A neutral or cationic mononuclear divalent ruthenium complex of formula wherein each of R 1 to R 6 independently is - a hydrogen atom, - an alkyl, aryl or aralkyl group, - an organooxy group of the formula RO where R is a substituted or unsubstituted alkyl group of 1 to 30 carbon atoms, aryl group of 6 to 30 carbon atoms or aralkyl group of 7 to 30 carbon atoms, - a monoorganoamino group of the formula RNH 2 where R is as defined above, - a diorganoamino group of the formula R 2 NH where each R independently is as defined above, - a monoorganophosphino group of the formula RPH where R is as defined above, - a diorganophosphino group of the formula R 2 P where each R independently is as defined above, - a monoorganosilyl group of the formula RSiH 2 where R is as defined above, - a diorganosilyl group of the formula R 2 SiH where each R independently is as defined above, - a triorganosilyl group of the formula R 3 Si where each R independently is as defined above, or - an organothio group of the formula RS where R is as defined above, wherein said groups for R 1 to R 6 may be substituted with X, and at least one pair of any of R 1 to R 3 with any of R 4 to R 6, taken together, may represent a crosslinking substituent, X is a halogen atom, an organooxy group as defined above, a monoorganoamino group as defined above, a diorganoamino group as defined above or an organothio group as defined above;; each L 1 is a two-electron ligand selected from isonitriles, nitrogen-containing heterocycles and phosphites, with the proviso that the two L 1 ligands may be bonded to one another; each L 2 is a triorganohydrosilane two-electron ligand, with the proviso that the two L 2 ligands may be bonded to one another, and m 1 and m 2 are both 2. - a hydrogen atom, - an alkyl, aryl or aralkyl group, - an organooxy group of the formula RO where R is a substituted or unsubstituted alkyl group of 1 to 30 carbon atoms, aryl group of 6 to 30 carbon atoms or aralkyl group of 7 to 30 carbon atoms, - a monoorganoamino group of the formula RNH 2 where R is as defined above, - a diorganoamino group of the formula R 2 NH where each R independently is as defined above, - a monoorganophosphino group of the formula RPH where R is as defined above, - a diorganophosphino group of the formula R 2 P where each R independently is as defined above, - a monoorganosilyl group of the formula RSiH 2 where R is as defined above, - a diorganosilyl group of the formula R 2 SiH where each R independently is as defined above, - a triorganosilyl group of the formula R 3 Si where each R independently is as defined above, or - an organothio group of the formula RS where R is as defined above, wherein said groups for R 1 to R 6 may be substituted with X, and at least one pair of any of R 1 to R 3 with any of R 4 to R 6, taken together, may represent a crosslinking substituent, X is a halogen atom, an organooxy group as defined above, a monoorganoamino group as defined above, a diorganoamino group as defined above or an organothio group as defined above;; each L 1 is a two-electron ligand selected from isonitriles, nitrogen-containing heterocycles and phosphites, with the proviso that the two L 1 ligands may be bonded to one another; each L 2 is a triorganohydrosilane two-electron ligand, with the proviso that the two L 2 ligands may be bonded to one another, and m 1 and m 2 are both 2. wherein said groups for R 1 to R 6 may be substituted with X, and at least one pair of any of R 1 to R 3 with any of R 4 to R 6, taken together, may represent a crosslinking substituent, X is a halogen atom, an organooxy group as defined above, a monoorganoamino group as defined above, a diorganoamino group as defined above or an organothio group as defined above;; each L 1 is a two-electron ligand selected from isonitriles, nitrogen-containing heterocycles and phosphites, with the proviso that the two L 1 ligands may be bonded to one another; each L 2 is a triorganohydrosilane two-electron ligand, with the proviso that the two L 2 ligands may be bonded to one another, and m 1 and m 2 are both 2.