N-Heterocyclic carbene functionalized goup 7-9 transition metal

The N-heterocyclic carbene (NHC) functionalized phosphinidene complexes [(pCy)(IiPr2Me2)- RudPMes*] (4), [(pCy)(IiPr2Me2)OsdPMes*] (6), and [(Cp*)(IiPr2Me2)RhdPMes*] (7) were generated by a double-dehydrohalogenation-ligation sequence of the corresponding primary phosphine complexes with 3 equiv of NHC. The effect of the NHC ligand on the electronic properties of the phosphinidene complexes [(Ring)(NHC)MdPH] (8-16), bearing group 7-9 transition metals and cycloheptatrienyl (Cht+), benzene, and cyclopentadienyl (Cp-) as ancillary ligands, was studied by density functional theory. All ligand-M bond energy strengths increase with the order of the transition metal in the periodic table. The metal-carbene bond (M-NHC) is dominated by σ-interaction from the ligand, but the π-interaction is substantial, contributing up to ∼20% of the total orbital interaction arising from metal to ligand π-back-donation. The charged ligands Cht+and Cp- have notable effects on the total σ- and π-interactions in the M-NHC bond. On going to the right in the periodic table, the structures show an increase inM-NHCbond energy that concurs with the net charge on the phosphorus atom of the MdP bond.