TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The metal atom includes lanthanides, actinides, or transition metal from Group 2-12 preferably 3-6 of the periodic table of elements.It preferably comprises scandium, yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cerium, or neodymium.The solid support includes oxides, sulfide, and/or azides.It may includes atom M consisting of magnesium, titanium, zirconium, cerium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, boron, aluminum, gallium, silicon, germanium, phosphorus, or bismuth; and atom X consisting of oxygen, sulfur or nitrogen.The metal atom (ME) is present in the supported metal compound in the form of (A) that corresponds to a formula (support(M,X)M-Xi)xi-Me-Ry (I); and in form (B) that corresponds to formula (support(M,X)M-Xj)xj-Me (II) and/or optionally (support(M,X)M-Xk)xk-Me-Qz (III).Q = neither a hydrogen atom nor a hydrocarbon radical but preferably an atom of an element from Groups 15-1;xi, y = integers that are identical or different at least 1;(xi+y) = less than or equal to the degree of oxidation of the Me in formula (I);xj = at least 1 and less than of equal to the degree of oxidation of Me in formula (II);xk, z = integers that are identical or different and is at least 1;(xk+z) = less than or equal to the degree of oxidation of Me in formula (III).The degrees of oxidation of Me in formulae (I-III) are identical or different.Preferred Property: The metal atoms (Me), correspond to identical or different metals for each forms of (A) and (B).It is bonded to the support and to a hydrogen atom and/or to a saturated or unsaturated hydrocarbon radical having 1-20 C atoms.It may be bonded solely to the support to the elements of Group 15-17 that is alone or itself bonded to the hydrogen and/or to the hydrocarbon radical and/or to a silylated or organosilylated group.Preferred Composition: The supported metal comprises (per 100 mol of Me) 5-95 preferably 20-90 mol me in the form (A), and 95-5 preferably 80-10 mol Me in the form (B). EXAMPLE - A 1 g silica partially dehydroxylated at 700 degrees C, 5 ml of n-pentane, and a solution of 15 ml of n-pentane comprising 64 mg tantalum precursor correspond to (Ta(CH2C(CH3)3)3(=CHC(CH3)3) were introduced into a glass reactor at 20 degrees C. The mixture was stirred for 30 minutes and n-pentane was evaporated. The solid compound thus grafted was vacuum and treated at 80 kPa of hydrogen at 500 degrees C for 15 hours. The reactor was cooled to 20 degrees C and gas phase was discharged. 0.8 g of solid compound was recovered and suspended in 20 ml of n-pentane. A solution of 10 ml n-pentane comprising 100 mg tantalum precursor (same as above) was added to the suspension. After 2 hours, the resulting solid was filtered, washed 5 times with 10 ml n-pentane, and dried under vacuum. 0.75 g solid compound was recovered and contacted with an atmosphere of 80 kPa of hydrogen. The reactor was heated to 150 degrees C for 12 hours. It was cooled to 20 degrees C and the gas phase was discharged to isolate and recover a supported tantalum compound comprising both form (A) (support(Si,O)Si-O)2Ta-H, and form (B) (support(Si,O)Si-O)3-Ta.