Aluminium amides derived from metallation of N,N'-di-tert-butylethylenediamine

The metallation of N,N'-dirtert-butylethylenediamine by AlH3 . NMe(3) has been investigated and shown to proceed via the formation of the unstable secondary amine-stabilised amidoalane [AlH2(Bu(t)NCH(2)CH(2)NBu(t)H)]. This compound reacted with an additional equivalent of AlH3 . NMe(3) to yield the the dibridging amidoalane complex [(AlH)(2){mu-N(Bu(t))CH2CH2N(Bu(t))}] or a molecule of the diamine to give the triamidoaluminium species [Al(Bu(t)NCH(2)CH(2)NBu(t))(Bu(t)NCH(2)CH(2)NBu(t)H)]. In the absence of an excess of AlH3 . NMe(3) or N,N'-di-tert-butjrlethylenediamine, [AlH3(Bu(t)NCH(2)CH(2)NBu(t)H)] eliminates molecular hydrogen to give the trans isomer of the dimeric diamidoalane complex trans-[{AlH[mu-N(Bu(t))CH(2)CH(2)NBu(t)]}(2)] Which is stable toward reaction with either of the reactants. A stable analogue of the intermediate [AlH2(Bu(t)NCH(2)CH(2)NBu(t)H)] was made by replacing a hydride by a chloride, achieved by using AlH2C . NMe(3) as the metallating agent. The cis isomer of the dimeric diamidoalane cis-[AlH{[mu-N(Bu(t))CH(2)CH(2)NBu(t)]}(2)] was prepared from the unstable lithium diamido aluminium hydride species [{Li[N(Bu(t))CH(2)CH(2)NBu(t)]AlH2}(n)] via elimination of lithium hydride. The aluminium triamide and the cis and trans isomers of the dimeric aluminium diamide have been structurally authenticated.