Structural diversity in multinuclear tantalum polyhydrides formed via reductive hydrogenolysis of metal-carbon bonds.

Using H2 as a reducing agent, we demonstrate controlled reduction of tri- and tetramethyl tantalum bis(N-heterocyclic carbene)borate complexes to yield low-valent, multinuclear tantalum polyhydrides. Reaction of a Ta(v)Me3 complex with H2 afforded a bimetallic, hydride-bridged Ta(iv) complex. The analogous reaction of a Ta(v)Me4 complex in benzene or toluene yielded bimetallic Ta(iii) complexes in which both metals are bound to the same face of a μ-η4:η4-arene2- ligand.