Inner-Sphere Electron-Transfer Stereoselectivities in the Oxidation of Bis(1,2-diaminoethane)cobalt(II) Derivatives by [Co(ox)3]3−

Rosemary A. Marusak, Marie A. Ivanca, Kenneth J. Haller, A. Graham Lappin

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Abstract

[Co(N,N-Me2en)2(ox)]+ (N,N-Me2en = N.N-dimethyl-1,2-diaminoethane, ox2- = oxalate(2−)) is the sole product in the innersphere reduction of [Co(ox)3]3− by cobalt(II) in solutions of N,N-Me2en and is formed stereoselectively with an enantiomeric excess of 4.3% ΔΛ. The structure of this product has been determined by X-ray crystallography. [Δ-Co(N,N-Me2en)2(ox)]I crystallizes in the orthorhombic space group Pbca (No. 61) with Z = 8, a = 15.206 (2) Å, b = 12.523 (2) Å, c = 16.999 (2) Å, and R = 0.039 for 2681 reflections. Four inner-sphere products are isolated in the corresponding reaction with N,N′-Me2en (N,N′-Me2en = N,N′-dimethyl-1,2-diaminoethane). The structure of the major product [Λ(RS,KS)/Δ(SR,SR)-Co(NN′-Me2en)2(ox)]+ (40%) has been determined by X-ray crystallography. [Δ(SR,SR)-Co(N,N′-Me2en)2(ox)]I•2H2O crystallizes in the monoclinic space group P21 (No. 4) with Z = 2, a = 8.260 (2) Å, b = 7.735 (1) Å, c = 13.697 (3) A, β = 101.96 (1)°, and R = 0.088 for 2434 reflections. Two isomers Λ(RR,SS)/Δ(RR,SS) (24%) and Λ(SS,RS)/Δ(RR,SR) (22%) are also formed as products. Stereoselectivities are 7.8% ΔΔ, 8.1% ΔΔ, and 7.7% ΔΔ, respectively. The fourth, minor product is also formed stereoselectively but is not unambiguously characterized. Stereoselectivities reflect hydrogen bonding in outer-sphere intermediates in the formation of the inner-sphere precursor complexes.

Original languageEnglish (US)
Pages (from-to)618-623
Number of pages6
JournalInorganic chemistry
Volume30
Issue number4
DOIs
StatePublished - Feb 1 1991
Externally publishedYes

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