Infrared photodissociation spectroscopy of heteronuclear group 15 metal-iron carbonyl cluster anions AmFe(CO)n- (A = Sb, Bi; m, n = 2, 3).

Heteronuclear group 15 metal-iron carbonyl cluster complexes of AmFe(CO)n- (A = Sb, Bi; m, n = 2-3) were generated in the gas phase and studied by infrared photodissociation spectroscopy in the carbonyl stretching region. Their structures were determined by comparing the experimental spectra with predicted spectra derived from DFT calculations at the B3LYP and BP86 levels. All of the AmFe(CO)n- cluster anions were determined to have Fe(CO)n- fragments with all of the CO ligands terminally bonded to the iron center, and they can be regarded as being formed via the interactions of the neutral group 15 metal clusters with the Fe(CO)n- fragments. Bonding analyses indicated that each A2Fe(CO)n- (n = 2, 3) cluster anion contained two A-Fe single bonds and one A-A double bond. Each A3Fe(CO)n- (n = 2, 3) cluster anion involved three A-Fe single bonds and three A-A single bonds. There is an isolobal relationship between the Fe(CO)3- group and the group 15 atoms. The substitution of an Fe(CO)3- group in place of one A atom in the tetrahedral A4 molecule resulted in an A3Fe(CO)3- cluster anion with the closed-shell electronic configuration for all the group 15 metals and iron atoms.