Cyclopalladation of telluro ether ligands: synthesis, reactivity and structural characterization.

Treatment of [PdCl2(PhCN)2] with diaryl telluride in 1 : 2 molar ratio gave mononuclear palladium complexes, trans-[PdCl2(TeR2)2] () (R = Mes () (Mes = 2,4,6-trimethylphenyl), Ph (), o-tol () (o-tol = ortho-tolyl)). Reaction of [PdCl2(TeMes2)2] with one equivalent of [PdCl2(PhCN)2] or Na2PdCl4 with TeRR' afforded chloro-bridged binuclear complexes, [Pd2(μ-Cl)2Cl2(TeRR')2] () (R/R' = Mes/Mes (); Mes/Ph (); Ph/Ph ()). A toluene-methanol solution of trans-[PdCl2(TeMes2)2] on refluxing for 30 minutes yielded a binuclear cyclopalladated complex, [Pd2(μ-Cl)2{CH2C6H2(4,6-Me2)TeMes)}2] (). When the refluxing was prolonged, a mononuclear complex cis-[PdCl2{MesTeCH2C6H2(4,6-Me2)TeMes}] () was isolated. Treatment of palladium acetate with TeMes2 afforded an acetato-bridged analogue of , [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)TeMes}2] () together with a very minor component, a tetranuclear complex, [Pd(μ-OAc)(μ-TeMes)]4 (). This reaction with unsymmetrical tellurides, MesTeR, also gave cyclopalladated complexes [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)TeR}2] (R = o-tol () and Ph ()) in which 2-methyl of the mesityl group of the telluride was exclusively metallated. The complex trans-[PdCl2(TeMes2)2] on refluxing in xylene gave palladium telluride, Pd7Te3. These complexes were characterized by elemental analyses, IR and NMR ((1)H, (13)C and (125)Te) spectroscopy. The molecular structures of trans-[PdCl2(TeMes2)2] (), [Pd2(μ-Cl)2Cl2(TeMes2)2]·2acetone (·2acetone), cis-[PdCl2{MesTeCH2C6H2(4,6-Me2)TeMes}] (), [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)TeMes)}2]·toluene (·toluene), [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)Tetol-o}2] () and [Pd(μ-OAc)(μ-TeMes)]4 () were established by single crystal X-ray diffraction analyses. The mononuclear complex was isolated in two polymorphic forms each with the trans configuration.