A series of iron complexes featuring the pyridine dipyrrolide (PDP) pincer ligand [Cl2PhPDPPh]2−, obtained via deprotonation of 2,6‐bis(5‐(2,6‐dichlorophenyl)‐3‐phenyl‐1H‐pyrrol‐2‐yl)pyridine, H2Cl2PhPDPPh, is reported and structurally and spectroscopically characterized. While the bis‐pyridine adduct (Cl2PhPDPPh)Fe(py)2 exhibits nearly identical features as previously reported (MesPDPPh)Fe(py)2 (H2MesPDPPh=2,6‐bis(5‐(2,4,6‐trimethylphenyl)‐3‐phenyl‐1H‐pyrrol‐2‐yl)pyridine), the diethyl ether and tetrahydrofuran adducts (Cl2PhPDPPh)Fe(OEt2) and (Cl2PhPDPPh)Fe(thf) show additional weak Fe−Cl interactions that impact the overall coordination geometries and result in strong deviations from planar coordination environments. The reaction of (Cl2PhPDPPh)Fe(thf) with 1‐adamantyl azide provided the isolable iron imido complex (Cl2PhPDPPh)Fe(N1Ad), highlighting the improved stability of [Cl2PhPDPPh]2− towards intramolecular nitrene group transfer from the high‐valent iron‐imido unit. The electronic structure of (Cl2PhPDPPh)Fe(N1Ad) was investigated by density functional theory (DFT) and complete active space self‐consistent field (CASSCF) calculations. These computational studies suggest energetically close‐lying diamagnetic and paramagnetic states and help to conceptualize the unusual magnetic properties of the complex observed by variable‐temperature 1H NMR spectroscopy.

The photoluminescent eight-coordinate zirconium complex Zr(HPMPH)4 supported by four monoanionic 2-(2’-pyridine)pyrrolide ligands was synthesized. This molecule shows dual emission via fluorescence and phosphorescence with an overall quantum efficiency of 4%...

The reaction between the square-planar, paramagnetic iron−carbene complex ( Mes PDP Ph )Fe(CPh 2 ) (where [ Mes PDP Ph ] 2− is the doubly deprotonated form of 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1H-pyrrol-2-yl)pyridine) and two equivalents of carbon monoxide or 2,6-dimethylphenylisocyanide, CNdmp, resulted in carbene insertion into a Fe−N pyrrole bond of the Mes PDP Ph ligand. Crystallographic studies established complete scission of the Fe−N pyrrole bond in the resulting low-spin Fe II complexes. Experiments using 1-adamantylisocyanide, CN 1 Ad, demonstrated that binding of two exogenous ligands was required to promote carbene migration and allowed the isolation of diamagnetic ( Mes PDP Ph )Fe(CPh 2 )(CN 1 Ad). Computational studies by density functional theory (DFT) and complete-active-space self-consistent field (CASSCF) calculations support that ( Mes PDP Ph )Fe(CPh 2 )(CN 1 Ad) possesses a similar electronic structure to porphyrin iron carbenes, best described as containing a neutral Fischer-type carbene coordinated to a low-spin Fe II center. DFT calculations also suggested that carbene migration is triggered by an increase in carbene electrophilicity upon binding of a second isocyanide ligand. Thermolysis of the carbene insertion product obtained following the addition of CNdmp to ( Mes PDP Ph )Fe(CPh 2 ) revealed that the insertion is fully reversible and provided the ketenimine N-(2,2-diphenylethenylidene)-2,6-dimethylbenzenamine as the major product.

Abstract2,6‐Bis(pyrrol‐2‐yl)pyridines are important building blocks for supramolecular assemblies and photoluminescent main group and transition metal compounds. Sterically encumbered 2,6‐bis(5‐(2,4,6‐trimethylphenyl)‐3‐phenyl‐1H‐pyrrol‐2‐yl)pyridine, H2MesPDPPh, can adopt monomeric and dimeric structures in the solid state and in solution, controlled by competing inter‐ and intramolecular hydrogen bonds. Deprotonation in the presence of lithium cations provides Li2MesPDPPh, which can be isolated in monomeric and dimeric forms depending on solvent polarity. Protonation of H2MesPDPPh disrupts intramolecular hydrogen bonding and provides the monomeric pyridinium salt [H3MesPDPPh]Cl. Independent of solvent polarity, all three derivatives exhibit intense fluorescence in solution. The absorption and emission spectra are highly sensitive to the level of protonation, which can be rationalized by the effects of (de)protonation on the HOMO and LUMO of the tricyclic π‐system.