Rhodium Complexes of a New‐Generation Sapphyrin: Unique Structures, Axial Chirality, and Catalysis

Abstract

Rhodium insertion into the new 5,10,15,20-tetrakis(trifluoromethyl)sapphyrin was found to be much more facile than for other analogues, owing to NH⋅⋅⋅F hydrogen-bonding interactions that stabilise the pyrrole-inverted structure characteristic of the metallated product. The thus-obtained rhodium(I) complexes have axial chirality, and the enantiomers were resolved. The latter were found to interconvert quite rapidly in a process that involves a tautomerisation-like movement of the metal fragment between the five N atoms. The rhodium sapphyrins were investigated as catalysts for organic synthesis, by studying their carbene-transfer activity in the cyclopropanation of styrene with ethyl diazoacetate and comparing it to that of rhodium corroles.

Resolution of Expanded Porphyrinoids: A Path to Persistent Chirality and Appealing Chiroptical Properties

“…In 2018, the Gross group reported the synthesis of a new sapphyrin, namely 5,10,15,20‐tetrakis(trifluoromethyl)sapphyrin 13 (Scheme 1). [10c] Insertion of a single rhodium(I) ion was found to yield a C 1 symmetric complex 13‐Rh with axial chirality. A single crystal X‐ray diffraction structural analysis of 13‐Rh revealed the presence of two enantiomers in the solid state in the expected 1 : 1 ratio.…”

“…This can be particularly apparent in the case of expanded porphyrinoids complexed with transition metals. The latter are of interest as potential catalysts in asymmetric synthesis [10] and as possible mimics for naturally occurring topologically chiral systems, such as the right-handed α-helix in proteins and the double-stranded helix seen in canonical forms of DNA. [11] Furthermore, these conformationally locked expanded porphyrinoids represent promising functional materials that possess unique chiroptical properties as reflected in their circular dichroism (CD) and circularly polarized luminescence (CPL) spectra.…”

Rh(I) Complexes in Catalysis: A Five-Year Trend

“…To conclude this survey on the last five-year trends in the synthesis of Rh(I) complexes for catalytic applications, some interesting "exotic" structures that can be used as ligands for these coordination compounds should be cited, such as the sapphyrin or corrole derivatives and the substituted carboranes. In the first case, five new rhodium chelated complexes containing sapphyrins and corroles bearing fluorinated alkyl or aryl groups (C 6 F 5 or CF 3 ) on their meso-C atoms were prepared and characterized [84] (Figure 6), and their rich coordination chemistry was studied to understand the structural and electronic properties of these compounds, including elements of chirality. All the sapphyrine derivatives had one inverted pyrrole ring, and the crystal structure evidenced their C 1 -symmetric nature, leading to the corresponding enantiomers in a 1:1 ratio.…”

Kinetic trapping of a cobalt(ii) metallocage using a carbazole-containing expanded carbaporphyrinoid ligand

“…[4][5][6] In addition, expanded porphyrins have been used for metal ion recognition and sensing; [7][8][9][10][11] they have also been incorporated into stimuli responsive molecular machines. 12 Other metallated expanded porphyrins have been investigated as catalysts for organic synthesis 13,14 and as functional photoacoustic imaging agents. 15 In 2014, Lash and coworkers described a so-called adjdicarbaporphyrin that stabilises an unusual tris-palladium sandwich complex.…”