The neutral dppfFe(NO)(2) (1), the novel cationic [dppfCo(NO)(2)][SbF6] (2), as well as the dppfFe(CO)(3) (3) (dppf = 1,1'-bis(diphenylphosphino)ferrocene) complexes were prepared and characterized. The interaction between the two metallic centers through the dppf ligand was studied in the solid state by Fe-57 Mossbauer spectroscopy and in solution by cyclic voltammetry. The Mossbauer parameters are compared with those of other dppfML(n) complexes. Electrochemical studies performed on these complexes show the great influence of the MLn moiety on the redox processes of the dppf iron center. The crystal structure of complex 2 was determined (C34H28CoF6FeN2O2P2Sb). The compound crystallizes in the triclinic, space group <P(1)over bar>, a = 10.441 (2), b = 10.755(2), c = 17.320(5) Angstrom, alpha = 104.10(2), beta = 0.504(10), gamma = 111.504(10)degrees, U = 1744.7(7) Angstrom(3), Z = 2, R = 0.0765, wR2 = 0.1878. In this complex, the cobalt atom is coordinated to two nitrosyl ligands and to phosphorus atoms of the dppf ligand, providing a distorted tetrahedral geometry. (C) 1997 Elsevier Science S.A.26611927