The reactivity of Mo(PMe3)6 towards heterocyclic nitrogen compounds:: Transformations relevant to hydrodenitrogenation

The reactions of Mo(PMe3)6 towards a variety of five- and six-membered heterocyclic nitrogen compounds (namely, pyrrole, indole, carbazole, pyridine, quinoline, and acridine) have been studied to provide structural models for the coordination of these heterocycles to the molybdenum centers of hydrodenitrogenation catalysts. Pyrrole reacts with Mo(PMe3)6 to yield the η5-pyrrolyl derivative (η5-pyr)Mo(PMe3)3H, while indole gives sequentially (η1-indolyl)Mo(PMe3)4H, (η5-indolyl)Mo(PMe3)3H, and (η6-indolyl)Mo(PMe3)3H, with the latter representing the first example of a structurally characterized complex with an η6-indolyl ligand. Likewise, carbazole reacts with Mo(PMe3)6 to give (η6-carbazolyl)Mo(PMe3)3H with an η6-carbazolyl ligand. The reactions of Mo(PMe3)6 with six-membered heterocyclic nitrogen compounds display interesting differences in the nature of the products. Thus, Mo(PMe3)6 reacts with pyridine to give an η2-pyridyl derivative [η2-(C5H4N)]Mo(PMe3)4H as a result of α-C-H bond cleavage, whereas quinoline and acridine give products of the type (η6-ArH)Mo(PMe3)3 in which both ligands coordinate in an η6-manner. For the reaction with quinoline, products with both carbocyclic and heterocyclic coordination modes are observed, namely [η6-(C6)-quinoline]Mo(PMe3)3 and [η6-(C5N)-quinoline]Mo(PMe3)3, whereas only carbocyclic coordination is observed for acridine. Copyright © 2002 American Chemical Society.