Mononuclear Four-Coordinate Bis-Fluoride Bis-NHC Complexes of Chromium(II), Iron(II), and Cobalt(II)

• Published in: Inorganic chemistry 2023-11, Vol.62 (44), p.18108-18115
• Main Authors: Acosta, Carlos M., Belov, Dmitry S., Lamur, Andy H., Brantley, ChristiAnna L., Solans-Monfort, Xavier, Rue, Kelly L., Christou, George, Bukhryakov, Konstantin V.
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c02442

The reaction between silylamido complexes of Cr­(II), Fe­(II), and Co­(II) and IMes·2HF salt in the presence of IMes (IMes = 1,3-dimesitylimidazol-2-ylidene) led to isolation of Cr­(IMes)2F2 (2-Cr), Fe­(IMes)2F2 (2-Fe), and Co­(IMes)2F2 (2-Co). X-ray structural studies revealed that 2-Cr adopts square planar geometry, while 2-Fe and 2-Co have distorted tetrahedral geometry. Magnetic susceptibility studies of 2-Cr, 2-Fe, and 2-Co were consistent with high-spin complexes, S = 2 for 2-Cr/2-Fe and S = 3/2 for 2-Co. We demonstrated that fluoride can be successfully exchanged for cyanide and azide using trimethylsilyl cyanide and trimethylsilyl azide (3-Fe and 4-Fe). DFT studies suggest that the preference of 2-Cr to adopt square planar geometry over tetrahedral is due to its d4 metal center, where four electrons fill the lower-lying d-orbitals.