93254-01-4Relevant academic research and scientific papers
Ligand substitution processes in tetranuclear carbonyl clusters. 9. Reactions of Co4(CO)9(tripod), tripod = HC(PPh2)3, and its derivatives
Darensbourg, Donald J.,Zalewski, David J.
, p. 92 - 97 (1985)
Reactions of Co4(CO)9(tripod) with phosphorus donor ligands has resulted in a facile production of Co4(CO)8(L)(tripod) derivatives, where L = P(OMe)3, PMe3, and P(n-Bu)3. The reaction proceeds too rapidly to occur via a CO dissociative (D) mechanism and hence is ascribed to a ligand-dependent pathway (Ia) for CO substitution. Phosphorus ligand substitution occurs stereoselectively at the apical cobalt sites. Further substitution by nucleophilic PMe3 ligands leads first to additional apical incorporation of PMe3, followed by a subsequent slower process that results in ligand rearrangement to relieve steric crowding where both apical and radial sites are occupied by PMe3. A similar bis(phosphine) species is formed upon reaction of bis(diphenylphosphino)methane with Co4(CO)9(tripod). This derivative undergoes stereoselective carbonyl ligand exchange with 13CO at a rate which is not greatly different from the analogous process involving the parent compound Co4(CO)9(tripod). For example, the rate of dissociative CO loss in Co4(CO)7- (dppm) (tripod) is 5 times slower than the corresponding process in Co4(CO)9(tripod), indicative of only a slight perturbation in the reactivity of carbon monoxide at a cobalt center upon phosphine ligand substitution. A discussion of 13C and 31P NMR spectra of all the derivatives reported upon herein is included.
