A recently developed extension of the CNDO-method (Freund and Hohlneicher, 1979) is used to study the electronic structure of a no. of binuclear transition metal carbonyls and carboxylates with 4-fold or quasi-4-fold symmetry. The results are compared to those available from nonempirical calcns. Special attention is paid to the nature of the metal-metal bond. Connections with qual. MO-considerations allow a fairly general discussion of metal-metal bonding in binuclear transition metal complexes with basic 4-fold symmetry. A few, up to now unknown, but possibly existing, complexes are considered.