[1] They have the formula LnM-BR2 or LnM-(BR2LB) (L = ligand, R = H, organic substituent, LB = Lewis base).
[2] Such compounds, especially those derived from catecholborane and the related pinacolborane, are intermediates in transition metal-catalyzed borylation reactions.
Both B-H and B-B bonds add to low-valent metal complexes.
For example, catecholborane oxidatively adds to Pt(0) to give the boryl hydride.
[4] Addition of diboron tetrafluoride to Vaska's complex gives the triboryl iridium(III) derivative: