Carbon−Sulfur Bond Cleavage and Hydrodesulfurization of Thiophenes by Tungsten

The reactions of W(PMe3)4(η2-CH2PMe2)H, W(PMe3)5H2, W(PMe3)4H4 and W(PMe3)3H6 towards thiophenes reveal that molecular tungsten compounds are capable of achieving a variety of transformations that are relevant to hydrodesulfurization. For example, sequential treatment of W(PMe3)4(η2-CH2PMe2)H with thiophene and H2 yields the butanethiolate complex, W(PMe3)4(SBun)H3, which eliminates but-1-ene at 100 °C. Likewise, sequential treatment of W(PMe3)4(η2-CH2PMe2)H with benzothiophene and H2 yields W(PMe3)4(SC6H4Et)H3, which releases ethylbenzene at 100 °C. Moreover, W(PMe3)4(η2-CH2PMe2)H desulfurizes dibenzothiophene to form a dibenzometallacyclopentadiene complex, [(κ2-C12H8)W(PMe3)](μ-S)(μ-CH2PMe2)(μ-PMe2)[W(PMe3)3].

四(三甲基膦)(η²-亚甲基二甲基膦)氢化钨[W(PMe₃)₄(η²-CH₂PMe₂)H]、五(三甲基膦)二氢化钨[W(PMe₃)₅H₂]、四(三甲基膦)四氢化钨[W(PMe₃)₄H₄]与三(三甲基膦)六氢化钨[W(PMe₃)₃H₆]与噻吩类底物的反应研究表明，分子态钨化合物可实现多种与加氢脱硫（hydrodesulfurization）相关的转化过程。例如，将W(PMe₃)₄(η²-CH₂PMe₂)H先后与噻吩及氢气反应，可得到正丁硫醇盐配合物W(PMe₃)₄(SBun)H₃，该配合物在100 ℃下可脱除1-丁烯。类似地，将W(PMe₃)₄(η²-CH₂PMe₂)H先后与苯并噻吩及氢气反应，可得到配合物W(PMe₃)₄(SC₆H₄Et)H₃，该配合物在100 ℃下可释放乙苯。此外，W(PMe₃)₄(η²-CH₂PMe₂)H可使二苯并噻吩发生脱硫反应，生成二苯并金属环戊二烯配合物[(κ²-C₁₂H₈)W(PMe₃)](μ-S)(μ-CH₂PMe₂)(μ-PMe₂)[W(PMe₃)₃]。