A COMPARATIVE-STUDY OF THE BOND STRENGTHS OF THE 2ND ROW TRANSITION-METAL HYDRIDES, FLUORIDES, AND CHLORIDES

Correlated calculations have been performed for the diatomic second ro w transition metal hydrides, fluorides, and chlorides. The ground stat es have been determined for the entire second row from yttrium to pall adium. It is found that the halide binding energies vary much more acr oss the row than the hydride binding energies. The results are analyze d in terms of ionic and covalent contributions to the bonding. The two main factors responsible for the large variation of the halide bindin g energies are differences in ionization energies and differences in t he interactions between the halide lone-pairs and the metal 4d-orbital s for the atoms to the left and to the right. To the left the lone-pai r interaction is attractive through electron donation to empty 4d-orbi tals, whereas to the right the interaction is repulsive.