New dihydride- and alkene-η6-arene complexes of iridium

The synthesis of iridium derivatives of general formula [(η6-arene)IrH2(PR3)]BF4 {arene = benzene: R = iPr (1), Cy (2); R = iPr: arene = toluene (4), 1,3,5-trimethylbenzene (5), 1,2,4-trimethylbenzene (6), hexamethylbenzene (7), 1-methylstyrene (8), phenol (9), aniline (10)} and [(η6-arene)Ir(η2-C2H4) (PiPr3)]BF4 {arene = benzene (23), toluene (24), 1,3,5-trimethylbenzene (25), hexamethylbenzene (26)} is described. 1 and 2 have been obtained by treatment of [Ir(μ-OMe)(cod)]2 with [HPR3]BF4, followed by reaction with H2, in acetone/benzene mixtures. A similar synthetic methodology has been used to prepare the naphthalene complex [(η6-C10H8)IrH2 (PiPr3)]BF4 (16) and the thiophene derivative [(η5-SC4H4)IrH2 (PiPr3)]-BF4 (17). Compounds 4-10 have been prepared from 1 by arene substitution in acetone solutions. The substitution reactions involved a tris-acetone intermediate, which has been characterized in acetone-d6, [IrH2(OC(CD3)2)3 (PiPr3)]+ (3). The η6-aniline ligand of 10 can be displaced by three N-bonded anilines, to give the complex [IrH2(Κ-N, NH2Ph)3(PiPr3)]BF4 (11). Other N-containing arenes such as quinoline and isoquinoline gave only products with N-coordinating ligands, 12-15. The treatment of 1 with NaBPh4 led to the zwitterionic compound [Ph3B(η6-Ph)IrH2(Pi Pr3)] (18). This complex has been used as an arene ligand t obtain the compounds [Ph2B{(η6-Ph)IrH2 (PiPr3)}2]BF4 (19), [PhB{(η6-Ph)IrH2 (PiPr3)}3](BF4)2 (20), and [B{(η6-Ph)IrH2 (PiPr3)}4](BF4)3 (21), in which the BPh4 - anion is coordinated to two, three, or four iridium centers, respectively. Treatment of 1 with styrene afforded the Ir(I) compound [(η6-C6H5Et)Ir (η2-CH2=CHPh)(PiPr3)] BF4 (22). Under similar conditions, the reaction of 1, 4, and 5 with ethylene produced ethane and the ethylene complexes 23-25. Compound 26 and the zwitterionic complex [Ph3B(η6-Ph) Ir(η2-C2H4) (PiPr3)] (27) have been prepared by arene displacement from 23. 1 has been found to catalyze, under mild conditions, the hydrogenation of several unsaturated substrates, including imines. The molecular structure of 23 has been determined by X-ray crystallography.We thank the Dirección General de Investigación Científica y Técnica for the support of this research (Project No. PB94-1186). C.O. thanks the Alexander von Humboldt Foundation for a Feodor Lynen Fellowship. G.P. thanks Programa CYTED for a fellowship.Peer Reviewe