The chemistry of vitamin B12. Part 22. Steric effects in the co-ordination of amines by cobalt(III) corrinoids

David A. Baldwin; Eric A. Betterton; John M. Pratt

doi:10.1039/DT9830002217

The chemistry of vitamin B₁₂. Part 22. Steric effects in the co-ordination of amines by cobalt(III) corrinoids

David A. Baldwin
, Eric A. Betterton
, John M. Pratt

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

Abstract

The following equilibrium constants (given as log₁₀K/dm³ mol^-1) have been determined by spectrophotometry for the substitution in cobalt(III) corrinoids of co-ordinated H₂O by various amines B with different trans ligands X in aqueous solution (I = 0.2 mol dm^-3) at 25 °C: X = 5,6-dimethylbenzimidazole (dbzm), B = NH₂Me (ca. 6), NHMe₂ (3.4), NMe₃ (≤1), NH₂Et (5.3), NH₂Prⁱ and NH₂Bu^t (both ≤1); X = CN^-, B = NH₂Me (3.4), NHMe₂(2.0), NMe₃(ca. 0); X = vinyl, B = NH₃ (-0.06), NH₂Me (+0.04), NHMe₂ and NMe₃ (both ≤ - 1). These results show that steric effects increase in importance as the donor power of the trans ligand X decreases (from vinyl through CN^- to dbzm) and that significant steric effects are caused by substitution on the β (C) atom as well as on the α (N) atom.

Original language	English (US)
Pages (from-to)	2217-2222
Number of pages	6
Journal	Journal of the Chemical Society, Dalton Transactions
Issue number	10
DOIs	https://doi.org/10.1039/DT9830002217
State	Published - 1983

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General Chemistry

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title = "The chemistry of vitamin B12. Part 22. Steric effects in the co-ordination of amines by cobalt(III) corrinoids",

abstract = "The following equilibrium constants (given as log10K/dm3 mol-1) have been determined by spectrophotometry for the substitution in cobalt(III) corrinoids of co-ordinated H2O by various amines B with different trans ligands X in aqueous solution (I = 0.2 mol dm-3) at 25 °C: X = 5,6-dimethylbenzimidazole (dbzm), B = NH2Me (ca. 6), NHMe2 (3.4), NMe3 (≤1), NH2Et (5.3), NH2Pri and NH2But (both ≤1); X = CN-, B = NH2Me (3.4), NHMe2(2.0), NMe3(ca. 0); X = vinyl, B = NH3 (-0.06), NH2Me (+0.04), NHMe2 and NMe3 (both ≤ - 1). These results show that steric effects increase in importance as the donor power of the trans ligand X decreases (from vinyl through CN- to dbzm) and that significant steric effects are caused by substitution on the β (C) atom as well as on the α (N) atom.",

author = "Baldwin, \{David A.\} and Betterton, \{Eric A.\} and Pratt, \{John M.\}",

year = "1983",

doi = "10.1039/DT9830002217",

language = "English (US)",

pages = "2217--2222",

journal = "Journal of the Chemical Society, Dalton Transactions",

issn = "1472-7773",

publisher = "Royal Society of Chemistry",

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T1 - The chemistry of vitamin B12. Part 22. Steric effects in the co-ordination of amines by cobalt(III) corrinoids

AU - Baldwin, David A.

AU - Betterton, Eric A.

AU - Pratt, John M.

PY - 1983

Y1 - 1983

N2 - The following equilibrium constants (given as log10K/dm3 mol-1) have been determined by spectrophotometry for the substitution in cobalt(III) corrinoids of co-ordinated H2O by various amines B with different trans ligands X in aqueous solution (I = 0.2 mol dm-3) at 25 °C: X = 5,6-dimethylbenzimidazole (dbzm), B = NH2Me (ca. 6), NHMe2 (3.4), NMe3 (≤1), NH2Et (5.3), NH2Pri and NH2But (both ≤1); X = CN-, B = NH2Me (3.4), NHMe2(2.0), NMe3(ca. 0); X = vinyl, B = NH3 (-0.06), NH2Me (+0.04), NHMe2 and NMe3 (both ≤ - 1). These results show that steric effects increase in importance as the donor power of the trans ligand X decreases (from vinyl through CN- to dbzm) and that significant steric effects are caused by substitution on the β (C) atom as well as on the α (N) atom.

AB - The following equilibrium constants (given as log10K/dm3 mol-1) have been determined by spectrophotometry for the substitution in cobalt(III) corrinoids of co-ordinated H2O by various amines B with different trans ligands X in aqueous solution (I = 0.2 mol dm-3) at 25 °C: X = 5,6-dimethylbenzimidazole (dbzm), B = NH2Me (ca. 6), NHMe2 (3.4), NMe3 (≤1), NH2Et (5.3), NH2Pri and NH2But (both ≤1); X = CN-, B = NH2Me (3.4), NHMe2(2.0), NMe3(ca. 0); X = vinyl, B = NH3 (-0.06), NH2Me (+0.04), NHMe2 and NMe3 (both ≤ - 1). These results show that steric effects increase in importance as the donor power of the trans ligand X decreases (from vinyl through CN- to dbzm) and that significant steric effects are caused by substitution on the β (C) atom as well as on the α (N) atom.

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DO - 10.1039/DT9830002217

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SP - 2217

EP - 2222

JO - Journal of the Chemical Society, Dalton Transactions

JF - Journal of the Chemical Society, Dalton Transactions

IS - 10

ER -

The chemistry of vitamin B₁₂. Part 22. Steric effects in the co-ordination of amines by cobalt(III) corrinoids

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