Activation of Molecular Hydrogen and Oxygen by PSiP Complexes of Cobalt. Issue 40 (15th October 2018)

• Record Type: Journal Article
• Authors: Murphy, Luke J.; Ruddy, Adam J.; McDonald, Robert; Ferguson, Michael J.; Turculet, Laura
• Is Part Of: European journal of inorganic chemistry. Issue 40(2018)
• Page Start: 4481
• Page End: 4493
• Publication Date: 2018-10-15
• Subjects: Bond activation -- Cobalt -- Hydrogen -- Oxygen -- Pincer -- Silyl compounds; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201800915
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : The syntheses of Co II halide complexes supported by κ 3 ‐(2‐Cy2 PC6 H4 )2 SiMe (Cy‐PSiP) ligation are detailed. Reduction of (Cy‐PSiP)Co(PMe3 )I could be achieved under mild conditions using magnesium metal to generate the Co I complex (Cy‐PSiP)Co(PMe3 )N2 in high yield. When this reaction was carried out under an atmosphere of CO, (Cy‐PSiP)Co(CO)2 was obtained. Unlike the facile reduction of Co II to Co I, attempts to access Co III species supported by Cy‐PSiP ligation proved challenging. Attempted oxidative addition reactions involving (Cy‐PSiP)Co(PMe3 )N2 were generally unsuccessful, with the sole exception of H2, which reacted to afford the dihydride complex (Cy‐PSiP)Co(PMe3 )(H)2 . The dihydride complex undergoes Co‐H site exchange in solution and readily eliminates H2 . The Co I precursor (Cy‐PSiP)Co(PMe3 )N2 is a competent precatalyst for the hydrogenation of terminal alkenes. Exposure of (Cy‐PSiP)CoI to O2 gas under anhydrous conditions led to rapid ligand oxidation at Si and P, with no evidence observed at low temperature for a Co III superoxo or peroxo intermediate. Exclusive oxidation at Si to afford a Co II ‐siloxy complex was observed upon treatment of (Cy‐PSiP)CoI with one equiv. Me3 NO. While this siloxy complex did not react further with O2, treatment with a second equiv. of Me3 NO led to subsequent oxidation involving one phosphino donor. This observation supports the notion that in the ligand oxidation reactivity observed with O2, the O atoms incorporated at both Si and P are likely derived from the same O2 molecule. Abstract : Studies of bis(phosphanyl)silyl ligated cobalt complexes revealed examples of H2 oxidative addition via Co I and ligand oxidation via reactions of Co II species with O2 and Me3 NO.