Linear Tricobalt Compounds with Di(2-pyridyl)amide (dpa) Ligands: Temperature Dependence of the Structural and Magnetic Properties of Symmetrical and Unsymmetrical Forms of Co3(dpa)4Cl2 in the Solid State

• DOI: 10.1021/ja000515q
• Publication Date: 2002-07-26T05:57:48Z
• Authors: Rodolphe Clérac; F. Albert Cotton; Lee M. Daniels; Kim R. Dunbar; Kristin Kirschbaum; Carlos A. Murillo; A. Alan Pinkerton; Arthur J. Schultz; Xiaoping Wang
• Keywords: Orthorhombic crystal system; Monoclinic crystal system; Tetragonal crystal system; Amide

The linear trinuclear compound Co3(dpa)4Cl2 (1; dpa = di(2-pyridyl)amide anion) crystallizes from CH2Cl2 solution in two forms simultaneously, namely, an orthorhombic form 1·CH2Cl2 and a tetragonal 1·2CH2Cl2. three linearly arranged cobalt atoms 1 are supported by four ligands spiral configuration. chain of is symmetrical 1·CH2Cl2, but unsymmetrical Both crystal structures have been studied at various temperatures. A reversible second-order phase transition (165 K) (Pnn2) to monoclinic (Pn) symmetry for the has documented X-ray studies 296, 168, 109 K as well neutron diffraction study 20 K. tricobalt unit becomes slightly low temperature although Co−Co bonds remain statistically equivalent (Co−Co ≈ 2.32 Å) throughout experimental range. No was observed 1·2CH2Cl2 temperature, distances changed 2.299(1) 2.471(1) Å 298 2.3035(7) 2.3847(8) Magnetic susceptibility measurements indicate that compounds S 1/2 ground state exhibit gradual spin-crossover higher temperature.