Rhodium(III) Azuliporphyrins

Stateman, Leah M.; Ferrence, Gregory M.; Lash, Timothy D.

doi:10.1021/acs.organomet.5b00433

Cited by 26 publications

(32 citation statements)

References 55 publications

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“…Rhodium porphyrins have been used to selectively activate C–H and C–C bonds and can catalyze enantioselective cyclopropanation reactions . Rhodium(I) and rhodium(III) complexes of carbaporphyrins were only reported recently, although examples of rhodium N-confused porphyrins and azuliporphyrins had been described earlier. Reaction of carbaporphyrin 2 with di-μ-chlorotetracarbonyldirhodium(I) in refluxing dichloromethane afforded rhodium(I) complex 24 in up to 90% yield (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…Azuliporphyrins generally act as dianionic ligands, forming organometallic complexes with Ni(II), Pd(II), Pt(II), and Ru(II) . Rh(III) and Ir(III) azuliporphyrins have also been reported, , but these possess additional axial carbon ligands. Benziporphyrins are also dianionic ligands, whereas N-confused porphyrins can act as both dianionic or trianionic ligands .…”

Section: Introductionmentioning

confidence: 99%

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Metalation and Methyl Group Migration in 21-, 22-, and 23-Methylcarbaporphyrins: Synthesis and Characterization of Palladium(II), Rhodium(I), and Rhodium(III) Derivatives

2019

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A rational synthesis of 23-methylcarbaporphyrin has been developed. 3,4-Diethyl-1-methylpyrrole reacted with acetoxymethylpyrrole under acidic conditions to give N-methyltripyrrane, and following cleavage of the ester protective groups, the tripyrrolic intermediate condensed with an indene dialdehyde in the presence of trifluoroacetic acid to afford the required N-methylcarbaporphyrin. Reaction with palladium(II) acetate in refluxing acetonitrile for short time periods gave a 23-methyl palladium(II) complex but prolonged reaction times afforded a rearranged 21-methyl product. The 23methyl complex can be isolated but gradually converts into the 21-methyl derivative even in the solid state. 21-Methyl-and 22-methylcarbaporphyrins reacted with [Rh(CO) 2 Cl] 2 to give rhodium(I) complexes. However, when the 23-methylcarbaporphyrin was reacted under the same conditions, a rhodium-(III) derivative was isolated. This complex incorporates a bridging methylene unit between the Rh(III) and the 21-carbon and must therefore be formed by a methyl group migration−cyclization process.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metalation and Methyl Group Migration in 21-, 22-, and 23-Methylcarbaporphyrins: Synthesis and Characterization of Palladium(II), Rhodium(I), and Rhodium(III) Derivatives

2019

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“…Indeed, it is well-known that the conjugation pathways in porphyrinoid systems are often bifurcated and this factor makes it impossible to give these macrocycles a single structural representation. Azuliporphyrins have been shown to readily form organometallic derivatives AzP-M with Ni(II), , Pd(II), , Pt(II), Rh(III), Ir(III), and Ru(II) (Figure ). Furthermore, azuliporphyrins undergo oxidative ring contractions to give fully aromatic benzocarbaporphyrins 2 .…”

Section: Resultsmentioning

confidence: 99%

Tropylium and Porphyrinoid Character in Carbaporphyrinoid Systems. Relative Stability and Aromatic Characteristics of Azuliporphyrin and Tropiporphyrin Tautomers, Protonated Species, and Related Structures

AbuSalim

Lash

2018

J. Phys. Chem. A

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DFT studies have been carried out on 46 azuliporphyrin (AzP) and tropiporphyrin (TrP) tautomers, cations, and dications. The structures were minimized using DFT-B3LYP/6-311++G(d,p), and the relative stabilities of the tautomers for each series were computed with M06-2X and B3LYP-D3 functionals. Nucleus independent chemical shifts, both NICS(0) and NICS(1) zz , were calculated for both the center of the macrocycles and the individual pyrrolic and carbocyclic subunits. In addition, anisotropy of induced current density (AICD) plots were generated for all of the species under investigation. The results provided insights into the favored conjugation pathways and aromatic properties of these important carbaporphyrinoid systems. The π delocalization pathways for AzP were complex, and contrary to previous speculations, there was no evidence for tropylium characteristics in the favored free base structure. The global diatropicity of AzP was found to increase with increasing solvent polarity, in agreement with experimental observations. TrP was shown to be planar and to possess a large global diamagnetic ring current. However, NICS calculations and AICD plots indicated that the cycloheptatrienyl components of the two most favored TrP tautomers have paratropic characteristics. These results are not fully consistent with the proton NMR spectra for TrPs. A dihydroTrP and a Diels−Alder adduct were investigated, and these showed exceptionally large shielding effects with NICS(1) zz values of −36.53 and −36.92 ppm, respectively, in agreement with experimental results. A silver(III) complex of tropiporphyrin was also examined, and this showed no paratropic character for the seven-membered ring, although in this case, the system was found to be severely twisted. Overall, the results provide important information about the electronic properties of AzP and TrP tautomers, as well as for related protonated species, and complement the extensive experimental studies that have been conducted on these systems.

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“…Azuliporphyrins 9 are porphyrin analogues that have an azulene unit instead of one of the pyrrole rings (Figure ). This system acts as a dianionic ligand and affords organometallic derivatives with Ni(II), Pd(II), Pt(II), Ru(II), Rh(III), and Ir(III) . The first example of an azuliporphyrin was reported in 1997, and this system was shown to have significantly reduced diatropic properties compared to porphyrins or carbaporphyrins .…”

Section: Introductionmentioning

confidence: 99%

Azulichlorins and Benzocarbachlorins Derived Therefrom

2019

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Acid-catalyzed condensation of azulidipyrrane aldehydes with a dihydrodipyrrin carbaldehyde afforded the first examples of azulichlorins. These macrocyclic products were isolated in a monoprotonated form, and the free bases proved to be somewhat unstable. The monocations were strongly diatropic, and proton NMR spectroscopy showed the internal C−H at ca. −2 ppm. Addition of TFA gave the related dications, but these exhibited significantly reduced aromatic ring currents. Reaction of an azulichlorin with tert-butyl hydroperoxide and KOH in dichloromethane/methanol gave a benzocarbachlorin and two related aldehydes. The UV−vis spectrum for the benzocarbachlorin showed a split Soret band at 414 and 430 nm, together with a strong chlorinlike absorption at 684 nm. The proton NMR spectrum indicated that the carbachlorin is strongly aromatic and the internal C− H was observed at −4.64 ppm. Addition of TFA afforded a C-protonated dication with a significantly increased diatropic ring current. The proton NMR spectrum, NICS calculations, and AICD plots indicated that the system favors a 22π electron delocalization pathway that runs through the fused benzo unit. Addition of TFA to the benzocarbachlorin aldehydes primarily led to the formation of monocations, and the generation of C-protonated dications was no longer favored due to the presence of electron-withdrawing formyl moieties.

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Rhodium(III) Azuliporphyrins

Cited by 26 publications

References 55 publications

Metalation and Methyl Group Migration in 21-, 22-, and 23-Methylcarbaporphyrins: Synthesis and Characterization of Palladium(II), Rhodium(I), and Rhodium(III) Derivatives

Metalation and Methyl Group Migration in 21-, 22-, and 23-Methylcarbaporphyrins: Synthesis and Characterization of Palladium(II), Rhodium(I), and Rhodium(III) Derivatives

Tropylium and Porphyrinoid Character in Carbaporphyrinoid Systems. Relative Stability and Aromatic Characteristics of Azuliporphyrin and Tropiporphyrin Tautomers, Protonated Species, and Related Structures

Azulichlorins and Benzocarbachlorins Derived Therefrom

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