Chemistry inside a Porphyrin Skeleton: Platinacyclopentadiene from Tellurophene

Abstract

Platinum(II) binds to 21,23-ditelluraporphyrinforming as ide-on complex,w hich can be easily transformed into an aromatic metallaporphyrin,t hat is, 21-platina-23-telluraporphyrin, with ap latinacyclopentadiene unit built in the porphyrin skeleton in place of one pyrrole ring. The central platinum(II) ion with aC CNTes quare-planarc oordination sphere can be oxidized to platinum(IV) by chlorine, bromine, methyl iodideora llyl chloridet oy ield octahedral complexes. All platinatelluraporphyrins show dynamic behaviori nvolving the platinum ion coordination sphere fluxionality and the porphyrin skeleton deformation, both in-plane and outof-plane, as demonstrated by 1 HNMR spectroscopy.

Two Rhodium(III) Ions Confined in a [18]Porphyrin Frame: 5,10,15,20‐Tetraaryl‐21,23‐Dirhodaporphyrin

“…Macrocycle 2 (11 to 30 % yield, depending on aryl substituents) with octahedral central ion coordinating two axial ligands: carbonyl and chloride anion, resembles known 21-platina-23-telluraporphyrins containing platinum(IV). [20] The macrocycle 2-H, closely related to 2, was isolated from the reaction mixture in low yield (0.7-3 % yield), but can be easily obtained from 2 by treatment with hydrogen chloride. The transformation 2!2-H leads to protonation of a nitrogen atom accompanied by one axial ligand exchange, that is, neutral carbonyl to anionic chloride.…”

“…The tellurophene ring inclination reflects the propensity of organotellurium ligands for a side-on coordination, [28] and similar distortion has been previously reported for 21-platina-23-telluraporphyrins. [20] The nonplanarity of 21-rhoda-23-telluraporphyrins is strongly influenced by nitrogen-24 protonation (Figure S50). Whereas N24 in 2 is oriented towards tellurium atom and not much tilted, in 2-H the NH group is pointing to an axial chloride and this pyrrole ring is significantly leaned out of porphyrin C 4-meso plane (24°).…”

“…The described tellurium to rhodium exchange proceeds more easily than analogous tellurium to palladium and tellurium to platinum substitutions. [19,20] The transformation of 1 into 2 proceeds readily at room temperature, while direct syntheses of palladium and platinum analogs required heating to 40 °C and 110 °C respectively. High reactivity of telluraporphyrins towards rhodium(I) is also reflected by feasibility of both tellurium atoms replacement leading to formation of 3.…”

“…This class of stable, aromatic, organometallic macrocycles was limited to 21-metalla-23-telluraporphyrins, containing one transition metal ion, palladium(II), [19] platinum(II) or platinum(IV). [20]…”

Telluracarbaporphyrins and a Related Palladium(II) Complex: Evidence for Hypervalent Interactions

“… Ditelluraporphyrins have unique properties, and the presence of two tellurophenes within the porphyrinoid framework results in one of the rings becoming inverted, although the inverted ring is strongly pivoted away from the macrocyclic plane. Treatment of 4 with hydrochloric acid afforded vacataporphyrin 7 , and ditelluraporphyrins were used to prepare dideazaaporphyrins (divacataporphyrins). , Ditelluraporphyrins have also been used to generate metallaporphyrins such as 8a , b . Recently, investigations into telluraporphyrin-type structures have attracted renewed interest and new examples have been reported, including tellurabenziporphyrins and ditelluradiazuliporphyrins …”