Model Complexes for Metallated Polythiophenes: Gold(l) and Palladium(ll) Complexes of Bis(diphenylphosphino)oligothiophenes

The preparations of two new phosphinothiophene ligands, 3,3ʹ-bis(diphenylphosphino)-2,2ʹ-bithiophene (dppbt; 1) and 3,3ʹʹʹ-dihexyl-3ʹ,3"-bis(diphenylphosphino)-2,5ʹ:2ʹ,2":5",2ʹ"-quaterthiophene (hdppqt; 2) are reported. Oxidation of 1 gives 3,3ʹ-bis(diphenylphosphine oxide)-2,2ʹ-bithiophene (3), and the crystal structure of this compound was determined. Pd(ll) and Au(l) complexes of these ligands have been synthesized and characterized. Crystal structures of [(dppbt)PdCl2] (1-Pd), [(hdppqDPdCl2 (2-Pd), [(dppbt)(AuCl)2] (1-Au), and [(hdppqt)(AuCI)2] (2-Au) were obtained. [(dppbt)(AuCI)2] crystallized in two solid-state forms; crystals grown from CH2Cl2/Et2O- show a gold-gold interaction of 3.3221(4) A, 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 Adata are correlated to the interannular torsion angles in the oligothienyl groups from the crystal structure studies.