Mono(borane)phosphides as ligands to lithium and aluminum

The complexation potential of mono(borane)diorganophosphides toward lithium and aluminum has been explored in the complexes [{(tmeda)Li}{P(BH3)Me-2}] (1), [{((-)-sparteine)-Li}{P*(BH3)(Ph)tBu}] (2), [(tmeda)(2)Li](+)[Al{P(BH3)Me-2}(4)](-) (3), and [(mtbe)Li](+)[Al{P(BH3)Me-2}(4)](-)(4) (tmeda = N,N,N',N'-tetramethylethylenediamine; mtbe = methyl-tert-butyl ether). In 1 there is competing Li-P and Li-H-B bonding, while in 2 Li-P coordination is absent due to steric hindrance. Compound 2 contains the enantiomerically pure P-chiral anion [P*(BH3)(Ph)tBu](-), which is a valuable building block for the synthesis of P-chirogenic phosphines. The complexes 3 and 4 are the first homoleptic tetraphosphorus aluminates to be structurally characterized.