Generation of a heterobimetallic FeMoS system containing intermediate spin [FeIIN4S2] functionality: Synthesis, characterisation and redox chemistry of [(N-N)2FeS2MoS2] (N-N=bipy or phen)

Tetrathiomolybdate reacts with iron (II) in the presence of bidentate ligands to form neutral binuclear complexes [Fe(N-N)^sub 2^MoS^sub 4^] [N-N=2-2'bipyridine(bipy) and 1,10-phenanthroline(phen)] showing intermediate spin character for Fe^sup II^. The spin state of the complexes has been examined by variable temperature magnetic moment (VTM) measurements and by variable temperature Mössbauer spectroscopy. The Mössbauer spectra indicate the presence of two iron sites: one of intermediate spin and the other of low spin at room temperature. The low spin site predominates over the intermediate spin as the temperature is lowered. The structural features of the complexes are supported by i.r., Raman, electronic and FAB mass spectra and by X-ray powder diffraction data. Substitution of one bipy/phen ligand in [Fe(N-N)^sub 3^]^sup 2+^ by MS^sub 4^^sup 2-^ ligands does not impart any major effect towards the size of the redox potentials of the tris-bipy/phen complexes, although the reversible nature of their cyclic voltammetric response is affected.[PUBLICATION ABSTRACT]