Reaction of a Cp*Ir(iii) cation with mono- and di-lacunary Keggin-type heteropolytungstates and a dimer of a hexa-lacunary Dawson-type phosphopolytungstate

Abstract

Reactions of a [Cp*Ir]²⁺ (Cp*: pentamethylcyclopentadienyl) complex, [Cp*IrCl₂]₂, with several lacunary heteropolytungstates are presented. Reactions with mono-lacunary α-Keggin type heteropolytungstates, K₈[α-SiW₁₁O₃₉] and K₇[α-PW₁₁O₃₉], produced Cl⁻-bridged di-Cp*Ir complexes such as [α-SiW₁₁O₃₉(Cp*Ir)₂Cl]⁵⁻ and [α-PW₁₁O₃₉(Cp*Ir)₂Cl]⁴⁻, respectively, where two [Cp*Ir]²⁺ are bridged by Cl⁻ and four oxygens of lacunary sites. A reaction with a di-lacunary γ-Keggin-type silicodecatungstate, K₈[γ-SiW₁₀O₃₆], produced [γ-SiW₁₀O₃₆(Cp*Ir)]⁶⁻, where the [Cp*Ir]²⁺ moiety is attached through three bridging oxygens of the non-lacunary site. A reaction with a dimeric species of a hexa-lacunary Dawson-type phosphotungstate, [P₄W₂₄O₉₄]²⁴⁻, produced a tetra-[Cp*Ir]²⁺ attached cyclic tetramer, [P₈W₄₈O₁₈₄(Cp*Ir(H₂O))₄(WO₂(H₂O)₂)_0.6]^30.8−, where two inner oxygens of the cyclic tetramer and a water oxygen coordinated to Ir. [α-SiW₁₁O₃₉(Cp*Ir)₂Cl]⁵⁻ showed similar catalytic activity for H₂ evolution from formic acid to that of [Cp*IrCl₂]₂.