Nitrosyl Complexes in Homogeneous Catalysis

In this chapter the application of transition metal nitrosyl complexes in homogeneous catalysis has been reviewed. Particular attention was paid to the function of nitrosyl as: (1) a pi-accepting ancillary ligand; (2) a non-innocent ligand capable of reversible linear/bent transformations triggering catalytic reaction courses; (3) a redox-active ligand functioning as a "nitrosyl/nitro" redox couple for oxygen atom transfer reactions. The catalytic performance and the reaction mechanisms are discussed in terms of the respective function of the NO ligand. Group 6 molybdenum and tungsten mononitrosyl hydride complexes are reviewed with respect to their activity in hydrogenations proceeding with heterolytic splitting of H-2. Group 7 rhenium mononitrosyl and dinitrosyl hydride complexes are reviewed with respect to their highly efficient performance in hydrogen-related catalyses, which is highlighted by alkene hydrogenations based on Re(I) mononitrosyl complexes and efficient transfer hydrogenations based on bifunctional Shvo-type Re-H/OH and Noyori-type Re-H/NH complexes. Group 8 iron mononitrosyl- and dinitrosyl-based catalysts are surveyed with respect to their function as Lewis acids inducing nucleophilic activity in Lewis acid type organic transformations. Then the "catalytic nitrosyl effect" is described boosting catalyses by reversible nitrosyl bending, which plays a crucial role in Re(-I) dinitrosyl and Re(I) mononitrosyl catalytic systems. The oxygen atom transfer reaction based on the "nitrosyl/nitro" redox couple involving the Co, Pd, Rh, and Ru metal centers was also reviewed.