Synthesis, reactivity, spectroscopic characterization, X-ray structures, PGSE, and NOE NMR studies of (eta(5)-C(5)Me(5))-rhodium and -iridium derivatives containing bis(pyrazolyl)alkane ligands

Rhodium(III) and iridium(III) complexes containing bis(pyrazolyl)methane ligands (pz = pyrazole, L' in general; specifically, L(1) = H(2)C(pz)(2), L(2) = H(2)C(pz(Me2))(2), L(3) = H(2)C(pz(4Me))(2), L(4) = Me(2)C(pz)(2)), have been prepared in a study exploring the reactivity of these ligands toward [Cp*MCl(mu-Cl)](2) dimers (M = Rh, Ir; Cp* = pentamethylcyclopentadienyl). When the reaction was carried out in acetone solution, complexes of the type [Cp*M(L')Cl]Cl were obtained. However, when L(1) and L(2) ligands have been employed with excess [Cp*MCl(mu-Cl)](2), the formation of [Cp*M(L')Cl][Cp*MCl(3)] species has been observed. PGSE NMR measurements have been carried out for these complexes, in which the counterion is a cyclopentadienyl metal complex, in CD(2)Cl(2) as a function of the concentration. The hydrodynamic radius (r(H)) and, consequently, the hydrodynamic volume (V(H)) of all the species have been determined from the measured translational self-diffusion coefficients (D(t)), indicating the predominance of ion pairs in solution. NOE measurements and X-ray single-crystal studies suggest that the [Cp*MCl(3)](-) approaches the cation, orienting the three Cl-legs of the "piano-stool" toward the CH(2) moieties of the bis(pyrazolyl)methane ligands. The reaction of 1 equiv of [Cp*M(L')Cl]Cl or [Cp*M(L')Cl][Cp*MCl(3)] with 1 equiv of AgX (X = ClO(4) or CF(3)SO(3)) in CH(2)Cl(2) allows the generation of [Cp*M(L')Cl]X, whereas the reaction of 1 equiv of [Cp*M(L')Cl] with 2 equiv of AgX yields the dicationic complexes [Cp*M(L')(H(2)O)][X](2), where single water molecules are directly bonded to the metal atoms. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. The reaction of [Cp*Ir(L')(H(2)O)][X](2) with ammonium formate in water or acetone solution allows the generation of the hydride species [Cp*Ir(L')H][X].