T / °C kobs1T / s-1 [2] / mMa k11T / s-1 k21T-2 / M-1 s-1 n

-95 1.5 @ 10-5 50

-94 4.8 @ 10-5 270 7.7 @ 10-6 1.5 @ 10-4 0.8

-87 5.5 @ 10-5 60

-87 11.8 @ 10-5 300 3.9 @ 10-5 2.6 @ 10-4 0.5

-78 1.6 @ 10-4 b

-73 34 @ 10-5 50

-73 150 @ 10-5 360 1.4 @ 10-4 3.7 @ 10-3 0.8a The reported concentration of 2 is calculated following the reaction of 1S and 1C.b Extrapolated rate constant used for the relative rates reported in Fig. 2 in the main body of thecommunication.

1H RINMR Spectroscopy of the Reaction of 1T with p-Fluorobenzaldehyde (3) at VariousTemperatures. Seven trials of RINMR experiments were run with 1 and 3 in 4 mL of 1:3 THF/Me2O, at fourdifferent temperatures: -105 °C, -95 °C, -82 °C, -87 °C. The reactions of 1S and 1C are too fast to measure.An average order in 3 of n=1.1 was determined from plots of ln[3] vs ln[kobs1T]. The first order behaviorindicates that the dissociation of 1T to 1S and 1C does not compete significantly with the second orderprocess. Second order rate constants (k21T-3) were determined from plots of [3] vs. kobs1T. The aldehyde 3 wasinjected either as a solution in 1:1 THF/Et2O or pure THF. Representative 1H NMR spectra and conditionsare shown in Fig. S-7. The rate data are shown in Table S-2.

S-10

Figure S-7. 1H NMR spectra for the 0.2 mL injection of a 7.2 M THF solution of 3 (0.3 M in situ) intoa 0.04 M solution of 1 in 4 mL of 1:3 THF/Me2O at -95 °C.

Table S-2. Rate constants for the injections of 3 into solutions of 1 (0.04-0.06 M) in 4 mL of 1:3 THF/Me2O.

T / °C kobs1T / s-1 [3] / mMa k21T-3 / M-1 s-1 n

-105 1.6 @ 10-5 40

-104 9.7 @ 10-5 210 4.9 @ 10-4 1.2

-94 8.2 @ 10-5 40

-95 57 @ 10-5 270 2.1 @ 10-3 1.1

-87 2.4 @ 10-3 230 0.011 b N/A

-83 0.8 @ 10-3 30

-83 7.4 @ 10-3 360 0.02 0.9

-78 0.039 ca The reported concentration of 3 is calculated following the reaction of 1S and 1C.b A second order rate constant was estimated using the equation kobs1T/[3].c Extrapolated rate constant used for the relative rates reported in Figure 2 in the main body of thecommunication.

C LiMe3Si

Me3SiMe3Si

0.04 M 1

H

Me3Si SiMe3

+ LiOSiMe3

F

0.4 0.2 0.0 -0.2ppm

0

0.5

2.5

18.8

79.7

181.2

1,683

3,184

4,686

6,187

PhSiMe3

1-H1T

1C 1S

t / s LiOSiMe3

5d1-H

1T

PhSiMe31H

0.29 M 3

5d1:3 THF/Me2O, -95 °C

H

F

O

S-11

1H NMR Spectroscopy for the Reaction of 1T with p-Dimethylaminobenzaldehyde (4a) at -80 °Cin THF/Me2O. p-Dimethylaminobenzaldehyde (0.25 mL, 0.6 M or 1.5 M THF) was injected into a solutionof 1 (0.022-0.024 M) in 4 mL of 1:3 THF/Me2O at ca -80 °C. An order of 1.1 in 4a was determined from aplot of ln[4a] vs ln[kobs1T]. A second order rate constant (k21T-4a) was determined from a plot of [4a] vs. kobs1T.Representative spectra and plots of triple ion disappearance are shown in Fig. S-8. The rate data are listedin Table S-3.

Figure S-8. (a) 1H NMR spectra for the 0.25 mL injection of a 0.6 M THF solution of [4a] (0.03 M insitu) into a 0.022 M solution of 1 in 4 mL of 1:3 THF/Me2O at -79 °C and (b) raw plots for the decay of tripleion after two injections of 4a into a solution of 1 in 4 mL of 1:3 THF/Me2O..

Table S-3. Rate data for the injections of 4a into solutions of 1 (0.022-0.024 M) in 4 mL of 1:3 THF/Me2O.

T / °C kobs1T / s-1 [4a] / mM k21S-4a / M-1 s-1 n

-79 0.005 17

-80 0.017 86 0.32a 1.1a Used for the relative rates reported in Figure 2 of the main body of the paper.

0.0 100.0 200.0 300.0 400.0 500.0Time / s

0.0

2.0

4.0

6.0

8.0

[1T]

/ m

M

Legend[4a] = 0.054 M kobs1T = 0.017 s-1

[4a] = 0.017 M kobs1T = 0.005 s-1

(b)

Inject 0.25 mL0.6 M - 1.5 M THF

-79 °C

0.2 0.0 -0.2ppm

0

6.1

12.2

36.4

46.5

48.5

68.7

88.9

129.3

170

210

T / s

PhSiMe31-H

5a

1T LiOSiMe3

1H

1T1-H1C 1S

[4a]o = 0.03 M

(a)

C LiMe3Si

Me3SiMe3Si

H

O

NH

Me3Si SiMe3

+ LiOSiMe3N

5a

4a

0.022-0.024 M

S-12

Me3Si

Me3SiLiCMe3Si

SiMe3

SiMe3

C SiMe3

Li+

k21T-4b H

Me3Si SiMe3

+ LiOSiMe3

4b

Et2Nkobs

1T = k21T-4b [4b] 5b

1H RINMR Spectroscopy of the Reaction of 1 with p-Diethylaminobenzaldehyde (4b) at VariousTemperatures. Aldehyde 4b (0.2-0.3 mL, 1.2-7.1 M THF) was injected into a solution of 1 (0.04-0.07 M)in 4 mL of 1:3 THF/Me2O at -131 °C, -93 °C , -87 °C and -81 °C. At T$-93 °C, the reaction of 1S and 1Care too fast to measure. The experiment at -131 °C is described in further detail below.

For the reaction of 1T at the various temperatures, an average order in 4b of n=1 was determined fromplots of ln[4b] vs ln[kobs1T]. The first order behavior indicates that dissociation of 1T to 1S and 1C does notcompete significantly with the second order process. Second order rate constants (k21T-4b) were determinedfrom plots of [4b] vs. kobs1T. Representative 1H NMR spectra and conditions are shown in Fig. S-9. The ratedata are shown in Table S-4.

Figure S-9. 1H NMR spectra for the 0.25 mL injection of a 1.8 M THF solution of 4b (0.08 M in situ) intoa 0.07 M solution of 1 in 4 mL of 1:3 THF/Me2O at -93 °C.

C LiMe3Si

Me3SiMe3Si

0.07 M 11:3 THF:Me2O, -93 °C

H

Me3Si SiMe3

+ LiOSiMe3

Et2N

0.2 0.0 -0.2ppm

5b

1-H 1T

0

2

4.1

6.1

20.3

40.6

81

183

386

589

792

995

1,198

t / s

1T1-H 1C 1SPhSiMe3

1H PhSiMe3

0.08 M 4b

5b

LiOSiMe3

S-13

Table S-4. Rate constants for injections of 4b into solutions of 1 (0.04-0.06 M) in 4 mL of1:3 THF/Me2O.

T / °C kobs1T / s-1 [4b] / mMa k21T-4b / M-1 s-1 n

-131 1.3 @ 10-5 45

-130 2.8 @ 10-5 110 23 @ 10-5 0.9

-93 0.0032 30

-93 0.016 110 0.16 1.3

-87 0.04 150 0.3b N/A

-81 0.02 44

-81 0.07 140 0.5 1

-78 0.82 ca The reported concentration of 4b is calculated following the reaction of 1S and 1C.b A second order rate constant was calculated using the equation kobs1T/[4b].c Extrapolated rate constant used for the relative rates reported in Fig. 2 in the main body of thecommunication.

At -131 °C, 4b was injected (0.25 - 0.4 mL, 1.2 - 2.5 M) as a solution in 3:1 and 3:2 THF/Et2O (Fig. S-10). A higher concentration injection was not possible due to precipitation of 4b and sample freezing. Forthe same reasons, experiments with p-dimethylaminobenzaldehyde (4a) could not be performed at thistemperature. Whereas in the case of MeI, benzaldehyde, 2, and 4, the rate of disappearance of 1C wasconstant and determined by rate-limiting dissociation to 1S, the disappearance of 1C upon reaction with 4bwas inhibited by a factor of ca 100. Although the observed inverse first order dependance on 2b isinconclusive based upon the small change in [4b] for the two trials, the fact of the inhibition is striking andoutside of the range of normal error. When sample freezing becomes problematic a similar “apparent”inhibition can be observed, but in such cases 1S is affected as well and the plots of decay of 1S and 1C arehighly irregular. The immediate reaction of 1S, and the fairly regular first order decay of 1C leads us tobelieve freezing was not the issue in these experiments. Since we have observed a strong interaction between4b and 1T, it might also be expected that 4b interacts strongly with 1C, however a mechanistic investigationof this interaction was not pursued further.

S-14

Figure S-10. (a) 1H NMR spectra for the injection of p-diethylaminobenzaldehyde (0.25 mL, 2.5 M inTHF, 0.12 M in situ) into a solution of 1 (0.04 M) in 4 mL of 1:3 THF/Me2O at -131 °C and (b) raw plots ofdisappearance of 1C for two concentrations of 4b.

0 900 1800 2700 3600 4500 5400 6300t / s

0.0

5.0

10.0[1

C] /

mM

5b 1-H

LiOSiMe3

1H PhSiMe3t / s 1T

0.4 0.2 0.0 -0.2ppm

1C

1T1C 1SPhSiMe3 1-H

0

0.5

1.34.78.8

50.3

133.3329.9

946.5

1,563

2,1802,7964,030

5,2637,1138,962

10,81212,662

14,51216,362

18,211

20,06121,911

Me3Si

Me3SiMe3Si : // Li

+

4b

Me3Si

Me3SiMe3Si Li inhibited by

4b

Me3Si

Me3SiMe3Si

-130 °CLi

kobs1C = 0.04 s-1for reaction with MeI

[4b] = 45 mM

[4b] = 100 mM

kobs3C

H

Me3Si SiMe3

Et2N1

0.04 M1:3 THF/Me2O

[4a]0 = 0.12 M

kobs1C = 2.36 10-4 s-1

kobs1C = 4.57 10-4 s-1

1C 1S

5b

(a)

(b)

S-15

130 140 150 160 170 180 190 200T / K

10

11

12

13

14

ΔG

/ kc

al/m

ol

Me3Si

Me3SiLiCMe3Si

SiMe3

SiMe3

C SiMe3

Li+

k21T Ar H

Me3Si SiMe3

+ LiOSiMe3

ΔS = -16 cal/deg molΔH = 10.6 kcal/mol

ΔS = -10.5 cal/deg molΔH = 10.5 kcal/mol

ΔS = -16 cal/deg molΔH = 8.2 kcal/mol

5

2, 3, or 4b

CF3

F3C

F Et2N

Ar =2

3

4b

4b2 35c 5d 5b

Activation Parameters for the reaction of Aldehydes (2, 3, 4b) with 1T. Activation parameters weredetermined by converting second order rate constants (Tables S-1, S-2, S-4) to )G‡ using the equation:)G‡= 1.987*T*[23.76+ln(T/k)]. If the temperature of the variable concentration experiments differedslightly, an average temperature was used for the plot below (Fig. S-11).

Figure S-11. Eyring plot for the second order reactions of 1T with aldehydes 2, 3, 4b in 1:3 THF/Me2O.

S-16

1H RINMR Spectroscopy of the reaction of 1T with HMPA at -86 °C. HMPA (0.2 mL, 4.3 M inTHF) was injected into a solution of 1 (0.04 M) in 4 mL of 1:3 THF/Me2O (Fig. S-12). The rate determinedfor dissociation of 1T is shown on the Eyring plot of Fig. S-3. It is within error of that measured by theinjection of MeI..

Figure S-12. (a) 1H NMR spectra and (b) first order plot for the 0.2 mL injection of a 4.4 M THFsolution of HMPA (0.22 M in situ) into a 0.04 solution of 1 in 4 mL of 1:3 THF/Me2O at -86 °C.

Me3Si

Me3SiLiCMe3Si

0.22 M HMPA Me3Si

Me3SiC:--//Li+(HMPA)4Me3Si

1S-HMPA0.04 M 1

0 3000 6000 9000 12000 15000 18000t / s

0.0

0.5

1.0

1.5

2.0

ln([1

T]0/

[1T]

t)

0.2 0.0 -0.2ppm

1-H1T

1C 1S

PhSiMe3

1S-HMPA

0

0.5

2.53

18.8

181

1,403

2,904

4,406

5,907

7,409

8,910

1,913

14,917

t / s

1T

1H

k11T = 6.6 10-5 s-1

1:3 THF/Me2O, -86 °C

(a)

(b)

S-17

Me3Si

Me3SiLiMe3Si

SiMe3

SiMe3

SiMe3

Li+Me3Si

Me3SiMe3Si : // Li

+(HMPA)4k21T4a

HMPA

0 120 240 360 480 600t / s

0

5

10

15

20

25

Con

cent

ratio

n / m

M

kobs = 0.015 s-1

kobs1T-HMPA = 3.3 10-3 s-1

[4a] = 0.01 M

0.00 0.02 0.04 0.06[4a] / M

0.000

0.010

0.020

kobs

1T /

s-1

-4.8 -4.4 -4.0 -3.6 -3.2 -2.8ln ([4a])

-6.0

-5.0

ln (k

obs 1

T) n = 0.85

k21T = 0.23 M-1 s-1

[4a] = 0.06 M

(b)(a)

(c)

[1] = 0.06 M

T = -80 °C, 1:3 THF/Me2O

1H NMR Spectroscopy for the Reaction of 1T with p-Dimethylaminobenzaldehyde (4a) inTHF/Me2O/HMPA. The rate of 1T with 4a was determined by injecting 0.25 mL of a solution of 4a (0.22or 1.5 M) in HMPA (0.77 mL, 4.4 mmol) and THF (0.25 mL) into a solution of 1 (0.06 M) in 4 mL of 1:3THF/Me2O at -80 °C (in situ [HMPA] = 0.25 M and [4a] = 0.01 or 0.06 M). An order of 0.85 in 4a wasdetermined from a plot of ln[4a] vs ln[kobs1T] for two concentrations of aldehyde. A second order rate constant(k21T-4a) was determined from a plot of [4a] vs. kobs1T, and is within error of the rate of 1T in the absence ofHMPA (compare to data in Table S-3). Representative spectra are shown in Fig. 3 of the communication andplots of triple ion disappearance are shown in Fig. S-13.

Figure S-13. (a) Raw plots for the decay of triple ion after the injection of p-dimethylaminobenzaldehyde and HMPA (0.25 M in situ) into a solution of 1 in 4 mL of 1:3 THF/Me2O.Plots of (b) kobs1T vs. [4a] to determine a second order rate constant and of (c) ln[4a] vs ln(kobs1T) to determineorder in aldehyde.

S-18

2

5c

H

Me3Si SiMe3

+ LiOSiMe3

Me3Si

Me3SiC:- // +Li(HMPA)4Me3Si

0.027 M 1S-HMPA1:3 THF/Me2O CF3

F3C

0.4 0.2 0.0 -0.2 -0.4 -0.6ppm

1S-HMPA1-HPhSiMe3

x

0

0.8

1.6

2.4

t / s

LiOSiMe3

0.0 0.5 1.0 1.5t / s

0

10

20

30

40

[1S-

HM

PA

] / m

M

kobs1S-HMPA ≥ 2 s-1

5c

1-H

T = -131 °C

1H NMR Spectroscopy for the Reaction of 1S-HMPA with 3,5-Bis(trifluoromethyl)benzaldehyde(2). HMPA (0.13 mL, 0.075 mol) was added to an NMR sample of 1 (0.027 M) in 4 mL of 1:3 THF/Me2Oat -78 °C. A solution of 2 (0.1 mL, 2.5 M in 1:1 THF/Et2O) was injected by RINMR at -131 °C (Fig. S-14).The rate is too fast to measure.

Figure S-14. 1H NMR and plot of 1S-HMPA disappearance for the 0.1 mL injection of 2 (0.03 M in situ)into a solution of 1 (0.027 M) in 4 mL of 1:3 THF/Me2O with 6.3 equivalents of HMPA at -131 °C.

S-19

1H NMR Spectroscopy for the Reaction of 1S-HMPA with p-Fluorobenzaldehyde (3). HMPA (0.12mL, 0.072 mol) was added to an NMR sample of 1 (0.02 M) in 4 mL of 1:3 THF/Me2O at -78 °C. A solutionof 3 (0.1 mL, 1.87 M in 1:1 THF/Et2O) was injected by RINMR at -133 °C (Fig. S-15). The spectrometerwas not warmed during the injection so the experimental temperature is expected to be ca -132 °C.

Figure S-15. 1H NMR and plot of 1S-HMPA disappearance from the 0.1 mL injection of 3 (0.044 Min situ) into a solution of 1 (0.024 M) in 4 mL of 1:3 THF/Me2O with 6.6 equivalents of HMPA at ca -132°C.

0 60 120 180 240t / s

0

5

10

15

20

25

30

35

40

[1S-

HM

PA

] / m

M

kobs1S-HMPA = 0.012 s-1

T = -133 °C

0.3 0.2 0.1 0.0 -0.1 -0.2ppm

X

X

PhSiMe3 5d

1-H

1S-HMPA

1S-HMPA

LiOSiMe3

0

2.1

5.2

10.3

41.2

92.7

144.2

195.7

247.2

3

5d

H

Me3Si SiMe3

+ LiOSiMe3

F

Me3Si

Me3SiC:- // +Li(HMPA)4Me3Si

0.024 M 1S-HMPA1:3 THF/Me2O

1Ht / s

S-20

CMe3Si

Me3SiMe3Si

1:3 THF:Me2O-69 °C

H

Me3Si SiMe3

+ LiOSiMe3

1H

Et2N

t / s

Li

0.2 0.0 -0.2ppm

0

0.5

2.5

4.6

8.6

12.7

16.7

20.8

24.9

187.3

2,390

4,593

6,796

8,999

11,202

1T1C 1S

5b1-SePh

PhSiMe3LiOSiMe3

1S-HMPA

1-H

4b

5bHMPA

0.02 M 1

H

O

Et2N

1H RINMR Spectroscopy of the Reaction of 1S-HMPA with p-Diethylaminobenzaldehyde (4b) atVarious Temperatures. The rates of 1S-HMPA with 4b were determined either by injecting 4b into a pre-formed solution of 1S-HMPA, or by injecting a mixture of 4b and HMPA as a THF solution ([1] = 0.02 - 0.04M). Representative spectra for the latter method are shown in Fig. S-16. In such experiments, the triple ionis converted rapidly to 1S-HMPA at a rate (kobs1T = 0.011 s-1 at -84 °C and kobs1T = 0.08 s-1 at -69 °C) withinerror of that extrapolated for solutions in the absence of HMPA (compare to rates in Table S-4 and activationparameters in Figure S-11). An order in 4b of n = 0.8 was determined from a plot of ln[4b] vs ln[kobs1S-HMPA]at -58 °C, for two concentrations of 4b. We assume that is within error of being first order in aldehyde;deviation from 1 could result from the 1 degree temperature difference for the two trials). Second order rateconstants are calculated from the equation kobs1S / [4b] (Table S-5) and converted to )G‡ using the equation:)G‡= 1.987*T*[23.76+ln(T/k)] (Fig. S-17).

Figure S-16. 1H NMR spectra for the 0.25 mL injection of a 1.6 M HMPA solution of 4b (0.044 M 4and 0.24 M HMPA in situ) into a 0.02 M solution of 1 in 4 mL of 1:3 THF/Me2O at -69 °C.

S-21

Table S-5. Rate data for the reaction of 1S-HMPA and 4b.

T / °C kobs1S / s-1 [4b] / mM k21S-4b / M-1 s-1 n [HMPA] / mM

-84 7.3 @ 10-6 50 0.15 @ 10-3 n.d. 240

-69 70 @ 10-6 44 1.5 @ 10-3 n.d. 240

-58 3.5 @ 10-4 60 5.8 @ 10-3 230

-59 7.3 @ 10-4 150 4.9 @ 10-3 0.8 170

Figure S-17. Eyring plot for the second order reaction of 1S-HMPA and 4b.

185 190 195 200 205 210 215 220T / K

12.0

13.0

14.0

15.0

16.0

ΔG /

kcal

/mol

ΔS = -18 cal/deg molΔH = 10.9 kcal/mol

Me3Si

Me3SiMe3Si : k21S-HMPA

SiMe3Me3Si

H

+ Me3SiOLi(HMPA)n

4b

STD = 0.9952Et2N

Li+(HMPA)4

1S-HMPA 5b

S-22

S3. Competition Experiments

For two reactants (A and B) competing for a deficiency of the same reagent (C) (where both reactionshave the same order) the relative rates can be calculated using the formula kA/kB = ln (XA left)/ln (XB left).“XA left” and “XB left” are defined as the mole fractions of the two starting materials remaining at the endof the reaction relative to the amount of starting materials at the beginning of the reaction. For thesecompetitions, we sought to determine the specific relative reactivity of 1T with aldehydes. Since there is noway to thermodynamically prepare a solution of 1 that is 100% triple ion, we pre-treated the solution of 1 withMeI to selectively quench the monomers (1S and 1C). Triple ion dissociation is slow enough (t1/2 =36 min)that the aldehyde solution can be added before a significant amount of the monomers have been regenerated.

To a dry 5 mL long-neck round bottom flask equipped with stir bar and purged with N2 was added(Me3Si)3CSePh (0.12 g, 0.39 mmol) and 1 mL of THF. The reaction was cooled to -78 °C and 3 mL of Me2Owas added. n-BuLi (0.15 mL, 2.5 M in hexanes) was added to generate the lithium reagent 1. Theseconditions closely match those used in the NMR experiments so we can assume that roughly half of thereagent is in the monomeric form. In a separate flask a solution of two aldehydes is prepared (0.39 mmoleach in 0.3 mL THF). Half an equivalent of MeI (12 µL, 0.2 mmol) was added to the lithium solution at -78°C, and immediately after (< 60 s) the solution of the mixture of aldehydes was added. The reaction wasstirred for 20 mins and then warmed to room temperature, allowing the Me2O to evaporate. Water was added(2 mL) and the solution extracted with 5 mL Et2O. The organic layer was separated, dried with MgSO4 andconcentrated under low pressure. Product and remaining starting material ratios were determined byintegrating the aldehyde and vinyl protons. Relative rates of k3/k4a = 7 and 15 and k2/k3 = 3 were determined.

S-23

C LiMe3SiMe3Si

Me3Si

1

1 equiv. MeI

THF, -78 °C, 10 min.C MeMe3Si

Me3Si

Me3Si

1-Me66 %

S4. Syntheses

Tris(trimethylsilyl)phenylselenomethane (1-SePh). This compound was synthesized using a slightmodification of the procedure described by Sikorski.[S2] To an oven dried, 50 mL rb flask with stir bar wasadded 3.0 g (10.7 mmol) of tris(trimethylsilyl)methane (1-H). The flask was fitted with a septum, purgedwith N2, and 20 mL of THF and 10.0 mL (11.1 mmol) of 1.11 M MeLi in ether. The septum was greased andthe solution stored at r.t. for 3 days during which the methane was allowed to escape periodically by insertinga needle. After metallation was complete the flask containing a pale yellow clear solution was cooled to -78°C, and 3.5 g (11.1 mmol) of diphenyl diselenide in 5 mL of THF was added via cannula. The solution wasstirred for 20 min, and 1.0 mL (14.1 mmol) of acetyl chloride was added and the solution warmed to r.t. Thereaction was diluted with 100 mL of 1:1 ether/hexanes, washed with NaHCO3 (2 x 120 mL) and brine (1 x80 mL), dried over Na2SO4. Removal of the solvent by rotary evaporation yielded a clear pale yellow liquid.Purification of the crude product by preparatory TLC using hexanes as eluent (Rf = 0.5) yielded 3.80 g (9.82mmol, 92 %) of a clear yellow liquid which solidifies at refrigerator temperature (the literature reports amelting point of 4 oC[S5]). 1H NMR (300 MHz, CDCl3): * 0.20 (Si(CH3)3, s), 7.18-7.33 (3-Ph, m), 7.81-7.85(2-Ph, m). 13C NMR (75.4 MHz, CDCl3): * 3.57 (Si(CH3)3), 16.54 (CSi3Se), 128.22 (o-PhSe), 128.61(p-PhSe), 129.31 (i-PhSe), 138.45 (m-PhSe).

1,1,1-Tris(trimethylsilyl)ethane (1-Me). To an oven dried, N2 purged, 25 mL rb flask with stir bar, fittedwith a septum was added 12 mL of THF and 5.0 mL (1.0 mmol) of 0.2 M 1 in THF. The solution was cooledto -78 °C and 63 :L (1.0 mmol) of iodomethane was added. The reaction was stirred for 10 minutes at -78°C, and warmed to r.t. over 1 h. The reaction was diluted with 30 mL of 1:1 ether/hexanes, washed withwater(2 x 50 mL) and brine (1 x 30 mL), dried over Na2SO4. Removal of the solvent by rotary evaporationyielded a clear colorless liquid. Preparatory TLC of the crude product using hexanes as eluent (Rf = 0.44)yielded 180 mg (0.66 mmol, 66 %) of a clear colorless liquid. Note: There is no chromophore for thiscompound, so small bands were removed until the product was recovered. 1H NMR (300 MHz, CDCl3): *0.07 (Si(CH3)3, s), 1.07 (CH3, s). 13C NMR (75.4 MHz, CDCl3): * 0.99 (Si(CH3)3), 3.26 (CSi3), 13.81 (CH3).Mass Spec: M+ = 274.1649 (calc. for C11H30Si3 = 246.1655).

C HMe3SiMe3Si

Me3Si

1-H

1. MeLi, THF, 2-3 days

2. PhSeSePh, -78 °CC SMeMe3Si

Me3Si

Me3Si

1-SePh92 %

S-24

C LiMe3SiMe3Si

Me3Si

1

1 equiv. MeSSMe

THF, -78 °C, 10 min.C SMeMe3Si

Me3Si

Me3Si

1-SMe75 %

C LiMe3SiMe3Si

Me3Si

1

1 equiv. EtSSEt

THF, -78 °C, 10 min.C SEtMe3Si

Me3Si

Me3Si

1-SEt82 %

Ar

H

Me3Si

Me3Si

C LiMe3SiMe3Si

Me3Si1 5

THF, -78 °C

5aH

O

R

R = NMe25b R = NEt25d R = F5e R = H

Tris(trimethylsilyl)(methylthio)methane (1-SMe). To an oven dried, N2 purged, 25 mL rb flask withstir bar, fitted with a septum was added 12 mL of THF and 5.0 mL (1.0 mmol) of 0.2 M 1 in THF. Thesolution was cooled to -78 °C and 90 :L (1.0 mmol) of MeSSMe was added. The reaction was stirred for10 minutes at -78 °C, and warmed to r.t. over 1 h. The reaction was diluted with 30 mL of 1:1 ether/hexanes,washed with water(2 x 50 mL) and brine (1 x 30 mL), dried over Na2SO4. Removal of the solvent by rotaryevaporation yielded a clear colorless liquid. Preparatory TLC of the crude product using hexanes as eluent(Rf = 0.58) yielded 210 mg (0.75 mmol, 75 %) of a clear colorless liquid. 1H NMR (300 MHz, CDCl3): *0.20 (Si(CH3)3, s), 2.18 (CH3S, s). 13C NMR (75.4 MHz, CDCl3): * 0.99 (CSi3), 2.54 (Si(CH3)3), 17.97(SCH3). Mass Spec: M+ = 278.1371 (calc. for C11H30SSi3 = 278.1376).

Tris(trimethylsilyl)(ethylthio)methane (1-SEt). To an oven dried, N2 purged, 25 mL rb flask with stirbar, fitted with a septum was added 12 mL of THF and 5.0 mL (1.0 mmol) of 0.2 M 1 in THF. The solutionwas cooled to -78 °C and 123 :L (1.0 mmol) of EtSSEt was added. The reaction was stirred for 10 minutesat -78 °C, and warmed to r.t. over 1 h. The reaction was diluted with 30 mL of 1:1 ether/hexanes, washedwith water(2 x 50 mL) and brine (1 x 30 mL), dried over Na2SO4. Removal of the solvent by rotaryevaporation yielded a clear colorless liquid. Preparatory TLC of the crude product using hexanes as eluent(Rf = 0.58) yielded 204 mg (0.82 mmol, 82 %) of a clear colorless liquid. 1H NMR (300 MHz, CDCl3): *0.21 (Si(CH3)3, s), 1.16, (CH3, t), 2.67 (CH2S, q). 13C NMR (75.4 MHz, CDCl3): * 0.99 (CSi3), 2.57(Si(CH3)3), 14.00 (CH3), 27.63 (SCH2). Mass Spec: M+ = 292.1539 (calc. for C12H32SSi3 = 292.1532).

1,1-Bis(trimethylsilyl)-2-phenylethene (5e). To an oven dried, N2 purged, 25 mL rb flask with stir bar,fitted with a septum was added 12 mL of THF and 5.0 mL (1.0 mmol) of 0.2 M 1 in THF. The solution wascooled to -78 °C and 101.6 :L (0.98 mmol) of benzaldehyde was added. The reaction was stirred for 10 minat -78 °C, and warmed to r.t. over 1 h. The reaction was diluted with 30 mL of 1:1 ether/hexanes, washedwith water(2 x 50 mL) and brine (1 x 30 mL), dried over Na2SO4. Removal of the solvent by rotaryevaporation yielded a clear colorless liquid. Preparatory TLC of the crude product using hexanes as eluent(Rf = 0.78) yielded 175 mg (0.70 mmol, 70 %) of a clear colorless liquid. 1H NMR (300 MHz, CDCl3): *-0.05, 0.20 (Si(CH3)3, 2-s), 7.15-7.32 (Ph, m), 7.77 (CHPh, s). 13C NMR (75.4 MHz, CDCl3): * 0.56, 2.00(Si(CH3)3), 126.97, 127.73, 127.82 (o, m, p-Ph), 142.81 (i-Ph), 146.39 (CMe3Si2), 154.93 (PhHC=C). MassSpec: M+ = 248.1419 (calc. for C14H24Si2 = 248.1416).

1,1-Bis(trimethylsilyl)-2-(4-dimethylaminophenyl)ethene (5a). 1H NMR (300 MHz, CDCl3): * 0.04(s, 9H), 0.17 (s, 9H), 2.96 (s, 6H), 6.66 (d, J = 8.6 Hz, 2H), 7.12 (d, J = 8.4 Hz, 2H), 7.66 (s, 1H). 13C NMR (90.556 MHz, CDCl3): * 1.12 (CH3), 2.58 (CH3), 40.87 (CH3), 111.90 (CH), 127.73 (C),129.65(CH), 142.35 (C), 150.11 (C), 155.71 (CH). Mass Spec: [M+H]+ = 292.1916 (calc. for C16H30NSi2=292.1912).

S-25

Ar

H

Me3Si

Me3Si

C LiMe3SiMe3Si

Me3Si1 5c

THF, -78 °C

H

OCF3

CF3

1,1-Bis(trimethylsilyl)-2-(4-diethylaminophenyl)ethene (5b). 1H NMR (300 MHz, CDCl3): * 0.05 (s,9H), 0.16 (s, 9H), 1.15 (t, J = 7.1 Hz, 6H), 3.35 (q, J = 7.0 Hz, 4H), 6.59 (d, J = 8.8 Hz, 2H), 7.09 (d, J = 8.6Hz, 2H), 7.62 (s, 1H). 13C NMR (75.4 MHz, CDCl3): * 1.15 (CH3), 2.61 (CH3), 12.91 (CH3), 44.74 (CH2),111.31 (CH), 127.75 (C), 130.01 (CH), 141.23 (C), 147.48 (C), 155.81 (CH). Mass Spec: [M+H]+ = 320.2226(calc. for C18H34NSi2= 320.2225).

1,1-Bis(trimethylsilyl)-2-(4-fluorophenyl)ethene (5d). 1H NMR (300 MHz, CDCl3): * -0.050 (s, 9H),0.181 (s, 9H), 6.978 (t, J= 8.8 Hz, 2H), 7.13 (dd, J = 8.6, 5.4, 2H), 7.67 (s, 1H). 13C NMR (75.4 MHz,CDCl3): * -0.125 (CH3), 1.36 (CH3), 113.97 (CH, d, 2JCF = 21.2 Hz), 128.82 (CH, d, 3JCF = 8.0 Hz), 138.10(C), 138.15 (C), 146.44 (CH), 152.98 (C), 161.39 (CF, d, 1JCF=245.5 Hz). Mass Spec: M+= 266.1329 (calc.for C14H23FSi2= 266.1317).

1,1-Bis(trimethylsilyl)-2-(3,5-bis(trifluoromethyl)phenyl)ethene (5c). 1H NMR (300 MHz, CDCl3):* -0.05 (s, 9H), 0.21 (s, 9H), 7.6 (bs, 2H), 7.68 (s, 1H), 7.76 (bs, 1H). 13C NMR (75.4 MHz, CDCl3): * 0.70(CH3), 2.13 (CH3), 121.00 (CH, sept, 3JCF = 3.2 Hz), 123.72 (CF3, q, 1JCF = 272 Hz), 128.48 (CH, q, 3JCF = 1.8Hz), 131.48 (C, q, 2JCF = 32.6 Hz), 144.79 (C), 150.938 (CH), 152.45 (C). Mass Spec: M+ = 384.1152 (calc.for C16H22F6Si2 = 384.1159).

S5. References

[S1] Watson, S. C.; Eastham, J. F. J. Organomet. Chem. 1967, 9, 165-168. [S2] Sikorski, W. H.; Sanders, A. W.; Reich, H. J. Magn. Reson. Chem. 1998, 36, S118-S124.[S3] Yus, M.; Guijarro, A. Tetrahedron 1996, 52, 1797-1810.[S4] Jones, A. C.; Sanders, A. W.; Bevan, M. J.; Reich, H. J. J. Am. Chem. Soc. 2007, 129, 3492-3493.[S5] Bildstein, B.; Giselbrecht, K.; Sladky, F. Chem. Ber. 1989, 122, 2279-2281.