An Isolable Azide Adduct of Titanium(II) Follows Bifurcated Deazotation Pathways to an Imide

Abstract

AdN3 (Ad = 1-adamantyl) reacts with the tetrahedral TiII complex [(Tp tBu,Me)­TiCl] (Tp tBu,Me = hydrotris­(3-tert-butyl-5-methylpyrazol-1-yl)­borate) to generate a mixture of an imide complex, [(Tp tBu,Me)­TiCl­(NAd)] (4), and an unusual and kinetically stable azide adduct of the group 4 metal, namely, [(Tp tBu,Me)­TiCl­(γ-N3Ad)] (3). In these conversions, the product distribution is determined by the relative concentration of reactants. In contrast, the azide adduct 3 forms selectively when a masked TiII complex (N2 or AdNC adduct) reacts with AdN3. Upon heating, 3 extrudes dinitrogen in a unimolecular process proceeding through a titanatriazete intermediate to form the imide complex 4, but the observed thermal stability of the azide adduct (t 1/2 = 61 days at 25 °C) is at odds with the large fraction of imide complex formed directly in reactions between AdN3 and [(Tp tBu,Me)­TiCl] at room temperature (∼50% imide with a 1:1 stoichiometry). A combination of theoretical and experimental studies identified an additional deazotation pathway, proceeding through a bimetallic complex bridged by a single azide ligand. The electronic origin of this deazotation mechanism lies in the ability of azide adduct 3 to serve as a π-backbonding metallaligand toward free [(Tp tBu,Me)­TiCl]. These findings unveil a new class of azide-to-imide conversions for transition metals, highlighting that the mechanisms underlying this common synthetic methodology may be more complex than conventionally assumed, given the concentration dependence in the conversion of an azide into an imide complex. Lastly, we show how significantly different AdN3 reacts when treated with [(Tp tBu,Me)­VCl].

Tale of Three Molecular Nitrides: Mononuclear Vanadium (V) and (IV) Nitrides As Well As a Mixed-Valence Trivanadium Nitride Having a V3N4 Double-Diamond Core

“…It further suggests that the reaction of 1 with NaN 3 traverses two transmetallation steps before N 2 extrusion ensues. We have no definitive reason why complex 4 , as opposed to A , would be reluctant to undergo N 2 elimination, but based on previous studies, we speculate that an azide ligand bridging across two V centers might play a critical role. , …”

Benzimidazole-diamide (bida) Pincer Chromium Complexes: Structures and Reactivity

“…From Evans’ method measurements, a value of μ eff of 3.1 μ B was obtained, consistent with an S T = 3/2 center significantly attenuated by spin−orbit effects. It may be that γ-coordination of ArNNN must occur prior to N 2 loss, ,− and if the adjacent position to azide binding is a chloride, reversible α- to γ-coordination can occur. If an alkyl is present, an alternative, swifter path to insertion is present and N 2 loss is averted.…”

A Borane Lewis Acid in the Secondary Coordination Sphere of a Ni(II) Imido Imparts Distinct C–H Activation Selectivity

“…Group transfer from azides to low valent metal centers is a common strategy to prepare metal imido complexes, including related NiNR compounds reported by Hillhouse . Prior to N 2 extrusion, several metal azide complexes, either in η 1 -N γ or η 2 -N β /N γ coordination modes, have been isolated as intermediates. , To access nickel imido complexes with an appended borane and study their subsequent reactivity, we evaluated reactions between 3 and representative aryl and alkyl azides.…”

“…40 Prior to N 2 extrusion, several metal azide complexes, either in η 1 -N γ or η 2 -N β /N γ coordination modes, have been isolated as intermediates. 68,69 To access nickel imido complexes with an appended borane and study their subsequent reactivity, we evaluated reactions between 3 and representative aryl and alkyl azides.…”