Synthesis, characterisation and a theoretical investigation of the formation of lithium dialkylaluminium amides

Clegg, W and Liddle, S T and Henderson, K W and Keenan, F E and Kennedy, A R and McKeown, A E and Mulvey, R E (1999) Synthesis, characterisation and a theoretical investigation of the formation of lithium dialkylaluminium amides. Journal of Organometallic Chemistry, 572 (2). pp. 283-289. ISSN 0022-328X

Abstract

Reaction of the pre-formed crystalline amides [(PhCH2)(2)NLi] and [Me2AlN(CH2Ph)(2)] in the presence of pyridine results in the formation of the mixed metal complex [Me2Al{(PhCH2)(2)N}(2)Li . pyr] 1. Ab initio molecular orbital calculations indicate formation of the bimetallic product is energetically favourable. Using single crystal X-ray analysis for 1 and the pyridine solvate [{(PhCH2)(2)NLi . pyr}(2)] 7, in combination with theoretical calculations, the possible driving forces for the reaction are discussed. A major contributing factor in the stabilisation of the bimetallic compound was found to be a reduction in steric crowding in the mixed metal base compared to the homometallic dialkylaluminium amide. In addition, complex 1 shows significant benzyl to lithium interactions which contribute to the overall bonding. Such interactions are unusual in that donor solvent is present as competing complexant.

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