Nitrene transfer reactions by late transition metal complexes

Abstract

This thesis presents nitrene transfer reactions that are catalyzed or mediated by late transition metal complexes. Sterically large, fluorinated supporting ligands are used to minimize potential side reactions. A new 1,10-phenanthroline ligand has been synthesized with 2,4,6-(CF3)3C6H2- groups in the 2- and 9-positions (1). A cationic copper(l) complex of 1 catalyzes nitrene transfer from N-(p-toluenesulfonylimino)phenyliodinane (PhlNTs) to the C-H bonds of 1,3-dimethoxybenzene in 63% yield. Altering the stoichiometry results in the formation of a different major product, N,N-bis(2',4'-dimethoxyphenyl)-p-toluenesulfonamide, in 33% yield. Treatment of a cationic copper(l) complex of 1 with p-nitrobenzenesulfonyl azide (NsN3) results in the formation of a rare mononuclear sulfonamido complex of copper(ll), 2. This complex is presumably formed via decomposition of a reactive sulfonimido complex of copper(lll). Although not a proficient nitrene transfer reagent to benzene, complex 2 is a precatalyst for nitrene transfer from NsN3 to benzene. Deprotonation of a palladium(ll) sulfonamido complex of 1 results in the formation of the first mononuclear sulfonimido complex of palladium,

(cont.) 3. The sulfonimido ligand is bound in a K2-N,O chelate. This complex is a proficient nitrene transfer reagent to carbon monoxide, phosphines, and ethyl vinyl ether. A rhodium(lll) hydride chloride complex containing two N-heterocyclic carbene ligands, one of which is cyclometallated, is a convenient synthetic equivalent of a rhodium(l) chloride complex. Treatment of the rhodium(Ill) hydride with acetonitrile results in reductive elimination to form a rhodium(l) chloride complex. The chloride is readily abstracted by sodium azide to form a cationic rhodium(l) complex coordinated by two molecules of acetonitrile and containing an unbound azide. Upon exposure to UV light, this molecule undergoes cyclometallation to form a cationic rhodium(lll) hydride complex. The rhodium(lll) hydride chloride complex can be treated with oxygen to form a rhodium(lll) peroxide complex. The neutral peroxide complex has poor reactivity with trimethylphosphite and t-stilbene. However, a cationic rhodium peroxide complex oxidizes trimethylphosphite and t-stilbene at elevated temperatures.