The synthesis of N-heterocycles is of paramount importance for the pharmaceutical industry. They are often synthesized through atom economic and environmentally unfriendly methods, generating significant waste. A less explored, but greener, alternative is the synthesis through the direct intramolecular C–H amination utilizing organic azides. Few examples exist by using this method, but many are limited due to the required use of stoichiometric amounts of Boc2O. Herein, we report a homoleptic C,O-chelating mesoionic carbene–iron complex, which is the first iron-based complex that does not require the addition of any protecting groups for this transformation and that is active also in strong donor solvents such as THF or even DMSO. The achieved turnover number is an order of magnitude higher than any other reported catalytic system. A variety of C–H bonds were activated, including benzylic, primary, secondary, and tertiary. By following the reaction over time, we determined the presence of an initiation period. Kinetic studies showed a first-order dependence on substrate concentration and half-order dependence on catalyst concentration. Intermolecular competition reactions with deuterated substrate showed no KIE, while separate reactions with deuterium-labeled substrate resulted in a KIE of 2.0. Moreover, utilizing deuterated substrate significantly decreased the initiation period of the catalysis. Preliminary mechanistic studies suggest a unique mechanism involving a dimeric iron species as the catalyst resting state.

A high-spin, mononuclear TiII complex, [(Tp tBu,Me)­TiCl] [Tp tBu,Me– = hydridotris­(3-tert-butyl-5-methylpyrazol-1-yl)­borate], confined to a tetrahedral ligand-field environment, has been prepared by reduction of the precursor [(Tp tBu,Me)­TiCl2] with KC8. Complex [(Tp tBu,Me)­TiCl] has a 3A2 ground state (assuming C 3v symmetry based on structural studies), established via a combination of high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy, solution and solid-state magnetic studies, Ti K-edge X-ray absorption spectroscopy (XAS), and both density functional theory and ab initio (complete-active-space self-consistent-field, CASSCF) calculations. The formally and physically defined TiII complex readily binds tetrahydrofuran (THF) to form the paramagnetic adduct [(Tp tBu,Me)­TiCl­(THF)], which is impervious to N2 binding. However, in the absence of THF, the TiII complex captures N2 to produce the diamagnetic complex [(Tp tBu,Me)­TiCl]2(η1,η1;μ2-N2), with a linear TiNNTi topology, established by single-crystal X-ray diffraction. The N2 complex was characterized using XAS as well as IR and Raman spectroscopies, thus establishing this complex to possess two TiIII centers covalently bridged by an N2 2– unit. A π acid such as CNAd (Ad = 1-adamantyl) coordinates to [(Tp tBu,Me)­TiCl] without inducing spin pairing of the d electrons, thereby forming a unique high-spin and five-coordinate TiII complex, namely, [(Tp tBu,Me)­TiCl­(CNAd)]. The reducing power of the coordinatively unsaturated TiII-containing [(Τp tBu,Me)­TiCl] species, quantified by electrochemistry, provides access to a family of mononuclear TiIV complexes of the type [(Tp tBu,Me)­TiE­(Cl)] (with E2– = NSiMe3, N2CPh2, O, and NH) by virtue of atom- or group-transfer reactions using various small molecules such as N3SiMe3, N2CPh2, N2O, and the bicyclic amine 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]­hepta-2,5-diene.

Using the potentially tridentate N,N’-bis(N-heterocyclic silylene)pyridine [SiNSi] pincer-type ligand, 2,6-N,N’-diethyl-bis[N,N’-di-tert-butyl(phenylamidinato)silylene] diaminopyridine, led to the first isolable bis(silylene)pyridine-stabilized manganese(0) complex, {к3-[SiNSi]Mn(dmpe)} 4 (dmpe = (Me2P)2C2H4), which represents an isolobal 17 VE...

Addition of the bipyridyl‐embedded cycloparaphenylene nanohoop bipy[9]CPP to [Fe{H2B(pyz)2}] (pyz=pyrazolyl) produces the distorted octahedral complex [Fe(bipy[9]CPP){H2B(pyz)2}2] (1). The molecular structure of 1 shows that the nanohoop ligand contains a non‐planar bipy unit. Magnetic susceptibility measurements indicate spin‐crossover (SCO) behaviour with a T1/2 of 130 K, lower than that of 160 K observed with the related compound [Fe(bipy){H2B(pyz)2}2] (2), which contains a conventional bipy ligand. A computational study of 1 and 2 reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop.

The synthesis of a tripodal, S-based ligand, namely the mesitylene-anchored, tris-thiophenolate-functionalized (mes-( Me,Ad ArS) 3 ) 3− (1) 3− , and its coordination chemistry with lowvalent uranium to form [U III ((SAr Ad,Me ) 3 mes)] (1-U) are reported. Single-crystal X-ray diffraction analysis reveals a C 3 -symmetric molecular structure. Full characterization of 1-U was performed using nuclear magnetic resonance, UV−vis−NIR electronic absorption, and electron paramagnetic resonance spectroscopies as well as SQUID magnetometry, thus confirming the U(III) oxidation state. Alternating current magnetic studies show that 1-U exhibits single-molecule magnet behavior at low temperatures in a non-zero external field. Comparison of these results to those of the previously reported mesitylene-anchored complexes, [U III ((OAr Ad,Me ) 3 mes)] and [U III ((OAr tBu,tBu ) 3 mes)], indicates a drastic change in the electronic structure when moving from phenolate-based ligands to thiophenolate-based 1, which is further discussed by means of computational analysis (NBO, DFT, and QTAIM). Despite the U−O bonds being stronger, a much higher covalency was found for the U−S analogue. Article pubs.acs.org/IC