Bimetallic systems. Part 16. Formation of Group 6 metal(0)–platinum(II) hydride complexes, by ring opening of fac- or mer-[M(CO)3(dppm-PP′)(dppm-P)](M = Cr, Mo, or W; dppm = Ph2PCH2PPh2). Reactions of [(CO)3Mo(µ-dppm)2PtH(Cl)]

Abstract

The new complexes fac- and mer-[W(CO)₃(dppm-PP′)(dppm-p)](dppm = Ph₂PCH₂PPh₂) are described. Treatment of fac- or mer-[M(CO)₃(dppm-PP′)(dppm-P)](M = Cr, Mo, or W) with trans-[PtH(Cl)(PPh₃)₂] gave the heterobimetallic complexes [(CO)₃M(µ-dppm)₂PtH(Cl)] in good yields. Similarly fac- or mer-[Mo(CO)₃(dppm-PP′)(dppm-P)] reacted with trans-[PtH(CCPh)(PPh₃)₂] to give [(CO)₃Mo(µ-dppm)₂PhH(CCPh)], but the corresponding chromium– or tungsten–platinum complexes could not be prepared. Phosphorus-31 and ¹H n.m.r., and i.r. spectroscopic data are given and discussed. ¹H-{³¹P} N.m.r. studies at different temperatures showed the complexes of type [(CO)₃M(µ-dppm)₂PtH(Y)](M = Cr, Mo, or W, Y = Cl; M = Mo, Y = CCPh) to be fluxional, corresponding to inversion of the M(µ-dppm)₂Pt ring and exchange of positions of the H and Y ligands: a mechanism for this inversion is suggested. The chloride ligand of [(CO)₃Mo(µ-dppm)₂PtH(Cl)] was found to be readily substituted by nucleophiles Y (Y = Br, CN, N₃, H, or CO) to give new heterobimetallic species. Treatment of [(CO)₃Mo(µ-dppm)₂PtH(Cl)] with NaBH₄ gave a heterobimetallic dihydride with a bridging and a terminal hydride. ¹H-{³¹P} N.m.r. studies showed this dihydride to undergo bridging-to-terminal hydride exchange at +21 °C in solution.