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Abstract:
The reaction of a toluene solution of PhNC(Ph)NHPh
(N,N'-diphenylbenzamidine) with n-butyllithium gave the toluene-solvated
amidinolithium compound {Li[PhNC(Ph)NPh]}n. Similarly the same
reaction performed in the presence of the Lewis-base donors
(Me2N)3PO (hmpa), Me2N(CH2)2NMe2 (tmen) or
[Me2N(CH2)2]2 (pmdien) yielded the am{Li[PhNC(Ph)NPh·hmpa]}2 2, {Li[PhNC(Ph)NPh]·tmen} 3 and
{Li[PhNC(Ph)NPh]. pmdien} 4 respectively. In addition the reaction of a
toluene solution of the related amidine
PhNC(Me)NHPh (N,N′-diphenylacetamidine) with LiBu in the presence of
hmpa afforded {Li[PhNC(Me)NPh]·hmpa}2 5. The solid-state structures
of 2-5, which have been resolved by single-crystal X-ray diffraction
methods, show both similarities and differences The complexes 3 and 4,
which contain the di- and tri-dentate ligands tmen and pmdien
respectively, are monomeric, whilst use of the unidentate Lewis base
hmpa results in dimers 2 and 5. However, the way in which dimerisation
is achieved differs. The co-ordination geometry about the lithium cation
is clearly influenced by the choice of donor and as such shows how
change in the denticity of the donor ligand utilised can have a
significant effect on the solid-state structure of the system.
