Binuclear oxidative addition of hydrogen in diamidonaphthalene-bridged diiridium complexes

The complex [Ir-2(mu-1,8-(NH)(2)naphth)(CO)(2)(Pipr(3))(2)] (1) reacts with triflic acid to give [Ir-2(mu-1,8(NH)(2)naphth)H(CO)(2)(PiPr(3))(2)](CF3SO3) (2), which contains a terminal hydride. Complex 2 reacts with NEt3 to reform 1, but it can also react with a second equivalent of triflic acid to give the asymmetric dihydride complex [Ir-2- (mu-1,8-(NH)(2)naphth)(mu-H)H(OSO2CF3)(CO)(2)(PiPr(3))(2)] (CF3SO3) (3). The triflate ligand of 3 can be replaced by acetone or acetonitrile to give [Ir-2(mu-1,8-(NH)(2)-naphth)(mu-H)H(OC(CH3)(2))(CO)(2)- (PiPr(3))(2)](CF3SO3)(2) (4) and [Ir-2(mu-1,8(NH)(2)naphth) (mu-H)H(NCCH3)(CO)(2)- (PiPr(3))(2)](CF3SO3)(2) (5), respectively. The X-ray structure of 4 revealed the presence of a terminal and an asymmetric bridging hydride. The hydride ligands of 2-4 undergo H/D exchange in D2O or [D-6]acetone. The monohydride 2 reacts with H-2 to give two isomeric compounds of stoichiometry [Ir-2(mu-1,8(NH)(2)naphth) (mu-H)H-2(CO)(2)(PiPr(3))(2)](CF3SO3) (7a, 7b), in which a molecule of hydrogen has been added to form a terminal and a bridging hydride. In the presence of NEt3, 7a and 7b isomerize into the symmetric complex 8 which presents a trans arrangement of the hydrides. Oxidation of complex 1 allows the preparation of the iridium(II) species [Ir-2(mu-1,8-(NH)(2)naphth)(OSO2CF3)(2)-(CO)(2)(PiPr(3))(2)] (9). The triflate ligands of 9 can be replaced by tetrahydrothiophene or acetonitrile to give complexes 10 and 11, respectively. The acetonitrile complexes can exist as three different isomers: two have C-2 symmetry (11a, 11c) and one is asymmetric (11b); the latter has been characterized by X-ray diffraction. The kinetic study of the isomerization reactions reveals these processes to be strictly intramolecular. The reaction of 9 with hydrogen gives different final products, depending on the solvent. Thus, in CDCl3 the dihydride 3 is obtained, whereas in acetone a mixture of the trihydrides 7a and 7b is formed.