Half‐Sandwich Osmium(II) Complexes with Bidentate N, N‐Chelating Ligands and Their Use in the Transfer Hydrogenation of Ketones. Issue 5 (6th February 2017)

• Record Type: Journal Article
• Authors: Gichumbi, Joel M.; Omondi, Bernard; Friedrich, Holger B.
• Is Part Of: European journal of inorganic chemistry. Issue 5(2017)
• Page Start: 915
• Page End: 924
• Publication Date: 2017-02-06
• Subjects: Osmium -- Transfer hydrogenation -- N ligands -- Chelates -- Ketones; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201601249
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : The reaction of appropriate N, N‐bidentate ligands with the [(η 6 ‐p ‐cymene)Os(µ‐Cl)Cl]2 dimer ( p ‐cymene = C10 H14 ), followed by metathesis reaction with NH4 PF6, gave the new osmium(II) arene complex salts [(η 6 ‐p ‐cymene)OsCl(C5 H4 N‐2‐CH=N–R)]PF6, where [R = tert ‐butyl (1 ), isopropyl (2 ), 2, 6‐dimethylphenyl (3 ), or 2, 6‐diisopropylphenyl (4 )]. The dimer was also reacted with the N, N′‐bidentate ligands di‐(2‐pyridyl)amine (5 ), 4‐phenyl‐3, 6‐di(2‐pyridyl)pyridazine (6 ), 4, 4′‐di‐ tert ‐butyl‐2, 2′‐bipyridine (7 ), and 5, 5′‐dimethyl‐2, 2′‐bipyridine (8 ). In addition, the reaction of the precursor [(η 6 ‐C6 H6 )Os(µ‐Cl)Cl]2 with the N, N′‐bidentate ligands gave [(η 6 ‐C6 H6 )OsCl(N, N)]2 where N, N = 4, 4′‐di‐ tert ‐butyl‐2, 2′‐bipyridine (9 ), 5, 5′‐dimethyl‐2, 2′‐bipyridine (10 ), 3, 6‐bis(2‐pyridyl)‐4‐phenyl pyridazine (11 ), or di‐(2‐pyridyl)amine (12 ). The compounds were characterized by using 1 H and 13 C NMR, UV/Vis, FTIR spectroscopy and elemental analysis. The single‐crystal X‐ray structures for compounds1, 4, 8, 10, 11, and12 showed that the osmium(II) complexes adopted the classical three‐legged piano stool geometry. These osmium(II) compounds were found to be effective catalysts for the transfer hydrogenation of ketones into alcohols with NaOH as base and 2‐propanol as the solvent and hydrogen source. A range of cyclic, aromatic, and aliphatic ketones was studied and good turnover numbers achieved. Abstract : The synthesis of new [(η 6 ‐arene)OsCl(N, N)]PF6 complexes with bidentate ligands is reported. The single‐crystal X‐ray structures for five of these compounds showed the classical three‐legged piano stool geometry. The compounds were found to be effective catalysts for the transfer hydrogenation of ketones into alcohols with NaOH as base and 2‐propanol as the solvent and hydrogen source.