An olefin metathesis catalyst represented by Formula (I): wherein: M is ruthenium or osmium; X 1 and X 2 are independently halogen, trifluoroacetate, per-fluorophenols or nitrate; L 1 is a ligand represented by the structure of Formula (II), or is a N-Heterocyclic Carbene ligand represented by the structure of Formula (III): R 1 is unsubstituted saturated N-heterocycle, substituted saturated N-heterocycle, -NH(C 1 -C 24 alkyl), -N(C 1 -C 24 alkyl) 2 , -NH(C 5 -C 24 aryl), -N(C 5 -C 24 aryl) 2 , -N(C 1 -C 24 alkyl)(C 5 -C 24 aryl) or -N[(C 1 -C 6 alkylene) (C 5 -C 24 aryl)]2; R 2 is unsubstituted (C 5 -C 24 aryl), substituted (C 5 -C 24 aryl), unsubstituted saturated N-heterocycle, substituted saturated N-heterocycle, -NH(C 1 -C 24 alkyl), -N(C 1 -C 24 alkyl) 2 , -NH(C 5 -C 24 aryl), -N(C 5 -C 24 aryl) 2 , -N(C 1 -C 24 alkyl)(C 5 -C 24 aryl) or -N[(C 1 -C 6 alkylene)(C 5 -C 24 aryl)] 2 ; R 3 is unsubstituted (C 5 -C 24 aryl), substituted (C 5 -C 24 aryl), unsubstituted saturated N-heterocycle, or substituted saturated N-heterocycle; Y is CR 4 or N; R 4 is hydrogen, unsubstituted (C 1 -C 12 alkyl), or substituted (C 1 -C 12 alkyl); R 5 and R 6 are independently hydrogen, unsubstituted (C 5 -C 24 aryl), or substituted (C 5 -C 24 aryl); Q is a two-atom linkage represented by structures -[CR 7 R 8 ] s -[CR 9 R 10 ] t - or -[CR 11 =CR 12 ]-; R 7 , R 8 , R 9 and R 10 are independently hydrogen, unsubstituted (C 1 -C 24 alkyl), substituted (C 1 -C 24 alkyl), unsubstituted (C 5 -C 24 aryl), or substituted (C 5 -C 24 aryl); R 11 and R 12 are independently hydrogen, unsubstituted (C 1 -C 24 alkyl), substituted (C 1 -C 24 alkyl), unsubstituted (C 5 -C 24 aryl), or substituted (C 5 -C 24 aryl); and "s" and "t" are independently 1 or 2. M is ruthenium or osmium; X 1 and X 2 are independently halogen, trifluoroacetate, per-fluorophenols or nitrate; L 1 is a ligand represented by the structure of Formula (II), or is a N-Heterocyclic Carbene ligand represented by the structure of Formula (III): R 1 is unsubstituted saturated N-heterocycle, substituted saturated N-heterocycle, -NH(C 1 -C 24 alkyl), -N(C 1 -C 24 alkyl) 2 , -NH(C 5 -C 24 aryl), -N(C 5 -C 24 aryl) 2 , -N(C 1 -C 24 alkyl)(C 5 -C 24 aryl) or -N[(C 1 -C 6 alkylene) (C 5 -C 24 aryl)]2; R 2 is unsubstituted (C 5 -C 24 aryl), substituted (C 5 -C 24 aryl), unsubstituted saturated N-heterocycle, substituted saturated N-heterocycle, -NH(C 1 -C 24 alkyl), -N(C 1 -C 24 alkyl) 2 , -NH(C 5 -C 24 aryl), -N(C 5 -C 24 aryl) 2 , -N(C 1 -C 24 alkyl)(C 5 -C 24 aryl) or -N[(C 1 -C 6 alkylene)(C 5 -C 24 aryl)] 2 ; R 3 is unsubstituted (C 5 -C 24 aryl), substituted (C 5 -C 24 aryl), unsubstituted saturated N-heterocycle, or substituted saturated N-heterocycle; Y is CR 4 or N; R 4 is hydrogen, unsubstituted (C 1 -C 12 alkyl), or substituted (C 1 -C 12 alkyl); R 5 and R 6 are independently hydrogen, unsubstituted (C 5 -C 24 aryl), or substituted (C 5 -C 24 aryl); Q is a two-atom linkage represented by structures -[CR 7 R 8 ] s -[CR 9 R 10 ] t - or -[CR 11 =CR 12 ]-; R 7 , R 8 , R 9 and R 10 are independently hydrogen, unsubstituted (C 1 -C 24 alkyl), substituted (C 1 -C 24 alkyl), unsubstituted (C 5 -C 24 aryl), or substituted (C 5 -C 24 aryl); R 11 and R 12 are independently hydrogen, unsubstituted (C 1 -C 24 alkyl), substituted (C 1 -C 24 alkyl), unsubstituted (C 5 -C 24 aryl), or substituted (C 5 -C 24 aryl); and "s" and "t" are independently 1 or 2. <EOS>