Transition metal–phosphide chemistry: synthesis of [M(η-C5H5)2(PR2)2](M = Zr, R = Ph; M = Hf, R = Ph or cyclo-C6H11) and [{M(η-C5H5)2(PR2)}2](M = Ti, R = Ph or Me; M = Zr or Hf, R = Me), and their reactions with protic and halogen-containing species

Abstract

Reactions of the metallocene dichlorides [M(cp)₂Cl₂](M = Ti, Zr, or Hf; cp =η-C₅H₅) with stoicheiometric amounts of LiPR₂(R = Me, Ph, or cyclo-C₆H₁₁) yield either the direct exchange products [M^IV(cp)₂(PR₂)₂](M = Zr, R = Ph; M = Hf, R = Ph or C₆H₁₁) or the reduced species [{M^III(cp)₂(PR₂)}₂](M = Ti, R = Me or Ph; M = Zr or Hf, R = Me). Spectral (i.r. and ¹H n.m.r.) characterisation of these compounds is presented and discussed with suggestions of possible structures. Treatment of [Zr(cp)₂(PPh₂)₂] with PPh₂Cl affords the ‘mixed’ chloro–phosphddo-compound [Zr(cp)₂Cl(PPh₂)]. Reactions of both the M^IV and M^III species with halogen-containing and protic reagents have been investigated. Each series reacts with smooth cleavage of the M–P bond(s), but whereas the compounds [M(cp)₂(PR₂)₂](M = Ti, Zr, or Hf) show simple metathetical exchange, [{M(cp)₂(PR₂)}₂] usually (and in the case of M = Zr or Hf exclusively) also incorporate metal oxidation M^III→M^IV into their reactions.