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 (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 B n P 4 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 σ 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.