Homogeneous transition metal catalysed hydroboration reactions are discussed briefly, providing the background which led to the recent discovery of metal catalysed diborations [additions of the B-B bond in B-2(OR)(4) compounds] of alkynes, alkenes, 1,3-diynes, 1,3-dienes, and alpha,beta-unsaturated ketones. Catalysed additions of B-Si and B-Sn bonds are also presented. Metal catalysed synthesis of organoboron compounds is a useful new synthetic method.