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Bicyclic phosphines as ligands for cobalt-catalysed hydroformylation

2003; Royal Society of Chemistry; Issue: 10 Linguagem: Inglês

10.1039/b210650g

1477-9234

Chantelle Crause, Linette Bennie, L. Damoense, Catherine L. Dwyer, Cronjé Grové, Neil E. Grimmer, Werner Janse van Rensburg, Megan M. Kirk, Konrad M. Mokheseng, Stefanus Otto, Petrus J. Steynberg,

Cyclopropane Reaction Mechanisms

A range of tertiary phosphine ligands derived from (R)-(+)-limonene was studied by HP-31P NMR, HP-IR, batch autoclave reactions and molecular modelling during the hydroformylation of 1-dodecene using a cobalt catalyst system and a metal ∶ ligand ratio of 1 ∶ 2. The phosphorus atom was incorporated in a limonene bicycle where the third substituent was systematically varied, Lim-R (R = (CH2)17CH3, (CH2)9CH3, (CH2)4CH3, (CH2)3CH3, (CH2)3C6H5, (CH2)3CN, (CH2)3OCH2C6H5, (CH2)2OCH2CH3). The activity and selectivity was, to a large extent, governed by the equilibria between the modified and unmodified cobalt catalytic species in the reaction. Linearity ranged from 54 to 71% with Lim-(CH2)3CN yielding the most branched product and Lim-(CH2)4CH3 the most linear product. The n ∶ iso ratio (ratio of linear to 2-methyl branched alcohol) also followed the same trend with a ratio of 2.6 for Lim-(CH2)3CN and 4.9 for Lim-(CH2)4CH3. The rate decreased as the linearity increased with pseudo k values of 0.5 to 1.1. Hydrogenation of the alkene varied within a narrow band from 5–6%.