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.
Tetraaryl‐21,23‐dirhodaporphyrin and a series of related monorhodaporphyrins have been obtained by tellurium‐to‐rhodium exchange in a reaction of tetraaryl‐21,23‐ditelluraporphyrin with [RhCl(CO)2]2. These organometallic metallaporphyrins contain rhodium(III) centers embedded in rhodacyclopentadiene rings, incorporated within the porphyrin frames. The skeletons of 21,23‐dirhodaporphyrin and 21‐rhoda‐23‐telluraporphyrin are strongly deformed in‐plane from the rectangular shape typical for porphyrins, due to rhodium(III) coordination preferences, the large size of the two core atoms, and the porphyrin skeleton constrains. These two metallaporphyrins exhibit fluxional behavior, as studied by 1H NMR and DFT, involving the in‐plane motion and the switch of the rhodium center(s) between two nitrogen donors. A side product detected in the reaction mixture, 21‐oxa‐23‐rhodaporphyrin, results from tellurium‐to‐oxygen exchange, occurring in parallel to the tellurium‐to‐rhodium exchange. The reaction paths and mechanisms have been analyzed. The title 21,23‐dirhodaporphyrin contains a bridged bimetallic unit, Rh2Cl2, in the center of the macrocycle, with two rhodium(III) ions lying approximately in the plane of the porphyrinoid skeleton. The geometry of the implanted Rh2Cl2 unit is affected by macrocyclic constrains.
Invited for the cover of this issue is the group of Ewa Pacholska‐Dudziak at the University of Wroclaw. The image depicts two rhodium atoms being fixed into the skeleton of 21,23‐dirhodaporphyrin in place of two core nitrogen donors. Read the full text of the article at 10.1002/chem.202201513.
Dwarfs are shown fixing two rhodium atoms into the skeleton of 21,23‐dirhodaporphyrin, the first [18]porphyrin to incorporate two metal atoms within its macrocyclic frame, in place of two core nitrogen donors. The 18‐π‐electron aromatic circuit is maintained, playing a crucial role in stabilizing the macrocycle, and enforcing the metal centers′ proximity. These small metal sculptures of dwarfs are a tourist attraction scattered around Wrocław, the city in Poland where the dirhodaporphyrin was synthesized. More information can be found in the Research Article by E. Pacholska‐Dudziak and co‐workers (DOI: 10.1002/chem.202201513).
Ditelluraporphodimethene, a nonaromatic porphyrinoid containing two tellurophene rings, reacted with palladium(II), platinum(II), and rhodium(I) following two different paths. Palladium(II) formed bonds to two tellurium donors of the macrocycle, yielding a side-on coordination compound, with a square planar (Te 2 Cl 2 ) metal ion environment. An alternative reaction path has been observed for ditelluraporphodimethene with platinum(II) or rhodium(I) in high boiling solvents. These conditions led to the profound transformation, that is, one tellurium atom to a metal atom exchange, resulting in the formation of organometallic species containing metallacyclopentadiene rings, that is, 21-platina-23-telluraporphodimethene and 21-rhoda-23-telluraporphodimethene. The substitution reaction proceeded selectively at the tellurophene ring within the conjugated part of the molecule, that is, the tellurophene ring bound to two sp 2 meso-carbon atoms. In the case of platinum, the exchange was accompanied by one meso-aryl ring fusion with the formed platinacyclopentadiene ring, and the platinum(II) macrocycle underwent reversible oxidation with chlorine. The products are stable and represent first nonaromatic examples of metalloporphyrinoids, with a metallacyclopentadiene ring incorporated into a porphodimethene skeleton.
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