A New Method for the Synthesis of Organopolyoxometalate Hybrid Compounds

The reaction of a quaternary ammonium salt of the tin chloride-substituted polyoxometalate, [PSn(Cl)W₁₁O₃₉]^4-, with a variety of n-nucleophiles including primary, secondary, and tertiary amines and a tertiary phosphine, yielded tin-centered Lewis acid−base adducts, [PSn(Cl)W₁₁O₃₉]^4-−n-nucleophile; with more nucleophilic secondary amines such as diisopropylamine, apparently some [PSnN[CH(CH₃)₂]₂W₁₁O₃₉]^4- was formed as a minor product. The compounds were identified by ¹H, ¹¹⁹Sn, ¹⁵N, ³¹P, and ¹⁸³W NMR, ESI-MS, and elemental analyses. The key connectivity of the Sn−Cl center with the amine was clarified by the observation of ³J Sn−H couplings (Sn from the polyoxometalate cluster and H from the amine moiety) in a 2D ¹¹⁹Sn−¹H heteronuclear multiple-bond correlation NMR experiment. This new, rather simple synthetic method was also utilized for preparing amino acid−polyoxometalate hybrid compounds.