CHEMISTRY OF DICOBALT OCTACARBONYL ON ZINC-OXIDE - HOMONUCLEAR ION-PAIRING SURFACE SPECIES-RELATED TO CATALYTIC ACTIVITY IN ETHYLENE HYDROFORMYLATION

The reaction of Co-2(CO)(8) with partially hydroxylated ZnO has been studied. Formation of Co-4(CO)(12) deposited on the surface, and disproportionation of Co-2(CO)(8) to Co-2(+) and [Co(CO)(4)](-) has been evidenced. [Co(CO)(4)](-) has been characterized on the surface by in situ FTIR spectroscopy. Co2+ and [Co(CO)(4)](-) were extracted from the surface with [PPN]Cl. Chemisorption of [PPN] [Co(CO)(4)] on the surface, in presence or not of Co2+ ions, suggests that, when Co,(CO), reacts with ZnO, Co2+/[Co(CO)(4)](-) homonuclear ion-pairing species on the surface are produced. This supported molecular species is related to the catalytic activity in ethylene hydroformylation with high selectivity to propanal production.