Hyperfine Coupling Constants and Covalency in Sandwich Complexes

摘要

An analysis of the isotropic proton hyperfine coupling constants of V(C5H5)2, Ni(C5H5)2, and Cr(C6H6)2plus;is given. The unpaired electrons in thee1g*molecular orbitals in Ni(C5H5)2are found to be rather strongly delocalized into the carbon2pzndash;pgr;framework of the ligands. In agreement with bonding theories this indicates that the interaction between the metal3dxzand3dyzorbitals and the ligande1gndash;pgr;molecular orbitals is very important for the chemical bonding in sandwich complexes. In Cr(C6H6)2plus;and V(C5H5)2the proton coupling constants are determined mainly bysgr;delocalization of the unpaired electron in thea1glpar;3dz2rpar;orbital into the hydrogen1sorbitals. In V(C5H5)2, also, delocalization into the ligandpgr;framework is present and this is thought to be due to thee2gorbitals. It is concluded that the interaction of the metal3dxyand3dx2minus;y2orbitals with the ligande2gndash;pgr;molecular orbitals is appreciable.