Facile Activation of Homoatomic σ Bonds in White Phosphorus and Diborane by a Diboraallene.

Metal-free activation of homoatomic E-E σ bonds (E=P, B) in white phosphorus (P4 ) and bis(catecholato)diboron (B2 cat2 ) with a 1,2-diboraallene 1 is reported. The 1:1 and 1:2 reactions of P4 with 1 afford Bn P4 cages (2: n=2, 3: n=4), whereas a stoichiometric mixture of 1 and B2 cat2 undergoes homonuclear catenation through the addition of the B-B σ bond of B2 cat2 across the B=B double bond of 1 (i.e. diboration), which leads to the formation of a tetraborane (4) featuring a B4 chain.