Synthesis and characterization of chromium and molybdenum(0) complexes bearing the (pentafluoroethyl)diphenylphosphine (pfepp) ligand

The synthesis and characterization of two Group VI pentacarbonyl complexes (pfepp)M(CO)5 (M = Cr 1, Mo 2; pfepp = PPh2C2F5) are reported. Thermolysis of M(CO)6 and pfepp in refluxing octane afforded 1 and 2 in moderate yields. These complexes were completely characterized by multinuclear NMR, IR and elemental analysis. X-ray structures for these complexes indicated they were isostructural, crystalizing in triclinic unit cells with four molecules per asymmetric unit. A comparison of the bond lengths in 1 and 2 to other (L)M(CO)5 complexes showed a relationship between the M–Cax bond length and the electronic influence of the phosphine ligand, and establishes the pfepp ligand as neither electron-rich nor electron-poor. A comparison of IR data with other (L)M(CO)5 complexes also indicates the pfepp ligand is electronically neutral, with an electronic influence that approximates phosphites.