(TRIPHENYLCYCLOPROPENYL)NICKEL DERIVATIVES AS CATALYSTS FOR THE ISOMERIZATION OF QUADRICYCLANE TO NORBORNADIENE

Infrared spectroscopy indicates that the (triphenylcyclopropenyl)nickel complex (C6H5)3C3Ni(CO)Cl readily loses its CO ligand in solution at room temperature but reacts with CO at room temperature and atmospheric pressure to form successively (C6H3)3C3Ni(CO)2Cl and Ni(CO)4. Reactions of (C6H5)3C3Ni(CO)Cl with various ligands in solution at room temperature rapidly give complexes with a L:Ni ratio of 2:1 of the type (C6H5)3C3NiL2Cl (L=tetrahydrofuran, 2, 2'-bipyridyl, (C6H5)2PCH3, (C6H5)2PC1, C6H5PC12, and P(OR)3 (R=phenyl, isopropyl, and methyl)). The ligand (C6H5)2PCH3 also gives an isolable 1:1 L-Ni complex of the stoichiometry (C6H5)3C3Ni[P(C6H5)2CH3]Cl. The complex (C6H5)3C3Ni(CO)Cl is an active catalyst for the isomerization of quadricyclane to norbornadiene under conditions where it is converted to a carbonyl-free complex. Addition of the ligands L to (C6H5)3C3Ni(CO)Cl in L:Ni ratios from 1:1 to 3:1 gradually reduces the catalytic activity of these systems. The catalytic activities of the (C6H5)3C NiL2Cl derivatives (L=trivalent phosphorus ligand) increase as the coordination chemical shift decreases in their phosphorus-31 NMR spectra. © 1979, American Chemical Society. All rights reserved.