Oligomerization of thiophene in the presence of PdCl42-

Article abstract of DOI:10.1016/0022-328X(91)83132-N

In the presence of PdCl4^2- in alcohol/water solution, thiophene oligomerized to form α,α-coupled bithiophene while 2,2'-bithiophene oligomerized to form α,α-coupled tetrathiophene as the major products.In the case of thiophene, two unstable intermediates were isolated and characterized by 1H NMR as η¹,C-bonded and η⁵,?-bonded thiophene-palladium(II) complexes.The mechanism of Α,α-coupling of is thus proposed.