Synthesis and structural characterization of new organotin derivatives of polyoxotungstates via transmetallation and coupling reactions

Organotin-substituted polyoxometalates [WM(RSn)2(MW9O34)2]10−; (M = Co, Zn; R = CH3, C2H5, n-C4H9) have been prepared through exchange reaction of [WM3(H2O)2(MW9O34)2]12− and the appropriate organotin trichloride in aqueous solution. The complexes have been characterized in solution by 183W and 119Sn NMR spectroscopy of the diamagnetic anions, and by single crystal structure determinations of salts of the methyl, ethyl and n-butyl derivatives of the tungstozincates and of the methyl derivative of a CoZn2 analog. Cyclic voltammetry demonstrates for the first time for this class of polyoxometalates that the tetrahedral cobalt(II) centers are reversibly oxidizable to yield high-spin cobalt(III) analogs. Displacement of the kinetically metastable [W5O18]6− anion from [Ce(W5O18)2]10−, by reaction with CH3SnCl3, leads to modest yields of [CH3SnW5O18]3−. Bis(trichlorostannyl)alkanes such as Cl3Sn(CH2)4SnCl3 can be used as covalent linkers of polyoxometalate anions to form the “dumbbell” complex [SiW11O39Sn(CH2)4SnSiW11O39]10− and linear oligomers {[(Sn(CH2)4Sn)(WZn(ZnW9O34)2)]10−}x.

Insertion of {RSn}3+ into polyoxoytungstate structures by displacement of transition metal centers has been demonstrated with the chiral Tourné–Zonnevijlle anions and with [Ce(W5O18)2]9−. Robust coupling of polyoxotungstates is achieved by the use of {Sn(CH2)nSn}6+ as linkers.Figure optionsDownload as PowerPoint slide