Dipyrromethene ligand scaffolds were synthesized bearing large aryl (2,4,6-Ph3C6H2, abbreviated Ar) or alkyl (tBu, adamantyl) flanking groups to afford three new disubstituted ligands (RL, 1,9-R2-5-mesityldipyrromethene, R = aryl, alkyl) While high-spin (S = 2), four-coordinate iron complexes of the type (RL)FeCl(solv) were obtained with the alkyl-substituted ligand varieties (for R = tBu, Ad and solv = THF, OEt2), use of the sterically encumbered aryl-substituted ligand precluded binding of solvent and cleanly afforded a high-spin (S = 2), three-coordinate complex of the type (ArL)FeCl Reaction of (AdL)FeCl(OEt2) with alkyl azides resulted in the catalytic amination of C−H bonds or olefin aziridination at room temperature Using a 5% catalyst loading, 12 turnovers were obtained for the amination of toluene as a substrate, while greater than 85% of alkyl azide was converted to the corresponding aziridine employing styrene as a substrate A primary kinetic isotope effect of 128(5) was obtained for the r

Catalytic C-H bond amination from high-spin iron imido complexes.

The clusters of nitrogenase: synthetic methodology in the construction of weak-field clusters.

Compounds that contain a late transition metal-nitrogen multiple bond represent important reactive intermediate species in many useful organic and inorganic transformations. In order to understand the role that these intermediates play in reactions, it is important to have a full understanding of their electronic structure. This paper reviews the known structural motifs that occur in late transition metal nitrido and imido compounds, and provides a correlation between geometric structure and electronic structure. Also, intermediate species that have been postulated but not yet isolated are discussed, as these compounds represent exciting targets for further efforts in synthetic inorganic chemistry.

Terminal nitrido and imido complexes of the late transition metals

Adaptable metallaboratranes: A tris- (phosphino)borane ligand stabilizes both low-valent Fe-N_2 complexes and a mid-valent imido species with a Fe≡NAr bond, thanks to its ability to shuttle between trigonal-bipyramidal and pseudotetrahedral geometries by elongation of the apical iron–boron bond (see picture)

Terminal iron dinitrogen and iron imide complexes supported by a tris(phosphino)borane ligand.

Entry into “[PhBP3]Fe” chemistry affords a rare, pseudotetrahedral iron(I) complex, [PhBP3]Fe(PPh3), with an S = 3/2 ground state. This precursor undergoes rapid oxidation by aryl azide to produce the d5 imide [PhBP3]Fe⋮NAr (Ar = p-tolyl). The Fe(III) imide is significant in that it is low-spin and represents the first mononuclear imide of iron. Doublet [PhBP3]Fe⋮NAr reacts rapidly and quantitatively with CO at room temperature to release isocyanate and [PhBP3]Fe(CO)2. The [PhBP3]Fe(CO)2 byproduct is also a precursor to [PhBP3]Fe⋮NAr upon addition of aryl azide.

and Catalina Achim

Papers

A Stable Terminal Imide on Iron