title: Rhodium hydride formation in the presence of a bulky monophosphite ligand: a spectroscopic and solid-state investigation.
abstract: A study has been carried out on rhodium catalyst preforming when modified with the bulky tris(2,4-di-tert-butylphenyl) phosphite, P(Obtbp)(3). X-Ray crystal structure determinations of a tropolone-type precursor complex [Rh(TropBr(3))(CO){P(Obtbp)(3)}].P(Obtbp)(3).CH(3)COCH(3)(TropBr(3)= 3,5,7-tribromotropolonate) and the free P(Obtbp)(3) ligand are reported. Systematic in situ IR and NMR studies of the particular rhodium phosphite modified catalyst and its precursors have led to the identification of two distinct rhodium hydride species. A {(1)H,(31)P} HMBC NMR experiment afforded clarity on the (31)P NMR spectra observed under hydroformylation conditions. The species were identified as [HRh(CO)(3){P(Obtbp)(3)}] and [HRh(CO)(2){P(Obtbp)(3)}(2)]. Attention was also given to the rate of catalyst formation when starting from different rhodium precursors.
authors.affiliation: Sasol Technology R & D, P.O. Box 1, Sasolburg 1947, South Africa. renier.crous@sasol.com
authors.forename: Renier
authors.initials: R
authors.lastname: Crous
authors.forename: Michael
authors.initials: M
authors.lastname: Datt
authors.forename: Douglas
authors.initials: D
authors.lastname: Foster
authors.forename: Linette
authors.initials: L
authors.lastname: Bennie
authors.forename: Casper
authors.initials: C
authors.lastname: Steenkamp
authors.forename: Johan
authors.initials: J
authors.lastname: Huyser
authors.forename: Leo
authors.initials: L
authors.lastname: Kirsten
authors.forename: Gideon
authors.initials: G
authors.lastname: Steyl
authors.forename: Andreas
authors.initials: A
authors.lastname: Roodt