Synthesis, Characterization, and Electrochemical Analyses of Vanadocene Tetrametaphosphate and Phosphinate Derivatives

Abstract

The synthesis and characterization of a series of new vanadocene-derived tetrametaphosphate or diphenylphosphinate complexes, [PPN]2[CpV(P4O12)] (1), [Cp2VOP(O)Ph2] (2), [CpV(μ2-O2PPh2)4VCp] (3), and [Cp2V(μ2-O2PPh2)2VCp2][PF6]2 (4), is reported ([PPN]+ = bis(triphenylphosphoranylidene)ammonium; Cp = η5-cyclopentadienyl). The complexes were synthesized from the methyl vanadocene (Cp2VMe) precursor, through protonation of the Me or Cp linkages using the tetrametaphosphate or phosphinate acid precursors [PPN]2[P4O12H2] (for 1) and Ph2P(O)OH (for 2 and 3). Oxidation of 2 with [Fc][PF6] resulted in dimerization, yielding the bimetallic 4 ([Fc]+ = ferrocenium). Electrochemical analysis of this reaction revealed a possible ECE mechanism that includes prior and subsequent electron transfer to this dimerization. The electronic structure of the dimer 4 was probed by SQUID magnetommetry and X-band EPR spectroscopy (100 and 4 K). The dimer was found to contain two antiferromagnetically coupled VIV centers, as well a...