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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Abstract
Addition of 1,4-benezenedithiol and
4,4′-biphenyldithiol to M(OTf)<sub>2</sub> (M = <i>cis</i>-[Pt(PEt<sub>3</sub>)<sub>2</sub>]<sup>2+</sup> or <i>cis</i>-[Pd(dppe)]<sup>2+</sup>) (dppe = 1,2-bis(diphenylphosphino)ethane)
gave self-assembled tetranuclear complexes [M<sub>2</sub>{S(C<sub>6</sub>H<sub>4</sub>)<sub><i>n</i></sub>S}]<sub>2</sub>(OTf)<sub>4</sub> (<i>n</i> = 1, 2). The same reaction
with 1,4-benezenedimethanethiol yielded octanuclear supramolecular
coordination complexes (SCC) [M<sub>2</sub>{SCH<sub>2</sub>C<sub>6</sub>H<sub>4</sub>CH<sub>2</sub>S}]<sub>4</sub>(OTf)<sub>8</sub>. 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 ×
10<sup>7</sup>), even with low catalyst loading
