Access to Heteroleptic Fluorido‐Cyanido Complexes with a Large Magnetic Anisotropy via Fluoride Abstraction

Silicon-mediated fluoride abstraction is demonstrated as a means of generating the first fluorido-cyanido transition metal complexes. This new synthetic approach is exemplified by the synthesis and characterization of the heteroleptic complexes, trans-[M IV F 4 (CN) 2 ] 2- (M = Re, Os), obtained from their homoleptic [M IV F 6 ] 2- parents. As shown by combined high-field electron paramagnetic resonance spectroscopy and magnetization measurements, the partial substitution of fluoride by cyanide ligands leads to a dramatic increase in the magnetic anisotropy of trans-[ReF 4 (CN) 2 ] 2- as compared to [ReF 6 ] 2- , reflecting the severe departure from an ideal octahedral (O h point group) ligand field. This methodology paves the way toward the realization of new heteroleptic transition metal complexes that may be used as highly anisotropic building-blocks for the design of high-performance molecule-based magnetic materials.