Synthesis of Collidine from Dinitrogen via a Tungsten Nitride

Abstract

The synthesis of pyridines from dinitrogen in homogeneous solution is known to be challenging considering that an N 2 cleavage step needs to be combined with two N−C coupling steps. Herein, a tungsten complex bearing a tailor-made 2,2′-( t Bu 2 As) 2 -substituted tolane ligand scaffold was shown to split N 2 to afford the corresponding tungsten nitride, which is not the case for the corresponding ( i Pr 2 As) 2 -substituted derivative. The former nitride was then reacted with 2,4,6-trimethylpyrylium triflate, which led to the formation of a tungsten oxo complex, along with collidine. Over the course of this reaction, the O atom of the pyrylium starting material was replaced with an N atom via a hitherto unprecedented skeletal editing process.

Origin of Reactivity Trends of an Elusive Metathesis Intermediate from NMR Chemical Shift Analysis of Surrogate Analogues

“…Moreover, 1 (166 Hz) and 2 (148 Hz) show reduced 1 J ( 183 W– 13 C CH 2 /CH ) than 3 (221 Hz), in accord with the decreased W–C bond order and reduced s -character of the sp 2 -hybridyzed methylidene carbon. In addition to the standard set of data, taking advantage of 2 J couplings between proton/s at the methylidyne/dene ligands and 183 W, we collected 2D 1 H– 183 W HMBC spectra and extracted isotropic chemical shifts for 183 W in high-valent W­(VI) species. − Similar measurements for W­(IV) complex 1 were unfruitful due to the absence of J -couplings of adequate strength. The 183 W in the oxo-methylidyne 3 resonates at 405 ppm, which is in the range measured for highly Lewis-acidic tripodal W–carbyne complexes within three siloxide or fluorinated alkoxide ligands .…”

Monomethylation and -protonation of Lutetium Dinitrogen Complex

“…Significant achievements have been made in the activation and transformation of dinitrogen via transition metal (TM)–dinitrogen complexes over the past century. − Due to the unique electronic structures, rare earth (RE) dinitrogen complexes can exhibit reactivity different from the main group − and transition metals. − In contrast with the even-electron reduction (TM-(N 2 ) n − , n = 2, 4, 6) in transition metal dinitrogen complex, the odd-electron reduction species (N 2 ) 3– has been confirmed in rare earth dinitrogen complex by William Evans and colleagues since 2009. − Further EPR investigation and DFT calculations confirmed the radical property of (N 2 ) 3– . These features may relate to the restricted valencies of rare earth metal centers and the polarization of the RE–N bond. ,, In comparison with the rich reactivity of TM-(N 2 ) comlexes, − only two examples of (N 2 ) 3– functionalization have been reported. Reaction of {[(Me 3 Si) 2 N] 2 (THF)­RE} 2 ­(μ 2 -η 2 :η 2 -N 2 ) (RE = Y, Gd) with [Et 3 NH]­[BPh 4 ] led to the biprotonated ((N 2 H 2 ) 2– ) products {[(Me 3 Si) 2 N] 2 ­(THF)­RE} 2 ­(μ-N 2 H 2 ) (RE = Y, Gd) .…”

Hydrazido complexes prepared by methylation of an anionic end-on bridging dinitrogen dititanium complex

“…1 The construction of nitrogen–carbon bonds from coordinated N 2 is especially appealing, because this process is a key step in the conversion of N 2 into organonitrogen compounds directly without going through ammonia as an intermediate. 2 Making hydrazine derivatives using such an approach is also attractive for the direct use of N 2 with the N–N bond retention due to the production of parent hydrazine (N 2 H 4 ) relying on the oxidative coupling of NH 3 . 3…”