Model complexes for metallated polythiophenes: Gold(I) and palladium(II) complexes of bis(diphenylphosphino)oligothiophenes

The preparations of two new phosphinothiophene ligands, 3,3'-bis(diphenylphosphino)-2,2'-bithiophene (dppbt; 1) and 3,3{''}'-dihexyl-3',3{''}-bis(diphenylphosphino)-2,5':2',2{''}:5{''},2{' '}'-quate hiophene(hdppqt; 2) are reported, Oxidation of I gives 3,3'-bis(diphenylphosphine oxide)-2,2'-bithiophene (3), and the crystal structure of this compound was determined. Pd(II) and Au(I) complexes of these ligands have been synthesized and characterized, Crystal structures of {[}(dppbt)PdCl2] (I-Pd), {[}(hdppqt)PdCl2] (2-Pd), {[}(dppbt)(AuCl)(2)] (1-Au), and {[}(hdppqt)(AuCl)(2)](2-Au) were obtained. {[}(dppbt)(AuCl)(2)] crystallized in two solid-state forms; crystals grown from CH2Cl2/Et2O show a gold-gold interaction of 3.3221(4) Angstrom, but from CH2Cl2/toluene, the molecule crystallizes as a toluene adduct (1-Au-tol) and does not show any gold-gold interaction. All the complexes were characterized via UV-vis spectroscopy and cyclic voltammetry, and the effect of the metal on the energy of the pi-pi{*} transition and oxidation potential was determined, These data are correlated to the interannular torsion angles in the oligothienyl groups from the crystal structure studies.