Cyclopentadienylvanadium(III) and -vanadium(II) Methyl, Phenyl, and Borohydride Compounds

Reaction of CpVCl2(PMe3)2 with MeLi and PhMgBr yields CpVMe2(PMe3)2 and CpVPh2(PMe3)2, respectively. Conproportionation of CpVCl2(PMe3)2 and CpVMe2(PMe3)2 gives selective conversion to CpVMe(Cl)(PMe3)2. These paramagnetic compounds show isotropic 1H NMR shifts of the P-Me protons. CpVMe2(PMe3)2 reacts rapidly with CO to give acetone and diag-CpV(CO)2(PMe3)2. Borohydride converts CpVCl(Me2PCH2CH2PMe2) to CpV(η2-BH4)(dmpe), shown to have one unpaired electron, two less than its chloride precursor. Conversion of this monochloride to CpVR(dmpe) occurs with MeLi and PhMgBr. The monomethyl compound has a low VC-H stretching frequency (2750 cm-1), but the crystal structure shows no agostic hydrogen to be involved. Crystal data (-158 °C): a = 12.526 (3) Å, b = 9.285 (2) Å, c = 12.772 (3) Å, Z = 4 in space group P212121