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

The synthesis of iridium derivatives of general formula [(eta (6)-arene)IrH2(PR3)]BF4 (arene = benzene: R = Pr-i (1), Cy (2); R = Pr-i: arene toluene (4), 1,3,5-trimethylbenzene (5), 1,2,4-trimethylbenzene (6), hexamethylbenzene (7), 1-methylstyrene (8), phenol (9), aniline (10)} and [(eta (6)-arene)Ir(eta (2)-C2H4)((PPr3)-Pr-i)]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(mu -OMe)(cod)](2) with [HPR3]BF4, followed by reaction with H-2, in acetone/benzene mixtures. A similar synthetic methodology has been used to prepare the naphthalene complex [(eta (6)-C10H8)IrH2((PPr3)-Pr-i)]BF4 (16) and the thiophene derivative [(eta (5)-SC4H4)IrH2((PPr3)-Pr-i)]- 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-d(6), [IrH2(OC(CD3)(2))(3)((PPr3)-Pr-i)](+) (3). The eta (6)-aniline ligand of 10 can be displaced by three N-bonded anilines, to give the complex [IrH2(kappa -N, NH2Ph3)((PPr3)-Pr-i)]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 2 zwitterionic compound [Ph3B(eta (6)-Ph)IrH2((PPr3)-Pr-i)] (18). This complex has been used as an arena ligand to obtain the compounds [Ph2B((eta (6)-Ph)IrH2((PPr3)-Pr-i)}(2)]BF4 (19), [PhB((eta (6)-Ph)IrH2((PPr3)-Pr-i)}(3)](BF4)(2) (20), and [B{(eta (6)-Ph)IrH2((PPr3)-Pr-i)}(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 [(eta (6)-C6H5Et)Ir(eta (2)-CH2=CHPh)((PPr3)-Pr-i)]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(eta (6)-Ph)Ir(eta (2)-C2H4)(PiPr(6))] (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.