BORON ATOMS IN TRANSITION-METAL CLUSTERS

The chapter surveys the methods of synthesis, the solution and solid-state structural properties, and the reactivity of transition metal cluster compounds, containing small borane fragments or single (naked) boron atoms. One significant feature of the coordination mode of the B2H6 group to a dimetallic fragment is the tendency toward an ethane like structure in contrast to the doubly hydrogen-bridged structure present in free diborane. Metallo borane cluster chemistry continues to be dominated by boron-rich systems. By virtue of the electron-deficient nature of the boron atom, its environment in a cluster and its reactivity therein may differ quite dramatically from that of—for example—another first row atom in a structurally related cluster molecule. The major isomer is proposed to have a structure equivalent to that in the solid state, and the minor one exhibits a symmetrically bound B and ligand with two terminal B–H and four bridging Ta– H–B interactions. © 1991, Elsevier Inc. All rights reserved.