C-H ACTIVATION OF ETHENE BY NON-CYCLOPENTADIENYL-CONTAINING IRIDIUM COMPLEXES - SUPPORTING ROLE OF IPR2PCH2CH2OME AS PHOSPHINE LIGAND

UV irradiation of trans-[IrCl(C2H4)(PiPr3)2] (4) in toluene gives only small amounts of the hydrido(vinyl)iridium isomer [IrH(CH=CH2)Cl(PiPr3)2] (5). If, however, the photolysis is carried out in the of pyridine, a mixture of two isomers of [IrH(CH=CH2)Cl(py)(PiPr3)2] (6a,b) is formed in 88% yield. Displacement of pyridine by CO gives [IrH(CH=CH2)Cl(CO)(PiPr3)2] (7). Photolysis of trans-[IrCl-(C2H4)(eta-1-iPr2PCH2CH2OMe)2] (8) in toluene proceeds rapidly and leads to the quantitative formation of [IrH(CH=CH2)Cl(eta-1-iPr2PCH2CH2OMe)(eta-2-iPr2PCH2CH2OMe)] (9). Compound 9, which in solution shows a fluxional behavior (DELTA-G(double dagger) ca. 41 kJ/mol in toluene), also reacts with CO to give [IrH(CH=CH2)-Cl(CO)(eta-1-iPr2PCH2H2OMe)2] (10). The thermal reaction of 9 regenerates the pi-ethylene complex 8, whereas the carbonyl(hydrido)vinyl derivative 10 reacts in refluxing benzene to form ethylene and the four-coordinate carbonyliridium compound trans- [IrCl(CO)(eta-1-iPr2PCH2CH2OMe)2] (11). The X-ray crystal structure of 7 has been determined (triclinic space group P1BAR (No. 2) with a = 8.848 (3) angstrom, b = 9.876 (4) angstrom, C = 16.200 (6) angstrom, alpha = 72.38 (2)-degrees, beta = 75.10 (2)-degrees, gamma = 78.62 (2)-degrees, and Z = 2).