Kinetic studies have been carried out for the formation of vinylideneruthenium(II) complexes RuCl 2 { C C(Z)R}(dcpmp) [Z = H, R = p -MeOC 6 H 4 ( 2a ), p -MeC 6 H 4 ( 2b ), Ph ( 2c ), p -BrC 6 H 4 ( 2d ), t -Bu ( 2e ), ferrocenyl ( 2f ); Z = SiMe 3, R = Ph ( 5a ), SiMe 3 ( 5b ); dcpmp = 2,6-bis{(dicyclohexylphosphino)methyl}pyridine] from RuCl 2 (NCMe)(dcpmp) ( 1 ) and alkynes (RC⋮CZ). The reactions with terminal alkynes proceed via preliminary dissociation of the MeCN ligand from 1, giving vinylidene complexes 2a − 2f in quantitative yields. More electron-rich and less sterically demanding alkynes tend to provide higher reaction rates. On the other hand, the reactions with silylalkynes afford equilibrium mixtures of 1 and β-silylvinylidene complexes 5 . The X-ray structures of 2c and 5a are reported.
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Katayama et al. (2002) studied this question.