C-S bond activation and partial hydrogenation of thiophene by a dinuclear trihydride platinum complex

Ainara Nova, Fernando Novio, Pilar González-Duarte, Agustí Lledós, Rubén Mas-Ballesté

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16 Citations (Scopus)

Abstract

[(dppp)2Pt2H3]ClO4 [I, dppp = Ph2P(CH2)3PPh2] was found to activate the C-S bond and to cause partial hydrogenation of thiophene. Thus, the reaction of I with neat thiophene (T) at reflux temperature yields [(dppp)Pt(SC4H4-C,S)] (II) and [(dppp)2Pt 2(μ-SC4H5-C,S)]ClO4 (III) at a 2:3 molar ratio. The same reaction in toluene or benzene solvent affords the same complexes II and III but in a 1:9 molar ratio. The concomitant formation of II and III was interpreted on the basis of theoretical calculations (DFT), which have provided a detailed insight into the reaction mechanism. Thus, the presence of T causes I to dissociate into [(dppp)PtH2] and [(dppp)-PtH(C4H4S-κS)], this process being a common step for the two ensuing reaction pathways. After dissociation, the activation of the thiophene C-S bond to yield II involves participation of [(dppp)PtH 2] exclusively. However, the reaction leading to III requires the internal migration of the coordinated hydride to the thiophene ligand in [(dppp)PtH(C4H4S-κS)] and the subsequent assistance of the {(dppp)Pt} fragment formed from [(dppp)PtH2] by hydrogen elimination. As a result of the involvement of [(dppp)PtH2] in the formation of both II and III, the two reaction pathways are competitive. The reactivity of II and III with various sources of hydride ligands and different protonic acids has also been examined. Thus, the reaction of II with HBF 4 leads to the thiolate-bridged dinuclear complex [(dppp) 2Pt2(μ-SC4H5)2] (BF4)2 (IV). In the case of III the addition of HBF 4 leads to [(dppp)2-Pt2(μ-SC 4H6)](BF4)2 (V), which transforms into III by the addition of a base. The X-ray structural characterization of the unprecedented complex V is reported here. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Original languageEnglish
Pages (from-to)5707-5719
JournalEuropean Journal of Inorganic Chemistry
Issue number36
DOIs
Publication statusPublished - 1 Dec 2007

Keywords

  • C-S activation
  • Desulfurization
  • Hydride ligands
  • Platinum
  • Reaction mechanisms
  • Thiophene

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