Propyltrimethoxysilane-thiolate iron and nickel complexes: Synthesis, characterization and electrochemical behaviour

Abstract

The new thiolate-bridged nickel dimer [Ni(η-C 5H 5){μ-S(CH 2) 3(OMe) 3}] 2 ( 1), has been obtained by reaction of 3-mercaptopropyltrimethoxysilane with nickelocene. Thermal reaction between [Fe(CO) 2(η-C 5H 5)] 2 and the disulphide [S(CH 2) 3Si(OMe) 3] 2 in cyclohexane gives the dinuclear thiolate- bridged complex [Fe(CO)(η-C 5H 5){μ-S(CH 2) 3Si(OMe) 3}] 2 ( 2), which can be isolated as two isomeric forms. Oxidation of 2 can be achieved by treatment with ferricinium hexafluorophosphate, resulting in the paramagnetic monocationic dinuclear species [Fe(CO)(η-C 5H 5){μ-S(CH 2) 3Si(OMe) 3}] 2PF 6 ( 3). Reaction of [Fe(CO) 2(η-C 5R 5)Br] (R = H or Me) with HS(CH 2) 3Si(OMe) 3 in the presence of Et 3N, or with NaS(CH 2) 3Si(OMe) 3, in THF solution affords the mononuclear thiolate derivatives [Fe(CO) 2(ηC 5R 5){S(CH 2) 3Si(OMe) 3}] (R = H ( 4) or Me ( 5)). The electrochemical behaviour of the synthesized complexes has been studied using cyclic voltammetry and coulometry. The dinuclear species 1 and 2 have been oxidized voltammetrically and monocationic 1 + and 2 + and dicationic 1 2+ and 2 2+ species have been detected, 1 + and 2 + being characterized by ESR spectroscopy. The electrochemical oxidation of the mononuclear complexes 4 and 5 is followed by the elimination of [S(CH 2) 3Si(OMe) 3], the cationic species [Fe(CO) 2(η-C 5R 5)(THF)] + or [Fe(CO) 2(η-C 5H 5)PPh 3)] + being detected if the oxidation is carried out in the presence of PPh 3.