Organosulfur compounds metal catalysis

Some early proposals for the modes of adsorption of thiophenes on metal sulfides have been probed by comparisons with the structures of well-characterized metal complexes this has allowed the identification of the most reasonable alternatives and of new possibilities not previously considered. Tlieoretical studies on such complexes at increasing levels of sophistication have also contributed in an Important manner to provide a clear and consistent picture of the different possible bonding modes of thiophenes to metal centers. When these theoretical and experimental results from molecular chemistry are combined with the information available from surface techniques and heterogeneous catalysis, the chemisorption of this type of organosulfur compounds on metal sulfides arises as a very well understood phenomenon. This is no doubt one of the most important achievements of the organometallic modeling approach to HDS chemistry. 

The dominant theme since the mid-1980s in the chemistry of thiophenes has undoubtedly been the application of transition metal catalysis. There are two distinct aspects of this work the first is the use of Pd or Ni as catalysts for bond formation. The other is the study of transition metal-mediated ring opening of thiophene by cleavage of S—C bonds. The former is discussed in Section 2.10.4.7. In addition, some mechanistically interesting results have also been reported during this period. These include the preparation of the first fully characterized, stable pentacoordinated sulfur compound with four C—S bonds (Section 2.10.3.1) and the first clear evidence for an organosulfur ate complex (Section 2.10.2.6.4). 

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