Carbene precursors and metal complexes : The synthesis and structure of dichloro(difluoromehtyl)- carbonylbis(triphenylphosphine)iridium(III), IrCl 2(CHF 2)(CO)- (PPh 3) 2

Abstract

The complex IrCl 2(CHF 2)(CO)(PPh 3) 2 is synthesized by the thermal decomposition of IrCl(CHF 2)(OCOCF 2Cl)(CO)(PPh 3) 2 or by the extended reaction of Vaska's complex, IrCl(CO)(PPh 3) 2, with the carbene precursor CF 2ClCOONa. The crystal and molecular structure of IrCl 2(CHF 2)(CO)(PPh 3) 2 has been determined from three dimensional X-ray data by standard heavy atom methods. The complex crystallizes in space group P2 2/ c of the monoclinic system in a cell of dimensions a 10.47(1), b 14.45(2), c 24.58(2) Å, β 97.68(5) o and V 3865 Å 3. The molecular structure of the complex consists of a slightly distorted octahedron with trans phosphine ligands. The difluoromethyl group is trans to a chlorine atom with an IrC(1) distance of 2.19(3) Å. the existence of the proton of the difluoromethyl group is suggested by the bond angles about C(1), and is confirmed by a deuterium labelling experiment. The thermal composition of IrCl(CHF 2)(OCOCF 2Cl)(CO)(PPh 3) 2 to give IrCl 2(CHF 2)(CO)(PPh 3) 2 in quantitative yield is discussed as a means of generating CF 2. Extension to other O- coordinated α-halocarboxylates is proposed.