No 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) 1. Similarly the same reaction performed in the presence of the Lewis-base donors (Me(2)N)(3)PO (hmpa), Me(2)N(CH2)(2)NMe(2) (tmen) or [Me(2)N(CH2)(2)](2)NMe (pmdien) yielded the amidinolithium complexes {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(II) 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

An investigation of the lithiation and CS2-insertion reactions of R1R2CH2 precursors (reactions used in the syntheses of ketene dithioacetals) leads to the crystal structure determination of the monolithiated complexes R1R2CHCS2Li.TMEDA, 3 (R1 = Ph, R2 = pyridyl) and 4 (R1 = H, R2 = 2-methylpyrazine); attempted second lithiation of 3 fails to give the RlRZC=CS2Li2 species anticipated in the mechanism of reactions of this type, but synthetic and 1H NMR spectroscopic evidence indicates that 4 can be lithiated further.

n-Butyllithium reacts with a solution of PhNC(Ph)NHPh (N,N'-diphenylbenzamidine) and NMe[(CH,),NMe,], (pmdeta) to give the complex LiCPh(NPh),*pmdeta, which is monomeric in the solid state with a five-co-ordinate lithium cation bound to a tridentate pmdeta ligand and a bidentate amidinide anion (diazaallyl system, chelating), in which the two N-C bond lengths of 1.336(4) and 1.335(4) A suggest almost uniform delocalisation along the N-C -N unit.

Chiral [(salen)Li2-hmpal2 has a Li404 cubane-type core in the solid but low-temperature NMR spectroscopy reveals a racemisation equilibrium in solution; deliberate addition of H20 to [(salen)Li2], in the presence of tmen produces a species having two Li404 cubes sharing a common oxygen and containing tmen ligands acting in a hitherto unobserved monofunctional mode.