A neutral or cationic mononuclear ruthenium divalent complex represented by formula (1) can actualize exceptional catalytic activity in at least one reaction among a hydrosilylation reaction, hydrogenation reaction, and carbonyl compound reduction reaction. (In the formula, R1-R6 each independently represent a hydrogen atom or an alkyl group, aryl group, aralkyl group, organooxy group, monoorganoamino group, diorganoamino group, monoorganophosphino group, diorganophosphino group, monoorganosilyl group, diorganosilyl group, triorganosilyl group, or organothio group optionally substituted by X; at least one pair comprising any of R1-R3 and any of R4-R6 together represents a crosslinkable substituent; X represents a halogen atom, organooxy group, monoorganoamino group, diorganoamino group, or organothio group; L each independently represent a two-electron ligand other than CO and thiourea ligands; two L may bond to each other; and m represents an integer of 3 or 4.)