SIMPLE KINETICS OF THE CATALYSIS OF THE HYDROFORMYLATION OF OLEFINS BY A RHODIUM PHOSPHANE COMPLEX - CATALYSIS OF THE HYDROFORMYLATION OF STYRENE BY THE RHODIUM-1,2,5-TRIPHENYL-H-PHOSPHOLE SYSTEM - KINETICALLYDEDUCED INVOLVEMENT OF A 14-ELECTRON BIS(1,2,5-TRIPHENYL-1H-PHOSPHOLE)RHODIUM INTERMEDIATE

The kinetics of the hydroformylation of styrene have been studied usin g the complex Rh(CO)Cl(TPP)(2) 4 (TPP = 1,2,5-triphenyl-1H-phosphole) as a catalyst precursor. This is one of the rare rhodium-based catalyt ic systems that is not sensitive to the phosphorus/rhodium ratio. The rate of hydroformylation was found to follow the expression R = K [sty rene][4]pH(2)pCO(-1), which is the first simple rate equation to be re ported for a rhodium phosphane catalyst. The reaction orders are consi stent with a mechanism including i) dissociation of carbon monoxide fr om a HRh(CO)(2)(TPP)(2) complex formed outside the catalytic cycle dur ing an induction period; ii) the involvement of a 14-electron acylrhod ium intermediate RCORh(TPP)(2) 10; and iii) a rate-determining step in volving oxidative addition of hydrogen to 10. The existence of a catal ytic intermediate such as 10 can be used to rationalize the results of the hydroformylation of functionalized olefins.