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.