The synthesis of six- and seven-coordinate molybdenum and tungsten(II) dicarbonyl complexes containing monodentate phosphine ligands

Abstract

On passing a stream of dry N 2 gas through a solution of Mo(CO) 3(PR 3) 2X 2 (PR 3 = PEtPh 2, PMe 2Ph or PEt 2Ph, X = Br; PR 3 = PMePh 2, X = Cl, Br or I) in acetonitrile at room temperature, or W(CO) 3- (PR 3) 2X 2 (PR 3 = PMePh 2 or PMe 2Ph, X = Br) in boiling acetonitrile, the yellow, monomeric 7- coordinate dicarbonyls M(CO) 2(NCMe)(PR 3) 2X 2 are formed in high yields. The nitrile ligand is readily displaced from M(CO) 2(NCMe)(PR 3) 2X 2 (M = Mo, PR 3 = PEtPh 2 or PEt 2Ph, X = Br; PR 3 = PMePh 2, X = I; M = W, PR 3 = PMePh 2, X = Br) by passing a vigorous stream of N 2 gas through a solution of these complexes dissolved in chlorinated or ketonic solvents yielding new, highly coloured 6-coordinate d 4 M(CO) 2(PR 3) 2X 2 derivatives.