Mono- and Diboron Corroles: Factors Controlling Stoichiometry and Hydrolytic Reactivity

Abstract

The first example of a diboryl corrole complex, [(BF2)2(Br8T(4-F-P)C)](-) (Br8T(4-F-P)C = trianion of 2,3,7,8,12,13,17,18-octabromo-5,10,15-tris(4-fluorophenyl)corrole), has been isolated using the strongly electron-withdrawing and sterically crowded triaryl octabromocorrole ligand. Density functional theory (DFT) calculations show that the hydrolysis reaction producing the partially hydrolyzed complexes [B2OF2(Cor)](-) is more favored for the less sterically crowded triaryl corrole complexes. Monoboryl complexes BF2(H2Cor) (Cor = trianions of 5,10,15-triphenylcorrole (TPC), 5,10,15-tris(4-methylphenyl)corrole (T(4-CH3-P)C), 5,10,15-tris(4-trifluoromethylphenyl)corrole (T(4-CF3-P)C), and 5,10,15-tris(pentafluorophenyl)corrole (TPFPC)) were prepared and characterized. The experimental data are consistent with an out-of-plane dipyrrin coordination mode for these complexes, and DFT optimizations suggest that internal BF···HN hydrogen bonding may be significant in stabilizing these complexes. Further examples of the anionic diboron corrole [B2OF2(Cor)](-) containing the electron-withdrawing 5,10,15-tris(pentafluorophenyl)corrole (TPFPC) and the sterically hindered 10-(4-methoxyphenyl)-5,15-dimesitylcorrole (Mes2(4-MeOP)C) trianions are reported.

A new fundamental type of conformational isomerism

“…The porphyrin macrocycle provides a very versatile scaffold, exploited by Nature and chemists alike, chiefly due to its capacity to coordinate many elements in its central cavity. Brothers et al have developed the somewhat unusual class of porphyrin and related macrocycle derivatives featuring two inner coordinated boron atoms [46][47][48][49][50][51][52][53][54][55][56] in a 1,3-difluoro-1λ 4 ,3λ 4 -diboroxan-1,1,3,3-tetrayl group, abbreviated (BF)O(BF), that in porphyrins has each boron bonded in a transoid fashion to two adjacent pyrrolic nitrogen atoms. This, in principle, facilitates an encapsulated B−O−B linkage that could lead to isolable akamptisomers.…”

Multi‐Cation Coordination in Porphyrinoids

“…The F‐B‐ O ‐B‐F group occupies one face of the corrole in a cisoid arrangement ( 51 ), in contrast to the corresponding porphyrin complexes B 2 OF 2 (Por), which adopt an asymmetric transoid geometry ( 50 ) where one boron sits out of plane of the N4 core and one boron sits within the plane. The NMR spectra and X‐ray crystal structures of [B 2 OF 2 (Cor)] − confirm that the two boron atoms prefer the dipyrromethene sites and DFT calculations proved that the cisoid dipyrromethene isomer is the most stable …”

“…[2] Different structures of diboron porphyrinate and corrolatew ere synthesized using boron trihalides as reagents.T he reactions of BF 3 ·Et 2 Ow ith H 3 (Cor) and H 2 (Por) both produce complexes containing an F-B-O-B-F moiety,[ B 2 OF 2 (Cor)] À and [B 2 OF 2 (Por)] although with different stereochemistry.T he F-B-O-B-F group occupies one face of the corrolei nacisoid arrangement (51), in contrastt ot he corresponding porphyrin complexes B 2 OF 2 (Por), which adopt an asymmetric transoid geometry (50) where one boron sits out of plane of the N4 core and one boron sits within the plane.T he NMR spectra and X-ray crystal structureso f[ B 2 OF 2 (Cor)] À confirm that the two boron atoms prefer the dipyrromethene sites and DFT calculations proved that the cisoid dipyrromethene isomer is the most stable. [2,29] Interesting chemical properties were noticed for BF 2 - [22]and [20]smaragdyrins 54 and 55 respectively.B oth complexes are interchangeable via ar edox process (Scheme 13) switching their character from the Hückel aromatic to antiaromatic character according to the magnetic criterion. [18] At reatment of aromatic 54 and antiaromatic 55 with CuCl 2 in the presence of NaOAc gave hetero bimetal BF 2 - [20]smaragdyrin Cu II complex 56 in high yields, suggesting the facile oxidation of [22]smaragdyrin under these conditions.…”

Synthesis and molecular structure of perhalogenated rhenium-oxo corroles

“…Diboron corroles provide another example of a dramatic structural influence of β-octasubstitution. Thus, while simple corroles yield strongly domed complexes with cisoid FBOBF groups 71 , β-octabromo-meso-triarylcorroles yield unbridged bis-BF 2 complexes, with the BF 2 groups on opposite sides of corrole macrocycle 72 .…”