Density functional theory calculations have been performed for the terminal borylene, alylene, and gallylene complexes [(eta(5)-C5H5)(CO)(3)M(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 [(eta(5)-C5H5)(CO)(3)V-{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 pi-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 [(eta(5)-C5H5)(CO)(3)M(ENR2)] arise mainly from M <- ENR2 sigma donation. The pi-bonding contribution is, in all complexes, much smaller. The contributions of the electrostatic interactions Delta E-elstat are significantly larger in all borylene, alylene, and gallylene complexes than the covalent bonding Delta E-orb; that is, the M-ENR2 bonding in the complexes has a greater degree of ionic character.