Phosphite modified cobalt complexes for olefin hydroformylation

Abstract

English: Several dinuclear complexes of the form [Co2(CO)6L2] with L being an aromatic phosphite ligand were varied as follows: L = P(OPh)3, P(O-4-tBuC6H4)3, P(O-2- tBuC6H4)3, P(O-2-EtC6H4)3, P(O-2-iPrC6H4)3. These dinuclear complexes have been synthesised and characterized by IR and NMR. The dinuclear complexes which were successful in being characterized by X ray crystallography were the ones with L = P(O-4-tBuC6H4)3 and P(O-2-EtC6H4)3. These two dinuclear complexes including the complex with P(OPh)3 as a ligand were used as precursors as active catalysts in the hydroformylation of 1-octene. High pressure spectroscopy was used to detect hydride intermediates. High pressure infra red (HP-IR) studies revealed the formation the monophosphite hydrides ([HCo(CO)3L]) for all the studied ligands, as well as the formation of bisphosphite hydrides [HCo(CO)2L2] and the unmodified hydride [HCo(CO)4]. At 140 °C both the unmodified and the bisphosphite had disappeared and the only specie present was the monophosphite hydride which is the active hydride catalyst in hydroformylation reactions. This study has proven the importance of the stability of the hydride in the hydroformylation reaction along with the selectivity and conversion rate of the 1- octene to the aldehyde. The stability of the hydride was tested in the presence of 1- octene and in the absence of 1-octene. Catalytic activity of the studied cobalt phosphite complexes was tested at the end of the stability runs.

Afrikaans: ‘n Aantal bikernige bis-metaal komplekse met die algemene vorm [Co2(CO)6L2] is gesintetiseer, waar L aromatiese fosfiete is wat as volg gevariëer is: L = P(OPh)3, P(O-4-tBuC6H4)3, P(O-2-tBuC6H4)3, P(O-2-EtC6H4)3, P(O-2-iPrC6H4)3. Hierdie komplekse is gesintetiseer en gekarakteriseer deur IR en KMR. Die bikernige komplekse wat suksesvol deur X-straal kristallografie gekarakteriseer was die met L = P(O-4-tBuC6H4)3 en P(O-2-EtC6H4)3. Hierdie twee bikernige komplekse, insluitend die kompleks met P(OPh)3 as ligand, was gebruik as voorgangers in die hidroformilering van 1-okteen. Hoë-druk spektroskopie was gebruik om die hidried tussengangers spesies op te spoor. Hoë-druk infra-rooi (HD-IR) studies het die forming van mono-fosfiet hidried ([HCo(CO)3L]) aangedui vir all die bestudeerde ligande, ek ook vir die vorming van bisfosfiet hidriede ([HCo(CO)2L2]) en die ongemodifiseerde hidried [HCo(CO)4]. By 140 ˚C het beide die ongemodifiseerde en die bisfosfiet spesies verdwyn en die enigste spesie teenwoordig was die monofosfiet hidried wat die aktiewe hidried katalis is in die hidroformileerings reaksies. Hierdie studie het die belangrikheid van die stabiliteit van die hidried in die hidroformilerings reaksie bewys saam met die selektiwiteit en omskakelings tempo van 1-okteen na die aldehied. Die stabiliteit van die hidried was getoets in die teenwoordigheid van 1-okteen en in die afwesigheid van 1-okteen. Katalitiese aktiwiteit van die gestudeerde kobalt fosfiet komplekse was getoets na die stabiliteits lopies.