Contributions to the chemistry of phosphorus .240. On the reactive behaviour of diphosphane-borane, P2H4 center dot BH3

Under mild temperature conditions, the thermal decomposition of diphosphane-borane (1) gives rise to the formation of phosphane-borane, PH3 . BH3, and triphosphane-2-borane, PH2-PH(BH3)-PH2 (2). In the presence of diphosphane-1,2-bis(borane), triphosphane-1,3-bis(borane), BH3-PH2-PH-PH2-BH3 (3), is formed additionally. The thermolysis product at room temperature is a polymeric solid of varying composition which contains phosphorus, boron, and hydrogen. Compound 1 reacts with metalating agents such as n-BuLi, LiBH4, and NaBH4 to furnish the borane-trihydrogendiphosphide ion, [PH2-PH-BH3](-), which immediately disproportionates to give the corresponding mono- and triphosphane derivatives. In the presence of an excess of THF-borane and in the case of a 1:1 molar ratio of 1:NaBH4, the disproportionation does not occur and the new diphosphide derivative sodium-1,1,2-tris(borane)-1,2,2-trihydrogendiphosphide, Na[(BH3)(2)PH-PH2BH3] (4) can be obtained. The action of additional NaBH4 yields the diphosphide dianion with four coordinated BH3 groups.