(Trimethylsilyl)methyllithium

Chemical compound From Wikipedia, the free encyclopedia

(Trimethylsilyl)methyllithium is classified both as an organolithium compound and an organosilicon compound. It has the empirical formula LiCH2Si(CH3)3, often abbreviated LiCH2TMS. It crystallizes as the hexagonal prismatic hexamer [LiCH2TMS]6, akin to some polymorphs of methyllithium.[2] Many adducts have been characterized including the diethyl ether complexed cubane [Li4(μ3-CH2TMS)4(Et2O)2][3] and [Li2(μ-CH2TMS)2(TMEDA)2].[4]

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(Trimethylsilyl)methyllithium
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.157.622 Edit this at Wikidata
EC Number
  • 629-440-7
  • InChI=1S/C4H11Si.Li/c1-5(2,3)4;/h1H2,2-4H3;/q-1;+1
    Key: KVWLUDFGXDFFON-UHFFFAOYSA-N
  • [Li+].C[Si](C)(C)[CH2-]
Properties
C4H11LiSi
Molar mass 94.16 g·mol−1
Appearance white or colorless solid
Density 0.937 g/cm3
Hazards
GHS labelling:[1]
GHS02: FlammableGHS05: Corrosive
Danger
H225, H314
P210, P233, P240, P241, P242, P243, P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P370+P378, P403+P235, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 Â°C [77 Â°F], 100 kPa).
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Preparation

(Trimethylsilyl)methyllithium, which is commercially available as a THF solution, is usually prepared by treatment of (trimethylsilyl)methyl chloride with butyllithium:[5]

(CH3)3SiCH2Cl + BuLi → (CH3)3SiCH2Li + BuCl

(Trimethylsilyl)methylmagnesium chloride is often functionally equivalent to (trimethylsilyl)methyllithium. It is prepared by the Grignard reaction of (trimethylsilyl)methyl chloride.[6][7]

Use in methylenations

In one example of the Peterson olefination, (trimethylsilyl)methyllithium reacts with aldehydes and ketones to give the terminal alkene (R1 = Me, R2 & R3 = H):

The Peterson olefination

Metal derivatives

Structure of the organoscandium complex with two (trimethylsilyl)methyl ligands, (C5H5)Sc(CH2TMS)2(THF).[8] Color scheme: O (red), Sc (blue), Si (orange).

(Trimethylsilyl)methyllithium is widely used in organotransition metal chemistry to affix (trimethylsilyl)methyl ligands. Such complexes are usually produced by salt metathesis involving metal chlorides. These compounds are often highly soluble in nonpolar organic solvents, enjoying stability due to their steric bulk and resistance to beta-hydride elimination. In these regards, (trimethylsilyl)methyl is akin to neopentyl.

Bis(trimethylsilyl)methylmagnesium is used as an alternative to (trimethylsilyl)methyllithium.[9]

Related compounds

  • bis(trimethylsilyl)methyllithium[10]
  • tris(trimethylsilyl)methyllithium[11]

References

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