Search

Abstract: The meta-diaminoaryl ferrocenes Fc–NCN–H (3) and Fc–CNCN–H (5) (Fc=(η5-C5H5)(η5-C5H4)Fe, NCN–H=C6H3(CH2NMe2)2-3,5) can be used as precursors in the preparation of heterobimetallic transition metal complexes of structural type Fc–NCN–MX (NCN=[C6H2(CH2NMe2)2-2,6]−; MX=PdCl (7), PtCl (8), PtI (9)) and Fc–CNCN–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 SO2 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 C6H2 moiety is with 27.2(3)° and 38.2(3)° tilted towards the C5H4 entity, while in 13 an angle of 45.9(3)° can be found. The d8-electron configured platinum atoms possess a somewhat distorted square-planar surrounding, setup by two Me2NCH2 ortho-substituents, the NCN Cipso carbon atom and the chloride ligand. [Copyright &y& Elsevier]

Abstract: The synthesis and characterization of homobimetallic palladium and platinum complexes of type [(Me(O)CS-4-NCN–M←N∩N→M–NCN-4-SC(O)Me](OTf)2 (Me(O)CS-4-NCN=[C6H2(CH2NMe2)2-2,6-SC(O)Me-4]−; N∩N=4,4′-bipyridine (bipy); M=Pd, 12; M=Pt, 13) is reported. The required bifunctional thio-acetyl NCN pincer starting compound NC(Br)N-4-SC(O)Me (2) has been synthesized by the consecutive reactions of NC(Br)N–I (I-1-C6H2(CH2NMe2)2-3,5-Br-4) (1) with t BuLi, S8 and Me(O)CCl, respectively. Chemoselective metallation at the Caryl–Br bond was achieved by the reaction of 2 with the palladium(0) source [Pd2(dba)3] (3) (dba=dibenzylidene acetone). Treatment of thus formed [Pd(NCN-4-SC(O)Me)(Br)] (4) with [AgOTf] (8) (OTf=triflate, OSO2CF3) gave [Pd(NCN-4-SC(O)Me)(H2O)][OTf] (9) which was further reacted with 0.5equiv. of 4,4′-bipyridine (11a) to afford rigid-rod structured 12. When [Pt(tol)2(SEt2)]2 (5) (tol=4-tolyl) was used instead of 3, then 13 was produced via the in situ formation of [PtBr(NCN-4-SC(O)Me)] (7) and [Pt(NCN-4-SC(O)Me)(H2O)][OTf] (10). Another possibility to synthesize 7 relied upon the subsequent reaction of 1 with 0.5equiv. of 5 to give [PtBr(NCN-4-I)] (6) which further reacted with t BuLi, 1/8 S8 and Me(O)CCl to afford 7. The cyclic voltammograms of 2, 7, and 13 are discussed. Complex 7 was structurally characterized by single crystal X-ray crystallography. Organometallic 7 crystallizes with three independent molecules in the asymmetric unit and displays a monomeric structure as commonly encountered in d8-metal pincer chemistry. [Copyright &y& Elsevier]