CYLINDRICAL INTERNAL REFLECTANCE (CIR) EVIDENCE FOR THE FACILE FRAGMENTATION OF PHCCO3(CO)7(CIS-PH2PCH=CHPPH2) DURING THE HYDROFORMYLATION OF 1-PENTENE

The hydroformylation of 1-pentene has been examined with the catalyst precursor PhCCo3(CO)7(L-L) (where L-L = cis-Ph2PCH=CHPPh2) under mild batch conditions at 130-degrees-C and 600 psi H-2/CO (1:1). Extensive cluster fragmentation is observed at the end of the hydroformylation r eaction based on the isolation of the initially charged cluster in < 1 0% yield. Cylindrical internal reflectance (CIR) spectroscopy has been used to study the stability of the PhCCo3(CO)7(L-L) cluster and the n ature of cluster fragmentation species present in the working catalyst solution. Cluster fragmentation to [Co(CO)4]- occurs early in the rea ction prior to alkene hydroformylation, followed by the formation of t he phosphine-substituted complexes [Co(CO)3(L-L)]+ and [Co(CO)2(L-L)]- . The CIR data allow for the timing of the fragmentation of the cluste r to be assigned with confidence and support the batch reaction data r egarding the extensive fragmentation cluster observed. The effect of t he ancillary phosphine ligand on the stability of the initially charge d cluster is discussed and the CIR data is compared with the results o btained from the parent cluster PhCCo3(CO)9 under similar conditions.