title: Stereoselective Alkane Oxidation with meta-Chloroperoxybenzoic Acid (MCPBA) Catalyzed by Organometallic Cobalt Complexes.
abstract: Cobalt pi-complexes, previously described in the literature and specially synthesized and characterized in this work, were used as catalysts in homogeneous oxidation of organic compounds with peroxides. These complexes contain pi-butadienyl and pi-cyclopentadienyl ligands: [(tetramethylcyclobutadiene)(benzene)cobalt] hexafluorophosphate, [(C₄Me₄)Co(C₆H₆)]PF₆ (1); diiodo(carbonyl)(pentamethylcyclopentadienyl)cobalt, Cp*Co(CO)I₂ (2); diiodo(carbonyl)(cyclopentadienyl)cobalt, CpCo(CO)I₂ (3); (tetramethylcyclobutadiene)(dicarbonyl)(iodo)cobalt, (C₄Me₄)Co(CO)₂I (4); [(tetramethylcyclobutadiene)(acetonitrile)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [(C₄Me₄)Co(bipy)(MeCN)]PF₆ (5); bis[dicarbonyl(B-cyclohexylborole)]cobalt, [(C₄H₄BCy)Co(CO)₂]₂ (6); [(pentamethylcyclopentadienyl)(iodo)(1,10-phenanthroline)cobalt] hexafluorophosphate, [Cp*Co(phen)I]PF₆ (7); diiodo(cyclopentadienyl)cobalt, [CpCoI₂]₂ (8); [(cyclopentadienyl)(iodo)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [CpCo(bipy)I]PF₆ (9); and [(pentamethylcyclopentadienyl)(iodo)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [Cp*Co(bipy)I]PF₆ (10). Complexes1and2catalyze very efficient and stereoselective oxygenation of tertiary C-H bonds in isomeric dimethylcyclohexanes with MCBA: cyclohexanols are produced in 39 and 53% yields and with thetrans/cisratio (of isomers with mutualtrans- orcis-configuration of two methyl groups) 0.05 and 0.06, respectively. Addition of nitric acid as co-catalyst dramatically enhances both the yield of oxygenates and stereoselectivity parameter. In contrast to compounds1and2, complexes9and10turned out to be very poor catalysts (the yields of oxygenates in the reaction withcis-1,2-dimethylcyclohexane were only 5%-7% andtrans/cisratio 0.8 indicated that the oxidation is not stereoselective). The chromatograms of the reaction mixture obtained before and after reduction with PPh₃ are very similar, which testifies that alkyl hydroperoxides are not formed in this oxidation. It can be thus concluded that the interaction of the alkanes with MCPBA occurs without the formation of free radicals. The complexes catalyze oxidation of alcohols withtert-butylhydroperoxide (TBHP). For example,tert-BuOOH efficiently oxidizes 1-phenylethanol to acetophenone in 98% yield if compound1is used as a catalyst.
authors.affiliation: Semenov Institute of Chemical Physics, Russian Academy of Sciences, ulitsa Kosygina, dom 4, Moscow 119991, Russia. shulpin@chph.ras.ru.|Chair of Chemistry and Physics, Plekhanov Russian University of Economics, Stremyannyi pereulok, dom 36, Moscow 117997, Russia. shulpin@chph.ras.ru.
authors.forename: Georgiy B
authors.initials: GB
authors.lastname: Shul'pin
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. dloginov@ineos.ac.ru.
authors.forename: Dmitriy A
authors.initials: DA
authors.lastname: Loginov
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. shulpina@ineos.ac.ru.
authors.forename: Lidia S
authors.initials: LS
authors.lastname: Shul'pina
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. ikonns@ineos.ac.ru.
authors.forename: Nikolay S
authors.initials: NS
authors.lastname: Ikonnikov
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. vladchem32@gmail.com.
authors.forename: Vladislav O
authors.initials: VO
authors.lastname: Idrisov
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. mmvngrdv@gmail.com.
authors.forename: Mikhail M
authors.initials: MM
authors.lastname: Vinogradov
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. osipov@ineos.ac.ru.
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Osipov
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsaVavilova, dom 28, Moscow 119991, Russia. unelya@xrlab.ineos.ac.ru.
authors.forename: Yulia V
authors.initials: YV
authors.lastname: Nelyubina
authors.affiliation: Chair of Chemistry and Physics, Plekhanov Russian University of Economics, Stremyannyi pereulok, dom 36, Moscow 117997, Russia. popov.AnA@rea.ru.
authors.forename: Polina M
authors.initials: PM
authors.lastname: Tyubaeva
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D002384:Catalysis; D002723:Chlorobenzoates / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D000473:Alkanes; D002723:Chlorobenzoates; D009942:Organometallic Compounds; D003035:Cobalt; C000433:3-chloroperbenzoic acid
keywords: X-ray analysis; alcohols; alkanes; meta-chloroperoxybenzoic acid (MCPBA); metal complexes; stereoselective oxidation