Heterobimetallic Fe–Pd and Fe–Pt NCN pincer complexes (NCN = [C 6H 2(CH 2NMe 2) 2-2,6] −)

Abstract

The meta-diaminoaryl ferrocenes Fc–NCN–H ( 3) and Fc–C C–NCN–H ( 5) (Fc = (η 5-C 5H 5)(η 5-C 5H 4)Fe, NCN–H = C 6H 3(CH 2NMe 2) 2-3,5) can be used as precursors in the preparation of heterobimetallic transition metal complexes of structural type Fc–NCN–MX (NCN = [C 6H 2(CH 2NMe 2) 2-2,6] −; MX = PdCl ( 7), PtCl ( 8), PtI ( 9)) and Fc–C C–NCN–MX (MX = PdCl ( 11), PdI ( 12), PtCl ( 13)), respectively. They are accessible by applying different synthesis procedures, including oxidative addition and metallation– transmetallation processes. Cyclovoltammetric studies show that the ferrocene moieties in 3, 5, 7– 9 and 11- 13 can reversibly be oxidised. The potential of the Fe(II)/Fe(III) redox couple decreases with increasing electron density at the NCN pincer unit. The use of 8 as a possible (electro)chemical sensor in the detection of SO 2 is discussed as well. The solid-state structures of 8 and 13 are reported. The crystals of 8 contain two molecules of 8 in the asymmetric unit. The plane of the C 6H 2 moiety is with 27.2(3)° and 38.2(3)° tilted towards the C 5H 4 entity, while in 13 an angle of 45.9(3)° can be found. The d 8-electron configured platinum atoms possess a somewhat distorted square-planar surrounding, setup by two Me 2NCH 2 ortho-substituents, the NCN C ipso carbon atom and the chloride ligand.