Control of the reactivity of trans-[Mo2(cp)2(CO)(YZ)(μ -SR)2] (cp = η-C5H5; YZ = CO or CN−) by the sulfur substituents (R = Me, Pri, But, Ph or CF3). Crystal structure of trans-[Mo2(cp)2(CO)(CNMe)(μ- SCF3)2]

Abstract

Reaction of trans-[Mo 2 (cp) 2 (CO) 2 (µ-SR) 2 ] (cp = η-C 5 H 5 ; R = Me, Pr i , Bu t , Ph or CF 3 ; syn and anti isomers) with cyanide ion gave the corresponding cyanide complexes trans-[Mo 2 (cp) 2 (CO)(CN)(µ-SR) 2 ] - , except with R = Bu t where no reaction was observed. For R = CF 3 , two isomers having a syn orientation of the sulfur substituents were obtained. The nature of the R groups is shown to have a crucial influence on the site of the reaction of the cyanide complexes with Me 3 O + . Complexes where R = Me, Pr i (syn and anti isomers) or Ph (anti isomer) were S-methylated, whereas N-methylation was observed for R = Ph (syn isomer) or CF 3 (anti and both syn isomers). This is ascribed to electronic effects of the R groups which control the site of methylation by switching the reaction from orbital control (S-methylation) to charge control (N-methylation). For R = CF 3 , the R groups also affect the reaction of the dicarbonyl precursor with a YZ substrate since the preferred site of attack is different for YZ = CN - and YZ = RNC.