Synthesis and characterization of palladium(II) complexes with aryl tellurols and diaryl ditellurides

Abstract

Polymeric complexes of formula [PdCl(TeAr)] n ( I) and [Pd(TeAr) 2] n ( II) are readily obtained by the reaction between Na 2[PdCl 4] and NaTeAr (ArC 6H 5, C 6H 4OCH 3−4 and C 6H 4OCH 2CH 3−4) in ethanol at room temperature. Chemical and far infrared spectral evidences support alternating chloride and tellurol bridges in I and tellurol bridges in II. While the reaction of I (AtC 6H 4OCH 3−4) with PPh 3 in stoichiometric amount results in splitting of chloride bridges and formation of a tellurol bridged dimeric complex [PdCl(TeC 6H 4OCH 3−4)(PPh 3)] 2 ( III), with excess of PPh 3, cleavage of both chloride and tellurol bridges leads to the formation of a monomeric compound [PdCl(TeC 6H 4OCH 3−4)(PPh 3) 2] ( IV). Furthermore, the reaction of I (Ar C 6H 4OCH 2CH 3−4) with 1,2-bis(diphenyl phosphino)ethane in equimolar ratio also resulted in a monomeric compound [(PdCl(TeC 6H 4OCH 2CH 3−4)(diphos)] ( V). The complex III (ArC 6H 4OCH 2CH 3−4) is also prepared by the reaction between Pd(PPh 3) 2Cl 2 and Ph 3SnTeC 6H 4OCH 2CH 3−4 in 1:1 molar ratio or between Pd 2Cl 4(PPh 3) 2 and Ph 3SnTeC 6H 4OCH 2CH 3−4 in 1:2 molar ratio in benzene at room temperature. Sodium tetrachloropalladate reacts readily with diarylditellurides in ethanol at 0 °C to form dimeric complexes [PdCl 2(ArTeTeAr)] 2 ( VI). However, at 40 °C or above the same ditellurides form polymeric complexes I with Na 2[PdCl 4] in ethanol. The complex VI is also obtained by the reaction of Pd(PhCN) 2Cl 2 with Te 2Ar 2 in benzene at room temperature. The complexes were characterized by elemental analysis, IR, Raman and 1H NMR spectra and, where possible, by conductivity measurements and molecular weight determinations.