The Reactivity of Mo(PMe₃)₆ towards Heterocyclic Nitrogen Compounds:  Transformations Relevant to Hydrodenitrogenation

Abstract

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 eta5-pyrrolyl derivative (eta5-pyr)Mo(PMe3)3H, while indole gives sequentially (eta1-indolyl)Mo(PMe3)4H, (eta5-indolyl)Mo(PMe3)3H, and (eta6-indolyl)Mo(PMe3)3H, with the latter representing the first example of a structurally characterized complex with an eta6-indolyl ligand. Likewise, carbazole reacts with Mo(PMe3)6 to give (eta6-carbazolyl)Mo(PMe3)3H with an eta6-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 eta2-pyridyl derivative [eta2-(C5H4N)]Mo(PMe3)4H as a result of alpha-C-H bond cleavage, whereas quinoline and acridine give products of the type (eta6-ArH)Mo(PMe3)3 in which both ligands coordinate in an eta6-manner. For the reaction with quinoline, products with both carbocyclic and heterocyclic coordination modes are observed, namely [eta6-(C6)-quinoline]Mo(PMe3)3 and [eta6-(C5N)-quinoline]Mo(PMe3)3, whereas only carbocyclic coordination is observed for acridine.

Thermally induced inter-ring haptotropic rearrangements in π-complexes of molybdenum with nitrogen containing polyaromatic heterocycles: A DFT study

“…The computed data are in good correspondence with the available experimental structural and kinetic data [26,27]. With PAL = quinoline, the activation barrier is lowered (as compared to its naphthalene analog) by the participation of the nitrogen lone pair to the bonding in the IRHR process, as well as the larger flexibility of the ligand.…”

“…Finally, it is worth to mention that our computed results on these transition complexes of nitrogen-containing PALs, which have been useful in understanding their experimental behavior [26,27], are important for further progress in the investigation of dynamic activity of heterocycle organometallic complexes. In turn this is important for clarifying the role of heteroatom in the barriers of metal movement along the ligand, with respect to catalytic activity.…”

“…This situation changed with the pioneering papers of Parkin and co-workers [26,27] written by Laikov [28]. We used the PBE functional [29], the TZV2P three-exponential basis set of Gauss-type functions for valence electrons [28] (basis set specification: {3,1}/{5,1} for H, {3,3,2}/{5,5,2} for C, N, and P and {5,5,4}/{9,9,8} for Mo), and the TZV2p (SBK-JC) relativistic pseudopotential [30] for core electrons of all the atoms of the molecular systems for which calculations were performed.…”

Synthesis of heteroleptic pyrrolide/bipyridyl complexes of ruthenium(II)

“…However, there are also examples of η 2 coordination to rhenium, tungsten and osmium, 10,11 as well as examples of η 1 complexation to rhenium through the 2-position of pyrrole. 12,13 Although pyrrolide complexes of transition metals such as rhenium 14,15 and molybdenum 16 have been reported, there are few examples reported with ruthenium(II). [17][18][19][20] For example, 18 a pyrrolide ruthenium complex has been observed through the use of a bidentate α-substituted pyrrole, producing N,O-coordinated pyrrolide-ruthenium complexes as models for catalytic intermediates in the Murai coupling reaction (A, Figure 1).…”

Haptotropic migration of M(CO)3 (M=Cr, Mo, W) on substituted phenanthrene

“…It is therefore of interest how the metal influences the energetic course of the rearrangement and if possibly other metals than Cr are more suitable to construct a molecular switch based on haptotropic metal migration [13]. Thermally induced haptotropic migrations of a MoH(PMe 3 ) 3 + group over an indolyl anion as well as of a Mo(PMe 3 ) 3 group over a quinoline unit were already experimentally observed [14]. In the first case the starting compound even could be recovered by photolysis, although not quantitatively.…”