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Supramolecular Macrocyclic Pd(II) and Pt(II) Squares and Rectangles with Aryldithiolate Ligands and their Excellent Catalytic Activity in Suzuki C–C Coupling Reaction

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posted on 02.11.2015, 00:00 by K. V. Vivekananda, S. Dey, D. K. Maity, N. Bhuvanesh, V. K. Jain
Addition of 1,4-benezenedithiol and 4,4′-biphenyldithiol to M­(OTf)2 (M = cis-[Pt­(PEt3)2]2+ or cis-[Pd­(dppe)]2+) (dppe = 1,2-bis­(diphenylphosphino)­ethane) gave self-assembled tetranuclear complexes [M2{S­(C6H4)nS}]2­(OTf)4 (n = 1, 2). The same reaction with 1,4-benezenedimethanethiol yielded octanuclear supramolecular coordination complexes (SCC) [M2{SCH2C6H4CH2S}]4­(OTf)8. These complexes were characterized by NMR, mass, and UV–vis spectroscopies, cyclic voltammetry, as well as density functional theory studies and represent the first examples of SCCs constructed by thiolate groups and square-planar metal ions. The rectangular shape of tetranuclear complexes and square shape of octanuclear complex are confirmed by single-crystal structures and computational studies. The palladium complexes showed excellent catalytic activity in Suzuki C–C cross-coupling reactions with high turnover numbers (2 × 107), even with low catalyst loading.