Extrusion of Boron(III) Subporphyrin from meso‐Heptakis(pentafluorophenyl)[32]heptaphyrin upon Cooperative Cu^II and B^III Metalation

Abstract

An uneven split: Cooperative CuII and BIII metalation of meso‐heptakis(pentafluorophenyl)[32]heptaphyrin (1) triggers an extrusion reaction to produce BIII meso‐tris(pentafluorophenyl)[14]subporphyrin (2) along with a CuII porphyrin (3‐Cu). Subporphyrin 2 exhibits unique optical properties that reflect the rotational restriction of its electron‐withdrawing substituents.

Subporphyrins: A Legitimate Ring-Contracted Porphyrin with Versatile Electronic and Optical Properties

“…90 It has been thought that the transannular electronic interaction is enhanced at the hinge position of a figure-eight conformation of the octaphyrin upon the metalation. We have also demonstrated that the similar metathesislike splitting reactions of B(III)Cu(II) hybrid complexes of [32]heptaphyrins to B(III) [14]subporphyrin and Cu(II) [18]porphyrin, 91,92 the B(III) metalation-induced skeletal rearrangement from [28]hexaphyrin(1.1.1.1.1.1) to B(III) coordinated [28]hexaphyrin(2.1.1.0.1.1) via a transposition of a pentafluorophenyl-substituted meso-methine carbon, 93 Pd(II) metalation-induced formation of an N-confused porphyrin segment from [32]heptaphyrin substrates, 94 and Ni(II) metalation induced formation of a directly meso¢-linked diporphyrin. 95 The chemistry of expanded porphyrins have been reviewed elsewhere, 5255,96 where the emphasis was placed on the chemical reactivity and aromaticity.…”

“…In the solid state, 68 shows a twisted structure consisting of porphyrin-like unit and tripyrrolic segment with a pseudo C 2 -symmetry, where copper ion is bound to the porphyrinic segment in a squareplanar fashion. 91 In order to explore the possibility of ringsplitting reaction of heptaphyrins, B(III) complexation into the remaining tripyrrolic segments of 68 was attempted by treatment with boron trihalide under various conditions. Upon treatment with 100 equiv of BBr 3 in the presence of EtN(i-Pr) 2 at room temperature, the complex 68 disappeared readily to give a complicated mixture that included meso-pentafluorophenyl-substituted subporphyrin 71 and Cu(II) porphyrin 73 (Scheme 10).…”

“…Upon treatment with 100 equiv of BBr 3 in the presence of EtN(i-Pr) 2 at room temperature, the complex 68 disappeared readily to give a complicated mixture that included meso-pentafluorophenyl-substituted subporphyrin 71 and Cu(II) porphyrin 73 (Scheme 10). 66,91,164 The optimized yields were 36 and 13% yields for 71 and 73 respectively. The structure of subporphyrin 71 was determined by X-ray diffraction analysis to be a bowl shape (Figure 21).…”

Expanded Porphyrins: Intriguing Structures, Electronic Properties, and Reactivities

“…[83] Recently, octaphyrin mono-P V complex and bis-P V complex 107 were synthesized by using PCl 3 or POCl 3 as a phosphorylation reagent. Phosphorylation takes place initially to form a trigonal bipyramidal P V complex at the NCC site together with axial NN ligands and secondly at the remaining NNC site to form a phosphamide group (Figure 24).…”

meso-Trifluoromethyl-substituted Subporphyrin from Ring-splitting Reaction of meso-Trifluoromethyl-substituted [32]Heptaphyrin(1.1.1.1.1.1.1)

“…This idea came from recent findings that expanded porphyrins sometimes undergo unique skeletal rearrangements upon metallation or heating, 7,8 which are probably aided by transannular ³-electron interac- 2 to produce B(III) meso-pentafluorophenyl subporphyrin. 9 It was thus thought that similar subporphyrin-extrusion from meso-trifluoromethyl [32]heptaphyrin 5 may occur upon suitable metallation, since 5 is known to take a figure-eight conformation, 10 being suitable for the transannular interaction at the hinge-position.…”