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

Metal-free activation of homoatomic E-E sigma bonds (E = P, B) in white phosphorus (P-4) and bis(catecholato)diboron (B(2)cat(2)) with a 1,2-diboraallene 1 is reported. The 1:1 and 1:2 reactions of P-4 with 1 afford BnP4 cages (2: n = 2, 3: n = 4), whereas a stoichiometric mixture of 1 and B(2)cat(2) undergoes homonuclear catenation through the addition of the B-B sigma bond of B-2 cat (2) across the B=B double bond of 1 (i.e. diboration), which leads to the formation of a tetraborane (4) featuring a B-4 chain.