Chiral polytungstometalates [WM₃(H₂O)₂(XW₉O₃₄)₂]^12–(X = M = Zn or Co^II) and their M-substituted derivatives. Syntheses, chemical, structural and spectroscopic study of some<scp>D</scp>,<scp>L</scp>sodium and potassium salts

Abstract

Heteropolyanions [WM3(H2O)2(XW9O34)2]12–(X = M = Zn or CoII) form on ageing concentrated solutions of sodium salts of the well known polyanions [Zn(H2O)(ZnW11O39)]8– and [CoII(H2O)(CoIIW11O39)]8–. Their high-yield syntheses are reported. An X-ray crystallographic study of Na12[WZn3(H2O)2(ZnW9O34)2]·46H2O [Space group p21/c, a= 13.027(4), b= 17.788(5), c= 24.124(4)Å, β= 118.94(2)°, Z= 2, R′= 0.051 for 3783 reflections] and its high-resolution 183W NMR spectrum (ten lines, one with half the intensity of the others) reveal that the polyanion is isotypical of the earlier described [M4(H2O)2(PW9O34)2]10– anions (M = Zn or CoII) and elucidate the puzzling analytical composition Zn5W19. However, the lower point-group symmetry C2 (instead of C2h) points to the existence of enantiomers. This anion and the homologous cobalt(II) anion are always obtained as racemic mixtures. Both parent anions transform into substitution derivatives by replacement of atoms in M positions (Two or three for Zn, two only for Co) by transition elements: derivatives of MnII or MnIII, FeII or FeIII, CoII, NiII, CuII, Zn, PdII, PtII and VIV are reported. The structures of D,L-Na12[WCu3(H2O)2(ZnW9O34)2]·48H2O and D,L-K12[WZnV2O2(ZnW9O34)2]·30H2O are also described and compared. Chemical features, comparative electronic UV–VIS spectra, and 183W NMR spectra of these series are discussed.