A high field and frequency electron paramagnetic resonance study of the S=2 chromium(II) complex trans-[Cr(NCCH3)4(FBF3)2] and investigation of its reaction with dioxygen: Crystal structure of [(CH3CN)5CrOCr(NCCH3)5](BF4)4·2CH3CN

• DOI: 10.1016/j.ica.2011.02.024
• Publication Date: 2011-02-17T11:18:33Z
• Authors: Anne-Laure Barra; Anders Døssing; Thorbjørn Morsing; Johan Vibenholt
• Keywords: [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus]; [CHIM.COOR]Chemical Sciences/Coordination chemistry; [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph]; 540; 01 natural sciences; 0104 chemical sciences

Abstract From high field and frequency electron paramagnetic resonance (EPR) powder spectra of the high spin chromium(II) complex trans-[Cr(NCCH3)4(FBF3)2] (1) recorded at T = 5–40 K the EPR parameters were found to be D = −2.19 cm−1, E ≈ 0 cm−1, and g‖ = g⊥ = 1.9833. The reaction between a MeCN solution of 1 and dioxygen gave dark green crystals of [(CH3CN)5CrOCr(NCCH3)5](BF4)4·2CH3CN (2). From the X-ray crystal structure of 2 at T = 122 K a Cr–O–Cr angle of 180° and a Cr–O distance of 1.7556(5) A was found. This is the shortest among the known Cr–O distances in dinuclear complexes containing a CrOCr4+ core, and this can partly explain the strong antiferromagnetic coupling between the two chromium(III) centers in 2.