SYNTHESIS, STRUCTURE AND HYDROGENATION OF ETA-3-BENZYL DIPHOSPHINE COMPLEXES OF RHODIUM AND IRIDIUM

The preparation of(COD)Rh(eta3-CH2Ph) is described starting from [(COD)Rh]2(mu-Cl)2 by the addition of either Zn(CH2Ph), or Mg(CH2Ph)2(THF)2. The addition of the bulky chelating diphosphines tBu2P(CH2)3PtBu2, iPr2P(CH2)3PiPr2, iPr2P(CH2)2PiPr2, iPr2PCH2PiPr2 and Cy2PCH2PCy2 to (COD)Rh(eta3-CH2Ph) yields the coordinatively unsaturated, four-coordinate rhodium complexes of the form P2Rh(eta3-CH2Ph). Iridium complexes of the form P2Ir(eta3-CH2Ph)(where P2 = tBu2P(CH2)3PtBu, and iPr2P(CH2)3PiPr2) can be prepared from [P2Ir]2(mu-Cl), and Zn(CH2Ph)2 or Mg(CHPh)2(THF)2. Reaction of the benzyl complexes with H-2 (1 atM) yields binuclear hydride derivatives of varying composition depending on the chelate ring size of the coordinated diphosphine. For the diphosphines with only a single methylene in the backbone, binuclear hexahydride complexes are formed in which the diphosphine is binucleating. The X-ray structure of {iPr2P(CH22)3PiPr2}Rh(eta3-CH2Ph) shows a square planar geometry about rhodium with alternating single and double bonds in the eta3-coordinated benzyl fragment. Crystals of (1,3-bis(diiso-propylphosphino)propane}rhodium(eta3-benzyl) are monoclinic, a = 10.540(3), b = 15.030(9), c = 14.858(5) angstrom, beta = 92.91(3)-degrees, Z = 4, D(c) = 1.329 g cm-3, space. group P2(1)/n. The structure was solved bv the Patterson method and was refined by full-matrix least-squares procedures to R = 0.036 and R(w) = 0.043 for 4152 reflections with I > 3sigma(I).