Molybdenum and tungsten complexes with carbon dioxide and ethylene ligands

The first examples of stable metal complexes with coordinated ethylene and carbon dioxide ligands are reported. Reaction of tris(ethylene) complexes mer-M(C₂H₄)₃(PNP) (M = Mo and W; PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) with CO₂ yields the corresponding, mixed cis-M(C₂H₄)₂(CO₂)(PNP) derivatives. X-ray studies reveal six-coordinate structures exhibiting η²-ethylene and κ²-C,O carbon dioxide coordination. Remarkably, the formation of the molybdenum CO₂ adduct occurs also in the solid state at room temperature, under 4 bar of CO₂, in a nearly quantitative manner.