The invention relates to polyoxometalates represented by the formula (A.sub.n).sup.m+{M′.sub.s[M″M.sub.12X.sub.8O.sub.yR.sub.zH.sub.q]}.sup.m− or solvates thereof, corresponding supported polyoxometalates, and processes for their preparation, as well as corresponding metal-clusters, optionally in the form of a dispersion in a liquid carrier medium or immobilized on a solid support, and processes for their preparation, as well as their use in reductive conversion of organic substrate.

The invention relates to polyoxometalates represented by the formula (A.sub.n).sup.m+{M′.sub.s[M″M.sub.12X.sub.8O.sub.yR.sub.zH.sub.q]}.sup.m− or solvates thereof, corresponding supported polyoxometalates, and processes for their preparation, as well as corresponding metal-clusters, optionally in the form of a dispersion in a liquid carrier medium or immobilized on a solid support, and processes for their preparation, as well as their use in reductive conversion of organic substrate.

Provided is a catalyst for producing an unsaturated carboxylic acid, in which a ratio of a diffraction line intensity of 2=19.10.3 with respect to a diffraction line intensity of 2=10.70.3 in X-ray diffraction measurement is 0.20 or more and less than 0.58, and the catalyst having an active component represented by formula (A) shown below:

Mo.sub.10V.sub.aP.sub.bCu.sub.cAs.sub.dX.sub.eO.sub.g(A)

Provided is a catalyst for producing an unsaturated carboxylic acid, in which a ratio of a diffraction line intensity of 2=19.10.3 with respect to a diffraction line intensity of 2=10.70.3 in X-ray diffraction measurement is 0.20 or more and less than 0.58, and the catalyst having an active component represented by formula (A) shown below:

Mo.sub.10V.sub.aP.sub.bCu.sub.cAs.sub.dX.sub.eO.sub.g(A)

The invention relates to polyoxometalates represented by the formula (A.sub.n).sup.m+{M.sub.s[MM.sub.12X.sub.8O.sub.yR.sub.zH.sub.q]}.sup.m or solvates thereof, corresponding supported polyoxometalates, and processes for their preparation, as well as corresponding metal-clusters, optionally in the form of a dispersion in a liquid carrier medium or immobilized on a solid support, and processes for their preparation, as well as their use in reductive conversion of organic substrate.

The invention relates to polyoxometalates represented by the formula (A.sub.n).sup.m+{M.sub.s[MM.sub.12X.sub.8O.sub.yR.sub.zH.sub.q]}.sup.m or solvates thereof, corresponding supported polyoxometalates, and processes for their preparation, as well as corresponding metal-clusters, optionally in the form of a dispersion in a liquid carrier medium or immobilized on a solid support, and processes for their preparation, as well as their use in reductive conversion of organic substrate.