Palladated Oligophenylene Thioethers: Synthesis and Reactivity toward Isocyanides, Carbon Monoxide, and Alkynes

Phenylene thioethers XC6H4(SC6H4R-4)-a (a = 2, 4; X = Br, I; R = H, OMe, NO2) react with Pd(dba)2 and 2 equiv of PPh3 or 1 equiv of 2,2′-bipyridine (bpy) to afford trans-[PdBr{C6H4(SC6H4R-4)-a}(PPh3)2] (for example, a = 2, R = H (1)) or cis-[PdI{C6H4(SC6H4R-4}-a)(bpy)] (for example, a = 2, R = H (5)), respectively. Complex 1 (as well as some of its homologues) reacts (1) with 1 equiv of [PdCl2(NCPh)2] to give a mixture of isomers of [{PdBr(PPh3)}2(μ-C,S-C6H4SPh-2)2], (2) with 1 equiv of XyNC (Xy = C6H3Me2-2,6) to render SP-4-4-[PdBr{C,S-C(NXy)C6H4-2-SPh}(PPh3)], (3) with XyNC and TlTfO (TfO = O3SCF3; 1:2:1 molar ratios) to give SP-4-3-[Pd{C,S-C(NXy)C6H4-2-SPh}(CNXy)(PPh3)]TfO, (4) with 4 equiv of XyNC to give SP-4-4-[Pd{C,N-C(NXy)C(NXy)C(NXy)C6H4(SPh)-2}Br(CNXy)], or (5) with TlTfO (1:1 molar ratio) to afford a mixture of compounds from which a few single crystals of (Ph3PC6H4SPh-2)TfO could be obtained. Complexes with bpy ligands react with 2 equiv of PPh3 to give trans-[PdI{C6H4(SC6H4R-4)-4}(PPh3)2] or with 3 equiv of XyNC affording monoinserted complexes resulting from the replacement of the PdI(bpy) group by trans-{C(NXy)}Pd(CNXy)2. Dinuclear complexes are prepared by reacting diiodophenylene thioethers with Pd(dba)2 and bpy. Complex 5 reacts with TlTfO and CO or various alkynes RCCR′ to afford, respectively, [Pd{C,S-C(O)C6H4SPh-2)}bpy]TfO or [Pd{C,S-C(R′)C(R)C6H4SPh-2}bpy], the latter of which decompose thermally to give the benzothiophenes resulting from the C–S coupling. Crystal structures of some model complexes have been determined.