4-LEGGED PIANO STOOL MOLYBDENUM(II) COMPOUNDS WITHOUT CARBONYL LIGANDS .4. CYCLOPENTADIENYLMOLYBDENUM(II) COMPLEXES WITH 16-ELECTRON AND 18-ELECTRON CONFIGURATIONS

Monocydopentadienyl complexes of Mo(II) with 16- and 18-electron confi gurations of the form (Ring)MoClL(x) (x = 2, Ring = Cp, L = PMe(2)Ph; x = 2, Ring = Cp, L = PMe(3), PMe(2)Ph, L(2) = dppe; x = 3, Ring = Cp , L = PMe(2)Ph) are described. All of the 16-electron complexes are pa ramagnetic with an S = 1 ground state, as shown by magnetic measuremen ts in the solid state and in solution, and by the contact-shifted H-1 NMR spectra. The structure of CpMoCl(dppe) was determined by X-ray di ffraction methods. The 18-electron complex CpMoCl(PMe(2)Ph)(3) has bee n synthesized by reduction of {CpMoCl(2)}(n) with Na in the presence o f 3 equiv of phosphine. It has been fully characterized by H-1 and P-3 1 NMR, chemical analysis, and X-ray structural determination. Thermoly sis of a THF or C6D6 solution of this 18-electron species generates th e 16-electron paramagnetic Mo(II) complex CpMoCl-(PMe(2)Ph)(2). The Cp MoClL(2) (L = PMe(3) and PMe(2)Ph) systems react with 2-electron-dono r ligands, i.e. CO and H-2, to afford stable 18-electron complexes. Th e carbonyl derivative CpMoCl(CO)(PMe(2)Ph)(2) has also been character ized by X-ray crystallography.