Benzyl(trimethylsilyl)amidolithium: Structural studies by ab initio MO and X-ray crystallographic methods, and comparison with the known structures of dibenzyl and bis(trimethylsilyl) analogues

D R Armstrong, D R Baker, F J Craig, Robert Mulvey, W Clegg, L Horsburgh

Research output: Contribution to journalArticle

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Abstract

Prompted by its excellent nucleophilic properties in organic synthesis, benzyl(trimethylsilyl)amidolithium, a new commercial lithium amide reagent, has been subjected to a detailed structural study. X-ray crystallographic studies have revealed that in the absence of solvent ligands, it is trimeric with a classical, shield-shaped N3Li3 ring core, the amido substituents of which are organized in a cisoid manner. Solvation by hexamethylphosphoramide causes it to break down to a dimer, having a familiar lozenge-shaped N2Li2 ring core. These structures are compared with previously reported dibenzylamidolithium and bis(trimethylsilyl)amidolithium analogues. Primarily with a view to shedding further light on the role of Li ... benzyl interactions in these structures, ab initio MO geometry optimizations have been carried out on model monomeric fragments. Short Li ... C (benzyl) contacts observed in the crystal structure of benzyl(trimethylsilyl)amidolithium are retained in the theoretical monomer, although their presence appears to be dictated more by steric factors than by electronic deficiencies of the Li-delta+ centre. Copyright (C) 1996 Elsevier Science Ltd

LanguageEnglish
Pages3533-3542
Number of pages10
JournalPolyhedron
Volume15
Issue number20
DOIs
Publication statusPublished - 1996

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Hempa
Solvation
Lithium
Amides
Dimers
Monomers
Crystal structure
Ligands
analogs
X rays
Geometry
rings
amides
solvation
reagents
x rays
monomers
lithium
breakdown
dimers

Keywords

  • lithium n-benzyltrimethylsiylamide
  • molecular orbital methods
  • crystal structures
  • conjugate addition
  • trimeric dibenzylamidolithium
  • diethyl ether
  • basis sets
  • complexes

Cite this

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title = "Benzyl(trimethylsilyl)amidolithium: Structural studies by ab initio MO and X-ray crystallographic methods, and comparison with the known structures of dibenzyl and bis(trimethylsilyl) analogues",
abstract = "Prompted by its excellent nucleophilic properties in organic synthesis, benzyl(trimethylsilyl)amidolithium, a new commercial lithium amide reagent, has been subjected to a detailed structural study. X-ray crystallographic studies have revealed that in the absence of solvent ligands, it is trimeric with a classical, shield-shaped N3Li3 ring core, the amido substituents of which are organized in a cisoid manner. Solvation by hexamethylphosphoramide causes it to break down to a dimer, having a familiar lozenge-shaped N2Li2 ring core. These structures are compared with previously reported dibenzylamidolithium and bis(trimethylsilyl)amidolithium analogues. Primarily with a view to shedding further light on the role of Li ... benzyl interactions in these structures, ab initio MO geometry optimizations have been carried out on model monomeric fragments. Short Li ... C (benzyl) contacts observed in the crystal structure of benzyl(trimethylsilyl)amidolithium are retained in the theoretical monomer, although their presence appears to be dictated more by steric factors than by electronic deficiencies of the Li-delta+ centre. Copyright (C) 1996 Elsevier Science Ltd",
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author = "Armstrong, {D R} and Baker, {D R} and Craig, {F J} and Robert Mulvey and W Clegg and L Horsburgh",
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Benzyl(trimethylsilyl)amidolithium: Structural studies by ab initio MO and X-ray crystallographic methods, and comparison with the known structures of dibenzyl and bis(trimethylsilyl) analogues. / Armstrong, D R ; Baker, D R ; Craig, F J ; Mulvey, Robert; Clegg, W ; Horsburgh, L .

In: Polyhedron, Vol. 15, No. 20, 1996, p. 3533-3542.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Benzyl(trimethylsilyl)amidolithium: Structural studies by ab initio MO and X-ray crystallographic methods, and comparison with the known structures of dibenzyl and bis(trimethylsilyl) analogues

AU - Armstrong, D R

AU - Baker, D R

AU - Craig, F J

AU - Mulvey, Robert

AU - Clegg, W

AU - Horsburgh, L

PY - 1996

Y1 - 1996

N2 - Prompted by its excellent nucleophilic properties in organic synthesis, benzyl(trimethylsilyl)amidolithium, a new commercial lithium amide reagent, has been subjected to a detailed structural study. X-ray crystallographic studies have revealed that in the absence of solvent ligands, it is trimeric with a classical, shield-shaped N3Li3 ring core, the amido substituents of which are organized in a cisoid manner. Solvation by hexamethylphosphoramide causes it to break down to a dimer, having a familiar lozenge-shaped N2Li2 ring core. These structures are compared with previously reported dibenzylamidolithium and bis(trimethylsilyl)amidolithium analogues. Primarily with a view to shedding further light on the role of Li ... benzyl interactions in these structures, ab initio MO geometry optimizations have been carried out on model monomeric fragments. Short Li ... C (benzyl) contacts observed in the crystal structure of benzyl(trimethylsilyl)amidolithium are retained in the theoretical monomer, although their presence appears to be dictated more by steric factors than by electronic deficiencies of the Li-delta+ centre. Copyright (C) 1996 Elsevier Science Ltd

AB - Prompted by its excellent nucleophilic properties in organic synthesis, benzyl(trimethylsilyl)amidolithium, a new commercial lithium amide reagent, has been subjected to a detailed structural study. X-ray crystallographic studies have revealed that in the absence of solvent ligands, it is trimeric with a classical, shield-shaped N3Li3 ring core, the amido substituents of which are organized in a cisoid manner. Solvation by hexamethylphosphoramide causes it to break down to a dimer, having a familiar lozenge-shaped N2Li2 ring core. These structures are compared with previously reported dibenzylamidolithium and bis(trimethylsilyl)amidolithium analogues. Primarily with a view to shedding further light on the role of Li ... benzyl interactions in these structures, ab initio MO geometry optimizations have been carried out on model monomeric fragments. Short Li ... C (benzyl) contacts observed in the crystal structure of benzyl(trimethylsilyl)amidolithium are retained in the theoretical monomer, although their presence appears to be dictated more by steric factors than by electronic deficiencies of the Li-delta+ centre. Copyright (C) 1996 Elsevier Science Ltd

KW - lithium n-benzyltrimethylsiylamide

KW - molecular orbital methods

KW - crystal structures

KW - conjugate addition

KW - trimeric dibenzylamidolithium

KW - diethyl ether

KW - basis sets

KW - complexes

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T2 - Polyhedron

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