Treatment of [((tBu)pyrr(2)pyr)Fe(OEt2)] (1-OEt2) ((tBu)pyrr(2)pyr(2-) = 3,5-Bu-t(2)-bis(pyrrolyl)pyridine) with trimethylsilyl azide (N3SiMe3) and subsequent photolysis at 390 nm results in clean formation of [((tBu)pyrrpyrpyrrNHSiMe(3))Fe] (2) as the result of a nitrene being inserted into a tert-butyl C-H bond of the (tBu)pyrr(2)pyr ligand. Treatment of 1-OEt2 with azidotrimethyltin (N3SnMe3), however, results in isolation of the gamma-bound azide adduct ferrous complex, [((tBu)pyrr(2)pyr) Fe(N3SnMe3)] (1-N3SnMe3). When treated with diphenyl diazomethane (Ph2CN2), complex 1-OEt2 converts to the iron carbene complex [((tBu)pyrr(2)pyr)FeCPh2] (1-CPh2), and the X-ray structure revealed a Fe-CPh2 bond length of 1.964(3) angstrom. A room temperature magnetic moment of 1-CPh2 indicates an S = 2 spin state, consistent with a high-spin Fe-III center antiferromagnetically coupled to a carbene radical anion (CPh2 center dot-). Zero-field Fe-57 Mossbauer spectroscopy and Fe K-edge X-ray absorption spectroscopy confirm this assignment. In solution, complex 1-CPh2 rearranges to [{(tBu)pyrrpyrC(=CPh2)-C(CMe3)=CH-C(CMe3)=N}Fe](2) (3) resulting from carbene insertion into the 1-position of the pyrrolide arm of the (tBu)pyrr(2)pyr ligand and dimerization. Complex 3 possesses two high-spin Fe-II centers according to Fe-57 Mossbauer spectroscopy, with antiferromagnetic coupling between the spin centers. Monitoring the conversion of 1-CPh2 to 3 by UV-vis spectroscopy reveals this process to be first order in 1-CPh2 with a highly ordered transition state evidenced by activation parameters: Delta S-double dagger = -87.6 +/- 25.8 J.mol(-1).K-1 and Delta H-double dagger = 63.1 +/- 8.3 kJ.mol(-1).

Treatment of the ligand precursor H3TIMMNMesCl3 (TIMMNMes = tris-[(3-mesityl-imidazol-2-ylidene)methyl]amine) with an excess of base yields the literature-known ferrous tris-N-heterocyclic carbene (NHC) complex [(TIMMNMes)FeIICl]Cl (1-Cl). In contrast, utilizing a substoichiometric amount of base initiates a unique rearrangement of all three NHC pendant arms to yield the tripodal, all-N-bound tris-imidazole [(N-TIMMNMes)FeIICl]Cl (2-Cl sol ). Divalent 2-Cl and 2-PF 6 are fully characterized, structurally by single-crystal X-ray diffraction analysis and spectroscopically by 1H NMR and 57Fe Mossbauer spectroscopy as well as SQUID magnetization measurements, to demonstrate the influence of the change from a soft strong-field to a hard weak-field ligand. Optimized reaction conditions for the reproducible, high-yield carbene-to-imidazole rearrangement were developed in a series of experiments.

Reduction of [K2{(tBupyrr2pyr)Fe}2(mu-N2)] (1) with two equiv. of KC8 in the presence of crown-ether 18-C-6 yields the N2 adduct [{K(18-C-6)}2(tBupyrr2pyr)Fe(N2)] (2). Complex 2 heterolytically splits the Csp2-H bond of benzene to form [{K(18-C-6)}(tBupyrr2pyr)Fe(C6H5)] (3), whereby usage of a diboron B2pin2 promotes hydride elimination to form the salt [K(18-C-6)HB2Pin2] (4). Similarly, 3 can also be formed by cleavage of the C-F bond of fluorobenzene. Reaction of 3 with ClBcat yields [K(18-C-6)(thf)2][(tBupyrr2pyr)FeCl] (5) and PhBcat and the former can be reduced to 2 to complete a synthetic cycle for heterolytic benzene C-H activation and borylation.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Here we report the use of a base metal complex [( t Bu pyrpyrr 2 )Fe(OEt 2 )] ( 1 -OEt 2 ) ( t Bu pyrpyrr 2 2− =3,5- t Bu 2 -bis(pyrrolyl)pyridine) as a catalyst for intermolecular amination of C sp3 −H bonds of 9,10-dihydroanthracene ( 2 a ) using 2,4,6-trimethyl phenyl azide ( 3 a ) as the nitrene source. The reaction is complete within one hour at 80 °C using as low as 2 mol % 1 -OEt 2 with control in selectivity for single C−H amination versus double C−H amination. Catalytic C−H amination reactions can be extended to other substrates such as cyclohexadiene and xanthene derivatives and can tolerate a variety of aryl azides having methyl groups in both ortho positions. Under stoichiometric conditions the imido radical species [( t Bu pyrpyrr 2 )Fe{=N(2,6-Me 2 -4- t Bu-C 6 H 2 )] ( 1 -imido) can be isolated in 56 % yield, and spectroscopic, magnetometric, and computational studies confirmed it to be an S = 1 Fe IV complex. Complex 1 -imido reacts with 2 a to produce the ferrous aniline adduct [( t Bu pyrpyrr 2 )Fe{NH(2,6-Me 2 -4- t Bu-C 6 H 2 )(C 14 H 11 )}] ( 1 -aniline) in 45 % yield. Lastly, it was found that complexes 1 -imido and 1 -aniline are both competent intermediates in catalytic intermolecular C−H amination.