μ- and μ4–η2 coordination of A2H2 (A = C, Si, Ge, Sn and Pb) ligands with transition metals

The heavier analogs of C2H2 have been studied at the B3LYP level for their μ and μ4–η2 coordination properties with the transition metals. Based on known alkyne compounds, transition metal fragments [W2(μ-NH)(Cp)2(Cl)2] and [Fe4(CO)12] have been chosen. The SBKJC relativistic effective core potentials and their associated basis sets were used on W, Fe, Sn and Pb, and the 6-31G(d) basis set was used on all other elements. All the complexes of Si2H2, Ge2H2, Sn2H2 and Pb2H2 are found to be local minima. The trans-twist nature of the ligand A2H2 (A = Si–Pb) is large in μ-coordinated complexes of W, and it is very small in μ4–η2 coordinated complexes of Fe. The electronic structure of these complexes was investigated using fragment molecular orbital method (FMO).