Molybdenum and tungsten complexes of the neutral tripod ligands HC(pz)3 and MeC(CH2PPh2)3

Starting from [M(CO)6], seven-coordinated complexes of tungsten and molybdenum containing the facially coordinating ligands HC(pz)3 (1) and MeC(CH2PPh2)3 (2) were obtained in a two-step reaction sequence. The complexes have a 4:3 piano stool geometry with almost perfect CS symmetry in the crystal. In solution, they show the typical fluxional behavior for seven-coordinated complexes even at low temperature. Complete oxidative decarbonylation occurs when [HC(pz)3Mo(CO)3] (4) or [MeC(CH2PPh2)3Mo(CO)3] (6) are treated with an excess of I2 or Br2.