REACTIONS OF RHODIUM TRIFLUOROACETATE WITH TRIPHENYLPHOSPHINE AND PYRIDINE - MOLECULAR-STRUCTURE OF RH2(O2CCF3)4(PY)4

Rh2(O2CCF3)4 reacts with two mol of triphenylphosphine forming the adduct Rh2(O2CCF3)4(PPh3)2. This compound in solution, even at room temperature, undergoes slow stepwise orthometalation of the phosphine ligands forming the doubly metalated compound Rh2(O2CCF3)2[(C6H4)P(C6H5)2]2. This reaction has been monitored by P-31 NMR spectroscopy detecting in solution three reaction intermediates. Rh2(O2CCF3)4 reacts with excess of pyridine to form the compound Rh2(O2CCF3)4(py)4 that can be structurally classified as a class III adduct. It contains two bridging and two monodentate equatorial carboxylates and two equatorial and two axial pyridine ligands. The structure of this compound has been determined by X-ray diffraction. M(r) = 974.3, monoclinic, space group P2(1)/n, a = 10.504(1), b = 18.108(1), c = 35.377(1) angstrom, beta = 96.416(8)degrees, V = 6686.6(8) angstsrom3, Z = 8, D(x) = 1.94 Mg/m3. Mo Kalpha radiation (graphite crystal monochromator, lambda = 0.71073 angstrom), mu(Mo Kalpha) = 10.89 cm-1, F(000) = 3824, T = 293 K. Final conventional R factor = 0.12 for 2258 'observed' reflections and 312 variables. The structure was solved by Patterson interpretation using the program SHELXS86 and the Fourier synthesis.