Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3- (A=As, Sb, Bi) Complexes.

Heteronuclear transition-metal-main-group-element carbonyl complexes of AsFe(CO)3- , SbFe(CO)3- , and BiFe(CO)3- were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass-selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)3- . Chemical bonding analyses on the whole series of AFe(CO)3- (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp-p) type of transition-metal-main-group-element multiple bonding. The σ-type three-orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)3- (A=As, Sb, Bi) complexes.