Nature of bonding in terminal borylene, alylene, and gallylene complexes of vanadium and niobium [(η⁵-C<inf>5</inf>H<inf>5</inf>)(CO) <inf>3</inf>M(ENR<inf>2</inf>)] (M = V, Nb; E = B, Al, Ga; R = CH<inf>3</inf>, SiH<inf>3</inf>, CMe<inf>3</inf>, SiMe<inf>3</inf>): A DFT study

Density functional theory calculations have been performed for the terminal borylene, alylene, and gallylene complexes [(η5-C 5H5)(CO)3M(ENR2)] (M = V, Nb; E = B, Al, Ga; R = CH3, SiH3, CMe3, SiMe3) using the exchange correlation functional BP86. The calculated geometry parameters of vanadium borylene complex [(η5-C5H 5)(CO)3V{BN(SiMe3)2}] are in excellent agreement with their available experimental values. The M-B bonds in the borylene complexes have partial M-B double-bond character, and the B-N bonds are nearly B≡N double bonds. On the other hand, the M-E bonds in the studied metal alylene and gallylene complexes represent M-E single bonds with a very small M-E π-orbital contribution, and the Al-N and Ga-N bonds in the complexes have partial double-bond character. The orbital interactions between metal and ENR2 in [(η5-C5H 5)(CO)3M(ENR2)] arise mainly from M ↔ ENR2 σ donation. The π-bonding contribution is, in all complexes, much smaller. The contributions of the electrostatic interactions δEelstat are significantly larger in all borylene, alylene, and gallylene complexes than the covalent bonding δEorb; that is, the M-ENR2 bonding in the complexes has a greater degree of ionic character. © 2010 American Chemical Society.