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

Phenylene thioethers XC 6 H 4 (SC 6 H 4 R-4)- a ( a = 2, 4; X = Br, I; R = H, OMe, NO 2 ) react with Pd(dba) 2 and 2 equiv of PPh 3 or 1 equiv of 2,2′-bipyridine (bpy) to afford trans -[PdBr{C 6 H 4 (SC 6 H 4 R-4)- a }(PPh 3 ) 2 ] (for example, a = 2, R = H ( 1 )) or cis -[PdI{C 6 H 4 (SC 6 H 4 R-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 [PdCl 2 (NCPh) 2 ] to give a mixture of isomers of [{PdBr(PPh 3 )} 2 (μ- C,S -C 6 H 4 SPh-2) 2 ], (2) with 1 equiv of XyNC (Xy = C 6 H 3 Me 2 -2,6) to render SP-4-4- [PdBr{ C,S -C(═NXy)C 6 H 4 -2-SPh}(PPh 3 )], (3) with XyNC and TlTfO (TfO = O 3 SCF 3; 1:2:1 molar ratios) to give SP-4-3- [Pd{ C,S -C(═NXy)C 6 H 4 -2-SPh}(CNXy)(PPh 3 )]TfO, (4) with 4 equiv of XyNC to give SP-4-4- [Pd{ C,N -C(═NXy)C(═NXy)C(═NXy)C 6 H 4 (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 (Ph 3 PC 6 H 4 SPh-2)TfO could be obtained. Complexes with bpy ligands react with 2 equiv of PPh 3 to give trans -[PdI{C 6 H 4 (SC 6 H 4 R-4)-4}(PPh 3 ) 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)C 6 H 4 SPh-2)}bpy]TfO or [Pd{ C,S -C(R′)═C(R)C 6 H 4 SPh-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.