Molecular Models of Solid State Metal Boride Structures

Based on existing connections between borane cages and boron-rich metal borides on the one hand and metal clusters containing boron atoms and metal-rich borides on the other, selected metallaboranes of intermediate stoichiometry are investigated as models for transition metal borides with similar M/B ratios. This study is possible due to the recent development of a general route to metallaboranes for group 5–9 metals that permits the distinct role of the transition metal in metallaborane cluster bonding to be revealed. The comparison shows that it is MM and MB covalent bonding rather than M and B electronic charges that drives change in structure with metal identity.