Reactivity of Organoiridium Tungsten Oxide Clusters with Transition Metal Aquo Cations.

Organometallic-polyoxometalate (POM) complexes form a unique class of molecular organometallic oxides characterized by the dynamic behavior of the organometallic cations. Herein, we investigated the reactivity of Cp*Ir-octatungstate clusters (where Cp* represents pentamethylcyclopentadienyl, C5 Me5 - ) with Werner-type transition-metal aquo cations. The addition of Ag+ , Co2+ , Ni2+ , and M3+ (M = Cr, Fe, or In) cations to the aqueous solution of Cp*Ir-octatungstate clusters resulted in the formation of [{Ag(OH2 )2 }2 {Cp*Ir(OH2 )}2 {Cp*IrW3 O12 (OH)}2 (WO2 )2 ] ( 1 ), Co1.5 K0.8 Na0.2 [{ trans -Co(OH2 )2 }{Cp*IrW3 O12 (OH)}2 (WO2 )1.3 { cis -Co(OH2 )2 }0.7 ] ( 2-Co ), Ni0.2 K1.4 Na0.2 [{Ni(OH2 )4 }2 {Cp*IrW3 O12 (OH)}2 (WO2 )1.1 { cis -Ni(OH2 )2 }0.9 ] ( 2-Ni ), and [{M(OH2 )4 }2 {Cp*IrW3 O12 (OH)}2 { cis -M(OH2 )2 }2 ](NO3 )2 (M = Cr, 3-Cr ; Fe, 3-Fe ; or In, 3-In ), respectively. All clusters share the same cubane-type {Cp*IrW3 O12 (OH)}5- building block, representing the first examples of organoiridium-POMs functionalized by transition-metal aquo cations. These compounds are insoluble in water, facilitating the evaluation of their heterogeneous water-oxidation properties. Notably, 2-Co generates the highest catalytic water oxidation current. This work provides a new synthetic method to introduce metal-aquo complexes on an organometallic oxide cluster, producing multimetallic molecules that model the catalytic sites of complex oxides.