Cobalt aminodiphosphine complexes as catalysts in the oxidation of n-octane

Abstract

Two types of cobalt aminodiphosphine complexes have been synthesized and characterized by IR spectroscopy, elemental analyses and single crystal X-ray diffraction. These are [Ph₂PN(R)PPh₂]CoCl₂, 1 and [Ph₂P(CH₂)₂N(R)(CH₂)₂PPh₂]CoCl₂, 2 where R = C₆H₁₁ (a); C₅H₁₁ (b); C₃H₇ (c). The functional groups on the nitrogen atom (R) were varied from a cyclohexyl ring, to n-pentyl alkyl chain, to an iso-propyl branched substituent. Complexes 2a and 2c were analyzed using single crystal X-ray diffraction. The geometry around the metal centers in 2a and 2c were distorted tetrahedral. All the complexes showed good activity as catalysts for the oxidation of n-octane using tert-butyl hydroperoxide (TBHP) as the oxidant. The complex bearing the flexible ligand backbone with the cyclohexyl substituent on the nitrogen atom was the most active and showed high selectivity towards ketones with 2-octanone being the dominant product.