Solid state structures of homo- and hetero-bimetallic alkali metal complexes containing the dianion of (S)-N-(α-methylbenzyl)-allylamine

Dilithiation of the chiral amine (S)-N-(alpha-methylbenzyl) allylamine in the absence of a coordinating Lewis donor results in formation of crystals of a cyclic hexamer, {[(S)-alpha-(PhC(H)Me)(CH2CH=CHLi)N]Li}(6), 1, (rhombohedral, R3) while the addition of tmeda (N, N, N', N'-tetramethylethylenediamine) leads to deaggregation and formation of the dimer, {[(S)-alpha-(PhC(H)Me)(CH2CH=CHLi)N]Li.(tmeda)(2)}(2), 2 (monoclinic, P2(1)). Reaction with (BuLi)-Bu-II followed by (BuNa)-Bu-II leads to crystals of a cyclic mixed metal tetramer coordinated with thf, {[(S)-alpha-(PhC(H)Me)(CH2CH=CHNa)N]Li.(thf)}(4), 3 (orthorhombic, P2(1)2(1)2(1)). The three bimetallic complexes have been characterised by single crystal X-ray diffraction, NMR and elemental analysis. The allyl moieties in all three complexes retain the bonding pattern expected in an N-allylamine (-N(M)-CH2-C(H)=C(H)M', M=Li, M'=Li or Na) rather than forming a delocalised dianion or an enamide. The anionic amido N and the terminal vinylic C centres form multiple short bonds to all metal centres which in turn form short interactions with all atoms in the allyl groups, and in 1 with the closest Ph carbons.