M.O. description of diatomic molecules containing a transition group atom

Abstract

The M.O. configurations of diatomic molecules MX, where M contains a partly filled 3d shell, can be related to the more usual ligand field theory. In the same way as the 3d shell of gaseous atoms generally needs one or two 4s electrons for stabilizing the ground-state, certain molecules MX can be shown to contain the number of d-like electrons characterizing M(II) and an additional σ-electron. Comparisons are made with the occurrence of metallic bonding and 5d electrons in lanthanide compounds. Some molecules, such as TiO, pose unanswered questions, and much more experimental work would be desirable.