ИСТИНА

Ion pairing with cations has a marked but nonuniform effect in the chemistry of carbonylmetallate anions, and can either inhibit or facilitate their reactions.1,2 We have studied the effect of cation solvating additives (18-crown-6, HMPA) in the reactions of carbonylmetallates [M’]+[M(CO)nL]- with vinyl halides activated by strong EWG-groups, which at the same time can serve as hard donor centers for Na or K cations. In the reactions of Na[Re(CO)5] and K[Mn(CO)5] with these vinyl chlorides, separation of carbonylmetallate ion pairs upon the addition of 18-crown-6 to the THF solution decreases the reaction rate. Reactions with -cyanovinyl chlorides, PhCCl=C(CN)2 and Z-PhC(CN)=CHCl, are slowed down by a factor of 4 - 17, but the effect is most pronounced for vinyl chlorides activated by carbonyl groups, PhCCl=C(CO2Et)2 and E-ClCH=CHCO2Me, which slow down by a factor of 80 - 200. These strong cation assistance effects are contrasted by “normal” effects observed for the reaction of K[Mn(CO)5] with 1-chloro-2-methyl perfluoro¬cyclopentene, accelerated by [2.2.2]-cryptand, as well as for the other fluorine-activated vinyl halides studied previously.