A Porphyrin Skeleton Containing a Palladacyclopentadiene

Chemistry inside a Porphyrin Skeleton: Platinacyclopentadiene from Tellurophene

“…The target molecule, 21-platina-23-telluraporphyrin has been obtained in ah eteroatom-replacementp rocedure. Such as ubstitution scheme provede ffective in our former studies:t he telluropheneu nit in an aromatic telluraporphyrin transformed into furan, [23] or a palladacyclopentadiene ring [17] in at ellurium atom exchange reaction, yielding oxa-andp alladaporphyrin, respectively.W e have chosen meso-tetraphenyl-21,23-ditelluraporphyrin, 4,for a reactive substrate. [24] Thus, 4 treated withP t(PhCN) 2 Cl 2 in boiling toluenei na naerobic conditions afforded ap latinum(II) complex, 5,10,15,20-tetraphenyl-21-platina-23-telluraporphyrin 5 (Scheme 2) in 30 %y ield.…”

“…[26,27] Typically,a na ngle between C-Te-C plane and PtÀTe bond for organotellurium platinum complexes is in range 1068-1138, [28] in special cases even lower (for ad itelluraisophlorin palladium complex, the analogousa ngle is 888 [29] ), while for presented platinatelluraporphyrins flattened by macrocycle constrains, it is significantly larger,r eaching 1328-1418 (Table S2), close to the corresponding angle in 21-pallada-23telluraporphyrin (1488). [17] Thus, the overall platinaporphyrins deformation is ar esultant of several antagonistic forces:t he tendency of platinum ions to square-planar or octahedral coordination geometry,t he tellurium donor coordination preferences, the size of core atoms, and finally,t he porphyrin skeleton constrains.…”

“…The product 2,formally avacataporphyrin(3)complex was up to now,e xemplified solely by 21-pallada-23-telluraporphyrin (2,M= Pd, X' = Te ). [17] At the same time, the metallacyclopentadienes tabilization in the aromatic environment of ap orphyrin, is relevantt om etallacycle chemistry,g aining interest in context of unconventional aromaticity,i ncluding Mçbiusa romaticity,a nd the question of metal orbitals participation in delocalization of electrons. [18][19][20] The related keyword meso-metallaporphyrin,d escribes ad ifferent typeo fm acrocycles, nonaromatic structures based on four 1,2,3-triazole rings fixed with four meso-metal ions, forming ap orphyrin-like geometry.…”

Expanded Porphyrin Contraction: From [22]Triphyrin(6.6.0) to [22]Triphyrin(6.5.0)

“…Thus, another approach, based on the post‐synthetic transformations of a macrocyclic skeleton may be more efficient and lead to structures difficult to obtain by assembly of small units . Skeletal rearrangements are encountered rather rarely; they may be exemplified by a core heteroatom replacement or extrusion, macrocyclic fusion, and ring expansion or contraction. For porphyrinoid aromatic macrocycles a contraction may take place at both—a meso ‐link or at a cyclic subunit, like a pyrrole in a regular porphyrin, a phenylene ring in benziporphyrin or naphthiporphyrin, or at the outer heptacyclic ring of azuliporphyrinoids as well .…”

“…[2,3] In fact, in the latter approach, the buildingb locks assemblyi sg overned by thermodynamic and kinetic factors and have been fruitful throughout the porphyrinoid chemistry.H owever,a ccessibilityo fd esired building blocks furnished with appropriate side groups capable of buildingc onnections with otheru nits may be low.T hus, another approach, based on the post-synthetic transformations of am acrocyclic skeletonm ay be more efficient and lead to structuresd ifficultt oo btain by assemblyo fs mall units. [4][5][6] Skeletal rearrangementsa re encountered rather rarely; they may be exemplified by ac ore heteroatom replacement [7] or extrusion, [8][9][10] macrocyclic fusion, [11,12] and ring expansion [6,13,14] or contraction.F or porphyrinoid aromatic macrocyclesacontraction may take place at both-a meso-link [6,[15][16][17][18][19] or at ac yclic subunit, like ap yrrole in ar egularp orphyrin, [20,21] ap henylene ring in benziporphyrin [22][23][24][25][26] or naphthiporphyrin, [27] or at the [a] Dr.E.…”