Five-Coordinated Bis-o-semiquinonato Cobalt(II) Complex with Triarylphosphine.

Bis-3,6-di-tert-butyl-o-benzosemiquinonato cobalt complex with tris(2,6-dimethoxyphenyl)phosphine was synthesized and characterized. Single crystal X-ray diffraction studies indicate a highly distorted square-pyramidal coordination environment of cobalt. Phosphorus atom lies in the base of pyramid. Coordination geometry essentially changes with cooling. Magnetic measurements and DFT calculations indicate quartet ground state at both temperatures (100 and 298 K). Quantum-chemical study has showed that significant variation of exchange interaction energies between spins of paramagnetic centers occurs with lowering temperature. [ABSTRACT FROM AUTHOR]