Complexes with the formula [M(diimine)(CN-BR3)(4)](2-), where diimine = bipyridine (bpy), phenanthroline (phen), 3,5-trifluoromethylbipyridine (flpy), R = Ph, C6F5, and M = Fe-II, Ru-II, were synthesized and characterized by X-ray crystal structure analysis, UV-visible spectroscopy, IR spectroscopy, and voltammetry. Three highly soluble complexes, [Fe-II(bpy)(CN-B(C6F5)(3))(4)](2-), [Ru-II(bpy)(CN-B-(C6F5)(3))(4)](2-), and [Ru-II(flpy)(CN-B(C6F5)(3))(4)](2-), exhibit electrochemically reversible redox reactions, with large potential differences between the bpy(0/)- or flpy(0/-) and M-III/II couples of 3.27, 3.52, and 3.19 V, respectively. CASSCF+NEVPT2 calculations accurately reproduce the effects of borane coordination on the electronic structures and spectra of cyanometallates.