THEORETICAL-STUDY OF CONFORMATIONS OF SOME HETEROCYCLIC NICKEL SANDWICH COMPLEXES

The conformations of heterocyclic sandwich nickel complexes involving four-membered ring (eta-4-C2H3BSSiH2)2Ni, five-membered ring (eta-5-C4H5BSiH2)2Ni, six-membered ring (eta-6-C4H4B2F2)2Ni, and some polyheterocyclic rings have been studied by use of extended Huckel methods. The calculated results agree with those from experiment. Our objective was to identify the key orbitals for the observed dihedral angles. The general pattern that emerged was that the nickel valence electron pair (d(xz), d(yz)), favors the 90-degrees conformation, for it allows the pair to interact equally with the ring orbitals.