Bonded metal benzothiophene and dibenzothiophene complexes

TABLE 2.4. Known Ti complexes of the benzo- and dibenzo-thiophenes. 

Such structures do not seem to be of great general relevance as HDS models, since they produce activation predominantly of the coordinated benzene ring towards nucleophilic attack [107, 108], For instance, [Mn(CO)3(T -BT)]BF4 reacts with nucleophiles (H , Me, Ef, Ph, CHjCN ) by addition to either the 4- or 7-position of the carbocyclic ring, without any indication of attack to the heterocycle [111]. 

However, some other aspects of the chemistry of ti bonded metal BT and DBT complexes could be of importance in connection with HDS. It is now known, for instance, that 4-methyl- and 4,6-dimethyldibenzothiophene are desulfurized mainly through prior hydrogenation of one or both of the arene rings [46, 112-115], and therefore the study of model ti -DBT complexes could be of use in developing efficient homogeneous, heterogeneous or hybrid catalysts for reducing the arene moieties in this type of molecule either as a pretreatment for conventional HDS, or as an added functionality in novel multimetallic catalyst formulations this possibility is further discussed in Chapter 3. 

Also of interest are Sweigart s recent reports [101-103, 105, 109] showing that some ti -BT or DBT complexes are actually activated toward C-S bond scission by a second metal center, as exemplified in Eq. 2.25. 

These reactions, described in some detail in Chapter 4, illustrate an interesting concept which could be of use in trying to develop bifunctional catalysts specially adapted to the difficult case of desulfurization of methylated dibenzothiophenes and related molecules. 

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Bonded metal benzothiophene and dibenzothiophene complexes Metal j -S-bonded thiophene complexes as adsorbents for the removal of dibenzothiophenes Conclusion... 

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