NOVELTY - A metal based complex is new.    USE - New metal based complex for hydrogenation reaction and manufacture of partially or fully saturated compounds (all claimed).    ADVANTAGE - Polymer properties and polymer vulcanization behavior do not change.    DETAILED DESCRIPTION - A metal based complex of formula (I) is new.    M=Ru or Os;    Y=H, F, Cl, Br, I, CF3, pyridine, -OC6H5, CF3COO-, CH3SO3- or BF4;    R1-R4=H, NO2;    CF3, halo preferably F, Cl, Br, or I, optionally substituted 1-14C alkyl, preferably Me, Et, n-Pr, i-Pr, n-Bu, i-Bu or tert.-Bu, optionally substituted 3-10C cycloalkyl preferably cyclopentyl, cyclohexyl or cycloheptyl, optionally substituted 6-14C aryl preferably Ph, aryl, OR7, OC(=O)R7, CO(=O)R7, SO3R7, SO3N(R7)2 or SO3Na, or (N(R8)3)X when X is halide preferably Cl, optionally substituted 1-14C alkyl preferably Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, or tert.-Bu, optionally substituted 6-14C aryl preferably Ph or aryl, N(CH3)(C2H5)2+ Cl-, N(C2H5)2H+ Cl-, NH3+ Cl-, NH(CH3)2+ Cl- or N(CH3)3+ Cl-, tris-(1-6C-alkoxy)silyl-1-6C-alkyl, tris(6-14C-aryloxy)silyl-1-6C-alkyl, or tris(3-10C-cycloalkoxy)silyl-1-6C-alkyl, preferably trisethoxysilyl-n-propyl;    R7=H, optionally substituted alkyl, preferably Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, or tert.-Bu;    R8=H;    R5=H, optionally substituted 1-14C alkyl, preferably Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, or tert.-Bu, optionally substituted 3-10C cycloalkyl, preferably cyclopentyl, cyclohexyl or cycloheptyl, optionally substituted 6-14C aryl, preferably Ph or aryl which are located in o- and/or p-positions;    R6=optionally substituted 1-14C alkyl, preferably Me, Et, n-Pr, i-Pr, n-Bu, i-Bu or tert.-Bu or optionally substituted 3-10C cycloalkyl, preferably cyclopentyl, cyclohexyl or cycloheptyl, optionally substituted 6-14C aryl, preferably Ph or aryl; and    NHC=N-heterocyclic carbene ligand.    INDEPENDENT CLAIMS are included for:    (1) preparation of metal based complex;    (2) utilization of metal based complex for hydrogenation reactions; and    (3) manufacture of partially or fully saturated compound which involves contacting unsaturated compounds containing greater than or equal to 1 carbon-carbon double bonds, preferably terminal olefins, internal olefins, cyclic olefins, conjugated olefins, olefins having greater than or equal to 1 carbon-carbon double bond and additionally polar unsaturated double or triple bond, or oligomers or polymers having carbon-carbon double bonds, with hydrogen in the presence of greater than or equal to 1 metal based complex.