Fixation of Dinitrogen at an Asymmetric Binuclear Titanium Complex

Abstract

A new type of dititanium dinitrogen complex supported by a triphenolamine (TPA) ligand is reported. Analysis by single-crystal X-ray diffraction and Raman and NMR spectroscopy reveals different coordination geometries for the two titanium centers. Hence, coordination of TPA and a nitrogen ligand results in trigonal-bipyramidal geometry, while an octahedral titanium center is obtained upon additional coordination of an ethoxide generated upon C–O bond cleavage in a diethyl ether solvent molecule. The titanium complex successfully generates ammonia in the presence of an excess amount of PCy3HI and KC8 in 154% yield (per titanium atom). A titanium complex with a bulkier TPA does not form a dinitrogen complex, and mononuclear titanium dinitrogen complexes were not accessible, presumably because of the high tendency of early transition metals to form binuclear dinitrogen complexes.

Dinitrogen Functionalization with Carbon Dioxide and Carbon Disulfide Giving Symmetric and Unsymmetric Hydrazido Complexes

“…Each potassium ion is further coordinated by a DME molecule. The Ti 2 K 2 N 2 core in 2 resembles the reported structure for triamidoamine and triaryloxide-amine complexes, [20,21] in which the N 2 ligand binds end-on to the Ti centers and side-on to the K centers. The TiÀ NÀ NÀ Ti linkage of 2 is almost linear (TiÀ NÀ N = 174.5(2)°), and the long NÀ N bond length of 1.299(3) Å is comparable to other reduced dinitrogen complexes of titanium.…”

Direct Incorporation of Dinitrogen into an Aliphatic C–H Bond

“…Simultaneous with dinitrogen reduction, the butoxide ligand, which was derived from the THF ring opening, bonded to each titanium center trans to the amine nitrogen of the [N 2 N] 2– ligand. Activation of the C–O bond in ethers under reducing conditions for group IV metal complexes were previously reported in the literatures. − Recently, Lee and coworkers also observed that titanium can promote C–O bond cleavage in diethyl ether during the N 2 fixation process . In order to further identify the bridging atom as a nitride, the degradation experiments were carried out by treating complex 15 with HCl/Et 2 O solution, and NH 4 Cl was afforded in 88% yield, quantified by 1 H NMR.…”

Ring-Opening Copolymerization Using a Chromium Complex with a Readily Available Aminotriphenolate Ligand

“…19 Although the Kleij group achieved the synthesis of the octahedral chromium(III) complex with sterically less bulky aminotriphenolate ligand and 4-dimethylaminopyridine (DMAP), 19 this is in contrast to the vast majority of early transition metal aminotriphenolate complexes including 1 (Figure 1), which have trigonal bipyramidal (TBP) geometry regardless of the ligands' steric bulkiness. 20,21 The Cr−O bond distances of 2 are longer than in 1, but the Cr−N bond distance is almost identical to that of 1 (Table S3). Two tetrahydrofuran molecules (THFs) coordinate at the Cr(III) center to stabilize the complex.…”