Synthesis,crystal structure and hydroformylation activity of triphenylphosphite modified cobalt catalysts

摘要

The dinuclear complex[Co_2(CO)_6{P(OPh)_3}_2](2)has been synthesised and was fully characterised.The solid state structure revealed a trans diaxial geometry,no bridging carbonyls,and Co-Co and Co-P bond lengths of 2.6722(4)and 2.1224(4)A,respectively.Catalysed hydroformylation of 1-pentene with 2 was attempted at temperatures in the range 120 to 210 degC and pressures between 34 and 80 bar.High pressure spectroscopy(HP-IR and HP-NMR)was used to detect hydride intermediates.High pressure infrared(HP-IR)studies revealed the formation of[HCo(CO)_3P(OPh)_3](4)at ca.110 degC,but at higher temperatures absorption bands corresponding to[HCo(CO)_4](3)were observed.The hy.dride intermediate 4 has also been synthesised and characterised.Upon increased ligand concentration,HP-IR studies showed the formation of new carbonyl absorption bands due to a higher substituted cobalt carbonyl complex-[HCo(CO)_2{P(OPh)_3}_2](5),which is believed to be catalytically less active.Complex 5 has been synthesised independently and was fully characterised.A low temperature crystal structural study of 5 revealed a trigonal bipyramidal structure with a trans H-Co-CO arrangement and two equatorial phosphite ligands,the Co-P bond lengths being 2.1093(8)and 2.1076(8)A,respectively.