NOVEL DINUCLEAR AND TRINUCLEAR OXOPEROXOSULFATO SPECIES IN MOLYBDENUM(VI) AND TUNGSTEN(VI) CHEMISTRY - THE KEY ROLE OF PAIRS OF BRIDGING PEROXO GROUPS

Novel oxoperoxosulfatometalate species are formed in the MO(3) . xH(2) O and MO(4)(2-)/H2O2-H2O/H2SO4/Q(+)HSO(4)(-) systems, where M = Mo or W. They can be isolated as onium salts: C4H9)(4)N](2)[(SO4){M(2)O(2)(m u-O-2)(2)(O-2)(2)}], (3: M = Mo and 4: M = W), [(CH3)(4)N](3)[(HSO4)(S O4){W3O6(O-2)(3)}]. 3.5H(2)O, 5. The structure of 3 (orthorhombic Pcnb , a = 14.850(2), b = 15.949(2), c = 18.892(2) Angstrom), Z = 4, was re fined to R = 0.067 and R(w) = 0.068. The polyanion has one bridging an d one side-on peroxo group on each Mo centre; the [SO4](2-) anion also has a bridging role. 4 is isomorphous (orthorhombic Pcnb, a = 14.834( 4), b = 16.005(3), c = 18.833(3)). The structural features compare wel l with those of previously described complexes n-C4H9)(4)N](2)[(RXO(3) ){W2O2(mu-O-2)(2)(O-2)(2)}] (where R = OH, X(n+) = P(V), As(V) and R = CH3, X(n+) = As(V)). The structure of 5 (monoclinic P2(1)/n, a = 13.6 04(4), b = 15.690(7), c = 32.768(9) Angstrom, beta = 101.82(2)degrees, Z = 8) was refined to R = 0.068 and R(w) = 0.077. This trinuclear spe cies has a side-on peroxo group on each tungsten centre; bridging liga nds are ore, sulfate and hydrogenosulfato groups. The anions are held together in the lattice by H2O molecules, which are hydrogen-bonded be tween two O atoms and the [HSO4](-)-hydrogen atom. The vibrational dat a suggest that these peroxo complexes retain their structures in aceto nitrile or dichloromethane. The dinuclear anionic complexes containing the M(2)O(2)(mu-O-2)(2)(O-2)(2) moiety are among the most efficient f or the transfer of active oxygen to olefinic substrates at room temper ature.