Rhenium Biscorrole Sandwich Compounds: XAS Evidence for A New Coordination Motif

Interaction of three free-base meso-tris(p-X-phenyl)corroles H3[TpXPC] (X = H, CH3, OCH3) with Re2(CO)10 at 235 C in the presence of K2CO3 in o-dichlorobenzene has led to putative rhenium biscorrole sandwich compounds with the formula ReH[TpXPC]2. DFT calculations and Re L3 EXAFS measurements suggest a seven-coordinate metal center, with the extra hydrogen located on one of the corrole nitrogens. The complexes can be deprotonated by a base such as DBU, resulting in substantial sharpening of UV-visible spectra and split Soret bands, consistent with the generation of C2-symmetric anions. Both the seven-coordinate neutral and the eight-coordinate anionic forms of the complexes represent a new coordination motif in the field of Re-porphyrinoid interactions.