Biferrocene NCN pincer metal-d8 complexes:: Synthesis, reaction chemistry and cyclovoltammetric studies

The synthesis of biferrocene-bridged NCN pincer palladium and platinum complexes (NCN = [1-C6H2(CH2NMe2)(2)-3,5](-)) is discussed. Sonogashira cross-coupling of [(eta(5)-C5H4)Fe(eta(5)-C5H4C CH)](2) (1) with I-1-NCN-4-X (2a, X = H; 26 X = Br) produces [(eta(5)-C5H4)Fe(eta(5)-C5H4C C-1-NCN-4-X)](2) (3a, X = H; 3b, X = Br). Homobimetallic 3b further reacts with [Pd-2(dba)(3) . CHCl3] (4) or [Pt(tol)(2)(SEt2)](2) (5) (dba = dibenzylidene acetone, tol = 4-tolyl), respectively, to give tetrametallic [(eta(5)-C5H4)Fe(eta(5)-C5H4C C-4-NCN-1-MBr)](2) (6, M = Pd; 7, M = Pt) in which NCN-MBr fragments are connected by a biferrocene unit. Cyclovoltammetric studies show that the ferrocene moieties can independently be oxidized. The difference of the Fe(II)/Fe(III) redox couples amounts to ca. 300 mV and is not affected by the nature of the NCN pincer metal moities. (c) 2006 Elsevier B.V. All rights reserved.