Mononuclear and Binuclear Chromium (III) Picolinate Complexes

Diane M. Stearns, William H. Armstrong

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Abstract

The chromium(III) picolinate complexes [Cr(pic)3] (1) and [Cr(pic)2OH]2(2) (where pic = 2-carboxypyridine) have been isolated from the reaction of chromium(III) chloride and picolinic acid in aqueous solution. The monomeric complex 1-H2O (CrC18H14N3O7) crystallizes in the monoclinic space group C2/c with a = 30.219 (3) Å, b = 8.529 (1) Å, c = 13.942 (2) Å, β = 95.141 (1)°, V= 3579 (2) Å3, Z = 4, R = 0.032, and Rw= 0.043 for 1815 reflections (I > 3σ(I)). The binuclear complex 2.5H2O (Cr2C24H28N4O15) crystallizes in the monoclinic space group P21/n with a = 12.569 (2) Å, b = 18.839 (3) Å, c = 13.000 (4) Å, β = 105.823 (3)°, V= 2962 (2) Å3, Z = 8, R = 0.046, RW, = 0.067 for 3250 reflections (I > 3σ(I)). The mononuclear complex 1 is the meridional isomer, not the facial isomer as previously assumed. For 2 the bridging geometry is as follows: Cr-Cr = 2.999 (1) Å; Cr-O(bridge) range = 1.934 (3)-1.980 (3) Å; Cr-O-Cr = 99.0 (1), 101.6(1)°; O-Cr-O = 79.4 (1), 79.9 (1)°. Magnetic susceptibility data for 2 were measured from 280 to 6 K and can be fit using an isotropic spin-exchange Hamiltonian, Ή = -2JŜ1Ŝ2, with a weak antiferromagnetic interaction (J = -8.02 (4) cm-1), g = 1.844, and a 2.23 (4) mol % paramagnetic impurity. The extent of magnetic coupling in 2 is compared to predictions made by the Glerup-Hodgson-Pedersen (GHP) equation. Compounds 1 and 2 are discussed in the general context of biologically active chromium.

Original languageEnglish (US)
Pages (from-to)5178-5184
Number of pages7
JournalInorganic Chemistry
Volume31
Issue number25
DOIs
StatePublished - Dec 1 1992
Externally publishedYes

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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