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 [MIV(cp)2(PR2)2](M = Zr, R = Ph; M = Hf, R = Ph or C6H11) or the reduced species [{MIII(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 MIV and MIII 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 MIII→MIV into their reactions.

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