Rhodium and ruthenium tetracarboxylate nitrosyl complexes: Electronic structure and metal-metal bond

electronic structure of the tetracarboxylates M2(mu-O2CH)(4), M-2(mu-O2CH)(4)(L)(2) (M = Ru, Rh; L = H2O, NO) was analyzed by the density functional theory with full Geometry optimization. The inclusion of nitrogen oxide orbitals into the molecular orbitals forming the metal-metal bond affects all of the main characteristics of this bond and the concomitant properties. In the case ofrhodium tetracarboxylates, one can consider destruction of the Rh-Rh covalent sigma-bond and reorientation of two electrons from the internal region of the Rh-2(mu-O2CH)(4) core to the outside, toward the axial ligands to give Rh-N covalent bonds. The axial coordination of nitrogen oxide in Ru-2(mu-O2CR)(4) is accompanied by destruction of the metal-metal TE-bond.