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).
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