Reactions of rhodium trifluoroacetate with triphenylphosphine and pyridine. Molecular structure of Rh 2(O 2CCF 3) 4(py) 4

Abstract

Rh 2(O 2CCF 3) 4 reacts with two mol of triphenylphosphine forming the adduct Rh 2(O 2CCF 3) 4(PPh 3) 2. This compound in solution, even at room temperature, undergoes slow stepwise orthometalation of the phosphine ligands forming the doubly metalated compound Rh 2(O 2CCF 3) 2[(C 6H 4)P(C 6H 5) 2] 2. This reaction has been monitored by 31P NMR spectroscopy detecting in solution three reaction intermediates. Rh 2(O 2CCF 3) 4 reacts with excess of pyridine to form the compound Rh 2(O 2CCF 3) 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) Å, β=96.416(8)°, V=6686.6(8) Å 3, Z=8, D x=1.94 Mg/m 3. Mo Kα radiation (graphite crystal monochromator, λ=0.71073 Å), μ(Mo Kα)=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.