| abstract |
A catalyst system includes a complex having formula I which advantageously has a sterically protecting N-heterocyclic carbene (NHC) carbene-pyridine ligand to handle harsh reactions conditions than many prior art catalysts: n n n n n n n n n n wherein M is a transition metal; o is 0, 1, 2, 3, or 4; R 1 is a C 1-6 alkyl, a C 6-18 aryl, or an optionally substituted C 5-18 heteroaryl. In a refinement, R 1 is methyl, ethyl, butyl, n-propyl, isopropyl, n-butyl, sec-butyl, or t-butyl; R 2 , R 3 , R 3 ′ are independently an optionally substituted C 1-6 alkyl, halo (e.g., Cl, F, Br, etc), NO 2 , an optionally substituted C 6-18 aryl, or an optionally substituted C 5-18 heteroaryl; R 4 , R 4 ′ are independently an optionally substituted C 1-6 alkyl, halo, NO 2 , an optionally substituted C 6-18 aryl, or an optionally substituted C 5-18 heteroaryl; and X − is a negatively charge counter ion and L 1 , L 2 are each independently a neutral ligand. |