N-Heterocyclic carbene bonding to cobalt porphyrin complexes

Molecular Systems Combining Porphyrinoids and N‐Heterocyclic Carbenes

“…Albrecht and co‐workers were the first to report axial coordination of NHCs to metalloporphyrins [19] . NHC cobalt complexes were relatively scarce at that time, because most of them are air and moisture sensitive and must be carefully handled under inert atmosphere to avoid unwanted redox processes.…”

“…Albrecht and co-workers were the first to report axial coordination of NHCs to metalloporphyrins. [19] NHC cobalt complexes were relatively scarce at that time, because most of them are air and moisture sensitive and must be carefully handled under inert atmosphere to avoid unwanted redox processes. For this reason, Albrecht's group used a porphyrin macrocycle as tetradentate ligand to stabilize the diamagnetic cobalt(III) cation and investigated axial ligation of imidazol-2-ylidenes on the resulting cobalt(III) porphyrin complexes.…”

Spectroscopic, Electrochemical, Magnetic and Structural Characterization of an Hexamethylenetetramine Co(II) Porphyrin Complex – Application in the Catalytic Degradation of Vat Yellow 1 dye

“…As mentioned above, cobaltous metalloporphyrins can exist, in non-aqueous solutions, as four-coordinated complexes type [Co II (Porph)], pentacoordinated species type [Co II (Porph)(L)] (L is a neutral axial ligand) and rarely as hexacoordinated derivative type [Co II (Porp)(L) 2 ]. It is worth noting that the UV-visible titrations of the starting material [Co II (Porph)] with numerous N-donor ligands such as pyridine and imidazole and their derivatives have been reported in the literature since the early seventies especially by Walker et al [5] and Yamamoto et al [51] . The titrations show that in major cases the 1:1 Co(II) porphyrin-L (L = N-bonded neutral ligand) species are forms [Eq.…”

Carbene-Type Species in the Functionalization of Porphyrin Derivatives

“…The synthetic strategy of the synthesis of 47 involved the decarboxylation of N,N′-dimethylimidazolium-2-carboxylate 46 in the presence of [Co(TPP)Cl]. 33 The exclusive formation of this highly stable complex 47, even in the presence of a large excess of 46, allowed the conclusion that the bonding to a second imidazole carbene is not favorable in contrast to the imidazole coordination behavior. The study showed that the chloride ligand in complex 47 can be readily abstracted by AgBF 4 affording complex 48 (Scheme 14); the latter successfully reacted with alcohols and imidazoles leading to complexes with octahedral geometry 49a,b and 50a,b, respectively.…”