SYNTHESIS AND PROPERTIES OF 2-SUBSTITUTED OR 2,5-SUBSTITUTED THIOPHENE AND 2-SUBSTITUTED OR 2,5'-SUBSTITUTED DITHIOPHENE DERIVATIVES OF PLATINUM

The reaction of [PtCl2(COD)] (COD = cycloocta-1,5-diene) with 2,5-bis(trimethylstannyl)thiophene or with 2,5'-bis(trimethylstannyl)-5-(2'-thienyl)thiophene gives diplatinum complexes bridged with 2,5-thienylene or 2,5'-di(5,2'-thienylene), [CI(COD)Pt(mu-2,5-C4H2S)Pt(COD)Cl] (1) and [Cl(COD)Pt(mu-2,5'-C4H2S-C4H2S)Pt(COD)Cl] (4). On treatment with tri-n-butylphosphine these give the corresponding tributylphosphine derivatives, trans,trans-[CI(PBU3)2Pt(mu-2,5-C4H2S)Pt(PBU3)2Cl] (2) and trans,trans-[Cl(PBU3)2Pt(mu-2,5'-C4H2S-C4H2S)Pt(PBu3)2Cl] (5), respectively. Treatment of 2 with 2-thienyllithium in THF gives trans,trans-[(2-C4H3S)(PBu3)2Pt(mu-2,5-C4H2S)Pt(PBU3)2(2-C4H3S)](3). The di-2-thienyl and bis-2-dithienyl complexes, [M(2-C4H3S)2(PBu3)2] (6) and [M{5-(2'-C4H3S)-2C4H2S}2(PBu3)2] (M = Pt (7a), Pd (7b), Ni (7c)), have also been prepared by treatment of [M(PBu3)2X2] (X = Cl or Br) with 2-thienyllithium and 5-(2'-thienyl)-2-thienyllithium in THF. The electronic spectra of the above complexes contain metal to ligand charge transfer bands, suggesting that d(pi)-p(pi) interaction between two platinum atoms through thienylene groups appears to play an important role.