Theoretical insights into M–SO bonds in transition metal-sulfur monoxide complexes [{N(SPMe2)2}2M(SO)] (M = Fe, Ru, Os): Assessment of density functionals and dispersion interactions

Abstract

Geometry, electronic structure and bonding analysis of the sulfur monoxide complexes [{N(SPMe2)2}2M(SO)] (M=Fe, Ru, Os) have been investigated with the DFT, DFT-D3 and DFT-D3(BJ) methods using density functionals BP86, PW91, BLYP, PBE, revPBE, and TPSS. The BP86 and PBE optimized geometries of complex [{N(SPMe2)2}2Ru(SO)] are in good agreement with the reported experimental values. The Mayer and Gopinathan–Jug bond orders confirm the presence of M–SO and S–O multiple bond characters. Hirshfeld charge analysis shows transfer of electron density from metal fragments to antibonding π∗ orbital of SO ligand. Significant noncovalent interactions between metal fragment and SO ligand are observed in the studied sulfur monoxide complexes. Noncovalent M---O and S---SO interactions have been justified by molecular orbital analysis. The M–SO bond dissociation energies vary in the order Fe<Ru<Os and depends on the choice of density functionals. The BP86/D3(BJ) dispersion corrections add 38% to the bond dissociation energy of Fe–SO bond, while only 22% and 17% to Ru–SO and Os–SO bonds, respectively. The π-bonding contributions to the total M–SO bonds are relatively smaller (22.6–27.0%) than the σ-bonding contribution.