A series of thiophene tungsten Fischer carbene complexes of type [(CO)(5)W=C(OMe)R] (1, R = 2 Th; 4, R = fcthFc) and [(CO)(5)W=C(OMe)-R'-(OMe)C=W(CO)(5)] (2, R' = th; 5, R' = fcthfc) was synthesized for investigating low energy charge transfer interactions between the carbene substituents and the transition metal carbonyl fragment incorporating the thiophene heterocyclic system (Th = Thienyl; th = 2,5-thiendiyl; Fc = ferrocenyl; fc = 1,1'-ferrocenediyl). Electrochemical investigations were carried out on these complexes to get a closer insight into the electronic properties of 1, 2, 4 and 5. Typical electrode reactions could be found for the carbene reductions itself and for the tungsten carbonyl oxidation processes in all metal carbene complexes. However, for the thiophene complex 2 two well-separated one-electron reduction events were observed, suggesting an interaction of the Fischer carbene moieties in 2(-), over the thiophene bridge. Reversible one-electron redox events for the ferrocenyl moieties in complexes 4 and 5 were also observed. During the UV Vis NIR spectroelectrochemical investigations typical low energy absorptions for the mixed-valent alpha,alpha'-diferrocenyl thiophene increment were found for these two complexes, as well as high energy NIR absorptions, which were attributed to metal metal charge transfer transition between the tungsten carbonyl increment and the ferrocenyl units (complexes 4 and 5). Further infrared spectroelectrochemical studies reveal that the electronic interactions between the tungsten carbene and the ferrocenyl electrophores in the corresponding cationic species (4(+), 4(2+), 5(+), 5(2+)) can be described with weakly coupled class II systems according to Robin and Day. (c) 2014 Elsevier BY. All rights reserved.