REACTIVITY STUDIES OF ETA(2)-ACYL COMPLEXES OF MOLYBDENUM - KINETICS OF ETA(2)-ACYL TO ETA(2)-IMINOACYL ISOMERIZATION IN THEIR REACTIONS WITH ISOCYANIDES

Treatment of the dihaptoacyls [Mo{eta(2)-C(O)R}L(CO)(PMe(3))(2)] with carbon monoxide afforded the dicarbonyl derivatives [Mo{eta(2)-C(O)R}L (CO)(2)(PMe(3))][L=H2B(pz)(2) or H2B(dmpz),; pz=pyrazolyl, dmpz=3,5-di methylpyrazolyl; R=Me, CH(2)SiMe(3) or CH(2)CMe(3)]. The analogous rea ctions with isocyanides, CNR', yielded two types of products, namely t he acyl-isocyanides [Mo(eta(2)-C(O)R}L(CO)(CNR')(Me(3))] or the eta(2) -iminoacyls [Mo{eta(2)-C(NR')R}L(CO)(2)(PMe(3))] (R'=CNC(6)H(3)Me-2,6, CNC(6)H(4)OMe-p, CNCH(2)Ph or CNC6H11) depending upon the nature of th e bis(pyrazolyl)borate ligand and the R group. Kinetic studies of the transformation )-C(NR')CH2-SiMe(3)}{H2B(dmpz)(2)}(CO)(2)(PMe(3))] (R'= 2,6-Me(2)C(6)H(3)) show first-order behaviour and are consistent with a mechanism involving deinsertion of CO to give a seven-co-ordinate al kyl intermediate in the rate-determining step.