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

Abstract

Organotin-substituted polyoxometalates [WM(RSn) 2(MW 9O 34) 2] 10−; (M = Co, Zn; R = CH 3, C 2H 5, n-C 4H 9) have been prepared through exchange reaction of [WM 3(H 2O) 2(MW 9O 34) 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 CoZn 2 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 [W 5O 18] 6− anion from [Ce(W 5O 18) 2] 10−, by reaction with CH 3SnCl 3, leads to modest yields of [CH 3SnW 5O 18] 3−. Bis(trichlorostannyl)alkanes such as Cl 3Sn(CH 2) 4SnCl 3 can be used as covalent linkers of polyoxometalate anions to form the “dumbbell” complex [SiW 11O 39Sn(CH 2) 4SnSiW 11O 39] 10− and linear oligomers {[(Sn(CH 2) 4Sn)(WZn(ZnW 9O 34) 2)] 10−} x .