Journal Title: Inorganica Chimica Acta
Abstract: Herein we describe the synthesis, characterization, and role of three dichloric iron(III) complexes, [L1Fe(III)(Cl)2]ClO4 (L1Fe), [L2Fe(III)(Cl)2]ClO4 (L2Fe), and [L3Fe(III)(Cl)2]ClO4 (L3Fe) [L1 (Pyclen) = 1,4,7,10-tetra-aza-2,6-pyridinophane; L2 = 1,4,7,10-tetra-aza-2,6-pyridinophane-14-ol; L3 = 1,4,7,10-tetra-aza-2,6-pyridinophane-13-ol, in the coupling of pyrrole and phenylboronic acid to form 2-phenylpyrrole. The oxidation- and spin state of the iron complexes were characterized using X-ray crystallography, UV–vis absorbance spectroscopy, electron paramagnetic resonance spectroscopy, cyclic voltammetry, and mass spectrometry. Electrochemistry results rank ligand L1–L3 as moderate tetra-azamacrocycle donors to iron between cyclen and Me2EBC-12. Characterization of the iron(III) complexes and subsequent catalytic testing indicates that the complexes enter the C–C coupling catalytic cycle in the high-spin iron(III) oxidation state. Furthermore, the results indicate that the iron(III) complexes are essential for catalytic and regioselective production of the 2-phenylpyrrole product.
Author: Kayla Green, Associate Professor, Bio-inorganic Chemistry