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-d 6, [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(PiPr3)] (18). This complex has been used as an arene ligand to 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.

The preparation is described of two modified derivatives of the tripodal tetraamine tren, 2-hydroxy-N,N-bis(2-aminoethyl)ethylamine, NN(2)O222, and 2-amino-N,N-bis(2-hydroxyethyl)ethylamine, NNO(2)222, in which one and two primary amines, respectively, have been replaced with hydroxyl groups. The aqueous acid-base and metal ion (Ni2+, Cu2+, Zn2+) coordination properties of these two compounds were studied by potentiometric, spectrophotometric, and NMR titrations. Two and three acidity constants, respectively, were determined for NNO(2)222 and NN(2)O222 by potentiometry. NMR titrations proved that deprotonation of the two OH residues in NNO(2)222, and of the one in NN(2)O222, corresponded to pK(a) > 14. Acidity constants related to deprotonation of the terminal primary amine functions were similar in both NNO(2)222 and NN(2)O222 (and to those in the parent compound tren), whereas deprotonation of the tertiary ammonium N atom had a very different acidity constant in each of these three compounds. Charge repulsion, polar effects, and intramolecular hydrogen bond formation are responsible for the discrepancy. Chelated diamine metal complexes for each ligand studied depended only on the basicity of the corresponding two amines, suggesting that the hydroxyl group interacted with the metal ion very weakly in acidic or neutral solutions. The ML2+ species further deprotonated to form M(L - H)+ and M(L - 2H) complexes, in which the protons are released from the coordinated OH group. A pM vs pH correlation showed that replacing an NH2 group with a OH group in tren or NN(2)O222 makes the resulting metal complex less stable. Electronic spectra showed that the Cu(II) complexes of both NNO(2)222 and NN(2)O222 adopted a square pyramidal geometry rather than a trigonal bipyramidal geometry. The X-ray crystal structure analysis of the zinc complex [Zn(OH)(mu-NNO(2)222 - H)Zn(NNO(2)222)]2+, as its [BF4]- salt, shows a dinuclear molecule containing two zinc ions, each coordinated in a distorted trigonal bipyramid. The coordination environment at one zinc atom is composed of the four donor groups of a mono-O-deprotonated ligand NNO(2)222 and a hydroxyl ion with the central nitrogen atom of the ligand and the hydroxyl ion in equatorial positions. The oxygen atom of the deprotonated alkoxo group bridges to the second zinc atom, which is coordinated by this atom and one undeprotonated ligand NNO(2)222.