A method of synthesis of a product complex, comprising: subjecting a precursor complex to reaction with an alkylating agent; wherein the product complex has a structure of formula 15 in which L 1' and L 2' are, independently, inert ligands, wherein L 1' comprises a quaternary ammonium group or a phosphonium group; and M is ruthenium or osmium; and X, X 1, and each X 2 are, independently, anionic ligands; and wherein the alkylating agent has a formula R 8 X 2, wherein_R 8 is optionally substituted -C1-20 alkyl, optionally substituted -C 3-8 cycloalkyl, optionally substituted -C 2-20 alkenyl, or optionally substituted -C 2-20 alkynyl, wherein each substituent is independently a halogen atom, -C 5-10 aryl, -C(=O)-C 1-6 alkyl, -C(=O)-O-C 1-6 alkyl, -C(=O)-N(C 1-6 alkyl) 2, -C(=O)-NH(C 1-6 alkyl)-O-C 1-6 alkyl, -C(=O)-C 5-10 aryl, -C(=O)-O-C 5-10 aryl, -C(=O)-N(C 5-10 aryl) 2, or -C(=O)-NH(C 5-10 aryl)-O-C 5-10 aryl; and X 2 is an anionic ligand; R 17' is H, an optionally substituted -C 2-20 alkenyl, an optionally substituted -C 2-20 alkynyl or an optionally substituted -C 5-10 aryl; and R 18' is an optionally substituted phenyl or vinyl substituent; a is 1, 2, 3, 4, 5, 6 or 7; z is 1, 2, 3, 4, 5, 6 or 7; wherein the precursor complex has a structure of formula 10 in which M, X, X 1 have the same meaning as in formula 15; R 17 is H, an optionally substituted -C 2-20 alkenyl, an optionally substituted -C 2-20 alkynyl or an optionally substituted -C 5-10 aryl; L 1 and L 2 are independently inert ligands, wherein L 1 comprises an alkylamino group, or an alkylphosphine group; and R 18 is optionally substituted phenyl, wherein R 18, together with the carbon atom of the metal carbene connecting it, may be optionally linked to L 2 _to form a bidentate ligand. subjecting a precursor complex to reaction with an alkylating agent; wherein the product complex has a structure of formula 15 in which L 1' and L 2' are, independently, inert ligands, wherein L 1' comprises a quaternary ammonium group or a phosphonium group; and M is ruthenium or osmium; and X, X 1, and each X 2 are, independently, anionic ligands; and wherein the alkylating agent has a formula R 8 X 2, wherein_R 8 is optionally substituted -C1-20 alkyl, optionally substituted -C 3-8 cycloalkyl, optionally substituted -C 2-20 alkenyl, or optionally substituted -C 2-20 alkynyl, wherein each substituent is independently a halogen atom, -C 5-10 aryl, -C(=O)-C 1-6 alkyl, -C(=O)-O-C 1-6 alkyl, -C(=O)-N(C 1-6 alkyl) 2, -C(=O)-NH(C 1-6 alkyl)-O-C 1-6 alkyl, -C(=O)-C 5-10 aryl, -C(=O)-O-C 5-10 aryl, -C(=O)-N(C 5-10 aryl) 2, or -C(=O)-NH(C 5-10 aryl)-O-C 5-10 aryl; and X 2 is an anionic ligand; R 17' is H, an optionally substituted -C 2-20 alkenyl, an optionally substituted -C 2-20 alkynyl or an optionally substituted -C 5-10 aryl; and R 18' is an optionally substituted phenyl or vinyl substituent; a is 1, 2, 3, 4, 5, 6 or 7; z is 1, 2, 3, 4, 5, 6 or 7; in which L 1' and L 2' are, independently, inert ligands, wherein L 1' comprises a quaternary ammonium group or a phosphonium group; and M is ruthenium or osmium; and X, X 1, and each X 2 are, independently, anionic ligands; and wherein the alkylating agent has a formula R 8 X 2, wherein_R 8 is optionally substituted -C1-20 alkyl, optionally substituted -C 3-8 cycloalkyl, optionally substituted -C 2-20 alkenyl, or optionally substituted -C 2-20 alkynyl, wherein each substituent is independently a halogen atom, -C 5-10 aryl, -C(=O)-C 1-6 alkyl, -C(=O)-O-C 1-6 alkyl, -C(=O)-N(C 1-6 alkyl) 2, -C(=O)-NH(C 1-6 alkyl)-O-C 1-6 alkyl, -C(=O)-C 5-10 aryl, -C(=O)-O-C 5-10 aryl, -C(=O)-N(C 5-10 aryl) 2, or -C(=O)-NH(C 5-10 aryl)-O-C 5-10 aryl; and X 2 is an anionic ligand; R 17' is H, an optionally substituted -C 2-20 alkenyl, an optionally substituted -C 2-20 alkynyl or an optionally substituted -C 5-10 aryl; and R 18' is an optionally substituted phenyl or vinyl substituent; a is 1, 2, 3, 4, 5, 6 or 7; z is 1, 2, 3, 4, 5, 6 or 7; wherein the precursor complex has a structure of formula 10 in which M, X, X 1 have the same meaning as in formula 15; R 17 is H, an optionally substituted -C 2-20 alkenyl, an optionally substituted -C 2-20 alkynyl or an optionally substituted -C 5-10 aryl; L 1 and L 2 are independently inert ligands, wherein L 1 comprises an alkylamino group, or an alkylphosphine group; and R 18 is optionally substituted phenyl, wherein R 18, together with the carbon atom of the metal carbene connecting it, may be optionally linked to L 2 _to form a bidentate ligand. in which M, X, X 1 have the same meaning as in formula 15; R 17 is H, an optionally substituted -C 2-20 alkenyl, an optionally substituted -C 2-20 alkynyl or an optionally substituted -C 5-10 aryl; L 1 and L 2 are independently inert ligands, wherein L 1 comprises an alkylamino group, or an alkylphosphine group; and R 18 is optionally substituted phenyl, wherein R 18, together with the carbon atom of the metal carbene connecting it, may be optionally linked to L 2 _to form a bidentate ligand.