EFFECTS OF PHOSPHINE ON STRUCTURE AND REDUCTIVE ELIMINATION-REACTIONS OF (C5ME5)RH(PR3)PHH COMPLEXES

The complexes (C5Me5)Rh(PR3)X2, (C5Me5)Rh(PR3)PhX, (C5Me5)Rh(PR3)PhH, and (C5Me5)Rh(PR3)H2 have been prepared for several members of the series where X = Cl or Br and PR3 = PPh3, PMePh2, PMe2Ph, PMe3, PMe2(t-Bu), PMe2(n-Bu), or P(n-Bu)3. The rates at which the phenyl hydride complexes reductively eliminate benzene have been measured. Four members of the series have been structurally characterized, and a comparison is made between the steric and electronic requirements of the phosphine and the rate of benzene elimination, showing the importance of both effects. The complex (C5Me5)Rh(PPh3)PhBr crystallizes in the triclinic space group P1BAR, with a = 15.707 (6) angstrom, b = 19.218 (5) angstrom, c = 10.419 (3) angstrom, alpha = 100.94 (2)-degrees, beta = 98.25 (3)-degrees, gamma = 105.04 (3)-degrees, V = 2920 (4) angstrom 3, and Z = 4. The complex (C5Me5)Rh(PMePh2)PhBr was also structurally characterized, crystallizing in the monoclinic space group P2(1)/n, with a = 13.421 (4) angstrom, b = 11.918 (4) angstrom, c = 17.085 (3) angstrom, beta = 107.54 (2)-degrees, V = 2606 (2) angstrom 3, and Z = 4. The complex (C5Me5)Rh(PMe2Ph)PhBr crystallized in the monoclinic space group P2(1)/n with a = 17.042 (4) angstrom, b = 15.94 (1) angstrom, c = 19.314 (8) angstrom, beta = 115.53 (3)-degrees, V = 4733 (8) angstrom 3, and Z = 8.