Reactions of transition-metal carbonyls with organolithium compounds. III. Synthesis of tetracarbonyl (tertiary phosphite) oxy- and amino-carbene complexes of the group VIB metals

Abstract

Compounds of the general composition M(CO) 4(P(OCH 2) 3CC 2H 5)C(OC 2H 5)R have been synthesized by the reaction of organolithium reagents with M(CO) 5P(OCH 2) 3CC 2H 5 under mild conditions, where M = Cr, Mo, W; and R = CH 3, C 6H 5. Aminolysis of these compounds at −70°C with ammonia and cyclohexylamine have led to the preparation of M(CO) 4(P(OCH 2) 3CC 2H 5)C(NHR′)R species, where M = Cr, Mo, W; R = CH 3, C 6H 5; and R′ = H, C 6H 11. Infrared and proton nuclear magnetic resonance studies have been carried out on these compounds. These carbene complexes have exclusively cis structures with respect to the metal, with the lone exception Cr(CO) 4(P(OCH 2) 3CC 2H 5)C(OC 2H 5)C 6H 5, which exists in both cis and trans isomeric forms. The significance of these stereochemical observations is discussed in terms of the steric and electronic effects involved in the nucleophilic addition reactions of the organolithium reagents with bound carbon monoxide ligands.