Hybrid π Orbitals and Partial Double Bond Character in Covalent Complexes

Abstract

Angular parts of p‐ and d‐orbitals are hybridized to form a set of tetrahedrally oriented π orbitals. These orbitals are suitable for explaining partial double bond character in compounds such as nickel tetracarbonyl. It is shown that up to three of these orbitals may exist, each possessing the required properties of orthogonality and linear independence. The maximum partial double bond character allowed is, in this way, 75%. The strength of these orbitals, according to a modified Pauling's criterion, is discussed. Also the cases of trigonal bipyramidal and octahedral symmetry are discussed. An attempt is made to interprete semiquantitatively bond lengths in Cr, Fe, and Ni carbonyls.