Dinitrogen cleavage and functionalization by carbon monoxide promoted by a hafnium complex

Abstract

Molecular nitrogen (N(2)) and carbon monoxide (CO) have the two strongest bonds in chemistry and present significant challenges in developing new transformations that exploit these two abundant feedstocks. At the core of this objective is the discovery of transition-metal compounds that promote the six-electron reductive cleavage of N(2) at ambient temperature and pressure and also promote new nitrogen-element bond formation. Here we show that an organometallic hafnium compound induces N(2) cleavage on the addition of CO, with a simultaneous assembly of new nitrogen-carbon and carbon-carbon bonds. Subsequent addition of a weak acid liberates oxamide, which demonstrates that an important agrochemical can be synthesized directly from N(2) and CO. These studies introduce an alternative paradigm for N(2) cleavage and functionalization in which the six-electron reductive cleavage is promoted by both the transition metal and the incoming ligand, CO, used for the new bond formations.

Late Metal Scaffolds that Activate Both, Dinitrogen and Reduced Dinitrogen Species NxHy

“…[38][39][40]42,44,46,47,51,52] A few experimental studies showed that a cooperative N 2 activation may even lead to complete N-N bond cleavage. [53][54][55] Notably, iron (a late metal) is present in all three nitrogenase enzyme types, and also the industrial Haber-Bosch process uses iron-based catalysts for N 2 reduction. As mentioned above, due to the inefficient π-backbonding late metal N 2 complexes typically achieve only a moderate N-N weakening, but apparently, strong activation is not necessarily a requirement for nitrogen fixation.…”

Activation of Dinitrogen‐Derived Hafnium Nitrides for Nucleophilic NC Bond Formation with a Terminal Isocyanate

“…Inspired by reports by Sobota [2] and Fryzuk, [3] our laboratory has been exploring "ligand-induced N 2 cleavage", whereby a reducing transition metal is combined with an incoming ligand to supply the requisite six electrons to cleave the NN bond. [4] With strongly activated zirconocene [5] and hafnocene [6] dinitrogen complexes, this approach has proven to be a general method for nitrogen-carbon bond formation using carbon monoxide as the incoming ligand.…”

Insights into the Cascade Reaction of CO and Heteroallenes Mediated by Dinitrogen Hafnocene Complexes: The Indirect Effect of Nitride's Nucleophilicity

“…This is al ow-energy process, havinga na ctivation barrier of almost 2kcal mol , which can be better described as ar etro-[2+ +2] cycloaddition transitions tate. [3,7] The strong activation of the NÀNb ond in 3 gives rise to an easy bond scission, implying an enthalpy activation barrier of only 4.9 kcal mol…”

“…[2] In particular,c arbonylation of N 2 to form nitrogencarbon bonds is possible, but rare, the first example of which used ansa-hafnocene complexes,a sr eported by Chirik and coworkers. [3] Such complexes can effect the formation of various importantN -containingo rganic ligands,s uch as oxamidides [4] and m-formamides. [5] The formation of an itride intermediate in this type of reaction was also confirmed by kinetics studies reported by the same group.…”