Molar-Ratio-Dependent Coordination Assembly of Organoiridium(III)-Octatungstate Complexes in Aqueous Solution.

We scrutinized the speciation of Cp*Ir-containing tungsten oxide clusters (Cp* is pentamethylcyclopentadienyl anion) in aqueous mixtures of [(Cp*IrCl)(μ-Cl)] and NaWO in varying molar ratios. H nuclear magnetic resonance (NMR) spectroscopy revealed the formation of three distinct Cp*Ir-polyoxotungstate species in the reaction solution, and they were isolated as Na[(Cp*Ir)(μ-OH)][(Cp*Ir)HWO] (), [(Cp*Ir)(μ-OH)][(Cp*Ir){Cp*Ir(OH)}HWO] (), and [(Cp*Ir){Cp*Ir(OH)}{Cp*Ir(OH)}HWO](NO) () from the mixtures in which iridium concentration is less than, equal to, and more than the tungsten concentration, respectively. These results show the octatungstate [HWO] anion is the major polyoxotungstate species in the presence of {Cp*Ir} cations, and it has high nucleophilicity enough to bind up to six {Cp*Ir} cations on its surfaces producing a Cp*Ir-octatungstate complex. The octatungstate anion was also generated from the reaction of [(Cp*IrCl)(μ-Cl)] and methylammonium paratungstate-B, (CHNH)[HWO], and was isolated as a methylamine-coordinated complex (CHNH)[(Cp*Ir){Cp*Ir(NHCH)}HWO] (), indicating {Cp*Ir} cations function as a structure-directing agent that converts tungsten species into octatungstate anions in aqueous solution. In addition, the coordination environment of {Cp*Ir} can be further modified by coordination with pyridine forming [{Cp*Ir(NCH)}(μ-OH)][(Cp*Ir){Cp*Ir(NCH)}HWO] ().