Pentacyanido(L)ferrate(III) complexes: Crystal structures, electrochemical and DFT studies (L = pyrazine, 4,4′-bipyridine, azide)

Abstract The crystal structures of two pentacyanido(L) ferrate(III) complexes, [P(C 6 H 5 ) 4 ] 2 [Fe(CN) 5 (prz)]·4H 2 O 1 , [P(C 6 H 5 ) 4 ] 2 [Fe(CN) 5 (4,4′-bipy)]·3H 2 O 2 , have been solved. Within the two complex anions the iron atoms are hexacoordinated by five cyanido ligands, the sixth position being occupied by the nitrogen atom arising from pyrazine and, respectively, 4,4′-bipyridine. The electrochemical properties of compounds 1 , 2 and of the azido derivative, (Ph 4 As) 2 [Na(H 2 O) 4 ][Fe(CN) 5 (N 3 )] 3 , have been investigated by cyclic voltammetry. A relatively complicated redox behavior of these complexes was found, due especially to the electron transfer involving the central metallic ion that changes reversibly its oxidation state (Fe III /Fe II redox site) and also to the coligand (4,4′-bipyridine, pyrazine or azide) which intervenes in a distinct electron transfer. The experimental data have been rationalized through DFT calculations.