Dealkylation of alkylcobalt complexes by the mercury(II) electrophile

Magnuson, Virgil E.; Weber, James H.

doi:10.1016/s0022-328x(00)83770-5

Cited by 22 publications

(7 citation statements)

References 11 publications

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“…The types of alkylcobalt(III) complexes investigated include cobalamins, cobamides, cobaloximes, and various tetradentate chelates with nitrogen or nitrogen and oxygen donor ligands. The studies have demonstrated alkyl transfer from cobalt complexes to chromium, [12][13][14][15][16] cobalt, 17-32 gold, 33 mercury, 23,[33][34][35][36][37][38][39][40][41] nickel, 42 palladium, 43 (1) DiMarco, A. A.; Bobik, T. A.; Wolfe, R. S. Annu.…”

Section: Introductionmentioning

confidence: 99%

Alkyl Exchange Reactions of Organocobalt Porphyrins. A Bimolecular Homolytic Substitution Reaction

Stolzenberg

Cao

2001

J. Am. Chem. Soc.

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Reaction of organocobalt(III) porphyrins with a cobalt(II) complex of a distinguishable porphyrin or tetrapyrrole resulted in the reversible exchange of the organic axial ligand. The exchange reaction was facile in such solvents as benzene, toluene, dichloromethane, chloroform, and pyridine; was unaffected by total exclusion of light; was faster than would be expected for a homolytic process given known Co-C bond dissociation energies; and was of broad scope with respect to the organic ligand. Methyl, benzyl, primary alkyl, secondary alkyl, and acyl groups exchanged, but phenyl groups did not. The position of the exchange equilibrium was independent of the direction of approach and was nonstatistical. The relaxation to equilibrium appeared to be consistent with that of a second-order process. The rate of the reaction varied with the identity of the R group in the order Bzl > or = Me > Et approximately n-Pr > i-Pr > i-Bu > acetyl approximately neopentyl approximately 2-adamantyl. However, the total variation in reaction rates was remarkably small. Attempts to find evidence of free-radical intermediates by trapping with TEMPO or CO or by alkyl group interchange with an excess of an alkyl halide of a distinct alkyl group were unsuccessful over a time scale comparable to multiple half-lives of the exchange reaction. In addition, no rearrangement products were detected in exchange reactions of the 5-hexenyl group. Use of cobalt porphyrin reactants that were sterically encumbered on both faces with groups large enough to prevent formation of a bridged, Co-C-Co structure resulted in a 5 or more order of magnitude decrease in the rate of methyl exchange, if not its outright cessation, when run with total exclusion of light. The decrease in the rate of the thermal exchange process revealed the existence a slow photochemical exchange process that was driven by room lights. All evidence was consistent with a bimolecular S(H)2 mechanism for the thermal exchange mechanism.

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Section: Introductionmentioning

confidence: 99%

Alkyl Exchange Reactions of Organocobalt Porphyrins. A Bimolecular Homolytic Substitution Reaction

Stolzenberg

Cao

2001

J. Am. Chem. Soc.

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“…The presence of the O•••H•••O bridging moieties in cobaloxime derivatives ensures co-planarity of the two molecules of ligand and promotes the stability of the cobaloxime molecule (Zangrando et al, 2003). The existence of O•••H•••O bridging is supported by NMR data and further substantiated by their chemical behavior with BF 3 .Et 2 O in readily forming an O-BF 2 -O system by deprotonation of an O•••H•••O bridge(Magnuson & Weber, 1974;Bakac & Espenson, 1984). The other O•••H•••O (O1•••H1•••O3) group is less bridging than the O2•••H2•••O4 group since H1 is substantially close to O3 than to O1 (O3-H1 = 1.03 (3) Å)…”

mentioning

confidence: 68%

“…For NMR research on OÁ Á ÁHÁ Á ÁO bridges, see: Bakac & Espenson (1984). For deprotonation of OÁ Á ÁHÁ Á ÁO bridges by BF 3 ÁEt 2 O, see: Magnuson & Weber (1974).…”

Section: Related Literaturementioning

confidence: 99%

Chloridobis(dimethylglyoximato-κ²N,N′)(ethyl pyridine-3-carboxylate-κN)cobalt(III)

Wang¹,

Sun²,

Wan³

et al. 2011

Acta Cryst E

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In the title compound, [Co(C4H7N2O2)2Cl(C8H9NO2)], which was prepared as a model complex of vitamin B12, the CoIII atom, which is linked to four N atoms of the pseudo-macrocyclic (dmgH)2 ligand (dmgH is dimethylglyoximate) in the equatorial plane and one Cl− anion and one N atom of ethyl nicotinate in apical positions, displays an approximately octahedral coordination. The Co atom is 0.0187 (8) Å out of the mean plane of the four equatorial N atoms. The structure has an O⋯H⋯O bridge, which is very common in cobaloxime derivatives, with O⋯H distances of 1.24 (2) and 1.25 (2) Å.

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“…The mean Co-N bond length is 1.898 Å (3). The (Bakac & Espenson, 1984;Magnuson & Weber, 1974). The distance between O2 and H2 is 1.14 (6) Å indicating a strongly hydrogen bonded nearly symmetric O-H•••O system (Bhuyan et al, 2007;Dutta et al, 2009;Mandal & Gupta, 2005, 2007.…”

Section: Data Collectionmentioning

confidence: 99%

“…For NMR research on O-HÁ Á ÁO bridges, see: Bakac & Espenson (1984). For deprotonation of O-HÁ Á ÁO bridges by BF 3 ÁEt 2 O, see: Magnuson & Weber (1974).…”

Section: Related Literaturementioning

confidence: 99%

Chloridobis(dimethylglyoximato-κ²N,N′)(ethyl pyridine-4-carboxylate-κN)cobalt(III) chloroform monosolvate

et al. 2012

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The title compound, [Co(C4H7N2O2)2Cl(C8H9NO2)]·CHCl3, was synthesized as a model complex of vitamin B12. The CoIII cation displays an approximately octahedral coordination environment, being displaced by 0.0240 (15) Å from the mean plane of the four N atoms of the equatorial plane. The O—H distances in the dimethylglyoximate hydroxy groups are 0.89 (6) and 1.14 (6) Å; such long O—H bonds are very common in cobaloxime derivatives. Weak classical O—H⋯N and non-classical C—H⋯Cl hydrogen-bonding interactions further consolidate the crystal packing.

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Dealkylation of alkylcobalt complexes by the mercury(II) electrophile

Cited by 22 publications

References 11 publications

Alkyl Exchange Reactions of Organocobalt Porphyrins. A Bimolecular Homolytic Substitution Reaction

Alkyl Exchange Reactions of Organocobalt Porphyrins. A Bimolecular Homolytic Substitution Reaction

Chloridobis(dimethylglyoximato-κ²N,N′)(ethyl pyridine-3-carboxylate-κN)cobalt(III)

Chloridobis(dimethylglyoximato-κ²N,N′)(ethyl pyridine-4-carboxylate-κN)cobalt(III) chloroform monosolvate

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Dealkylation of alkylcobalt complexes by the mercury(II) electrophile

Cited by 22 publications

References 11 publications

Alkyl Exchange Reactions of Organocobalt Porphyrins. A Bimolecular Homolytic Substitution Reaction

Alkyl Exchange Reactions of Organocobalt Porphyrins. A Bimolecular Homolytic Substitution Reaction

Chloridobis(dimethylglyoximato-κ2N,N′)(ethyl pyridine-3-carboxylate-κN)cobalt(III)

Chloridobis(dimethylglyoximato-κ2N,N′)(ethyl pyridine-4-carboxylate-κN)cobalt(III) chloroform monosolvate

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Chloridobis(dimethylglyoximato-κ²N,N′)(ethyl pyridine-3-carboxylate-κN)cobalt(III)

Chloridobis(dimethylglyoximato-κ²N,N′)(ethyl pyridine-4-carboxylate-κN)cobalt(III) chloroform monosolvate