Cyclopalladated N,N-dimethylthiophene-2- and -3-carboselenoamide derivatives

N,N-Dimethylthiophene-2- and -3-carboselenoamides, abbreviated as Hats and Hbts, respectively, were easily obtained by the reaction of the corresponding carboxamide with phenyldichlorophosphine selenide. Hats and Hbts reacted with lithium tetrachloropalladate in methanol to give [PdCl(ats)]₂ and [PdCl(bts)]₂, respectively. Several derivatives of the two were prepared with ligands (L) such as pyridine (py) or tri-n-butylphosphine (PBu₃). The new compounds were characterized spectroscopically and the structures of [PdCl(bts)(PBu₃)] and [PdCl(ats)(tbp)] (tbp=4-tert-butylpyridine) were determined by X-ray analysis. The former was shown to be a trans-(C, Cl) isomer, while the latter a cis-(C, Cl) one, where C represents the palladated carbon atom. Hats was palladated at position 3 of the thiophene ring and Hbts exclusively at position 2 of the ring. The selenoamide group was coordinated through the selenium atom to form a five-membered palladaselenaheterocycle. The trans influence of a trans donor was reflected in the PdSe bonds: 2.4147(8) Å (trans to PBu₃) in [PdCl(bts)(PBu₃)] and 2.359(1) Å (trans to Cl) in [PdCl(ats)(tbp)].