Rhenium Biscorrole Sandwich Compounds: XAS Evidence for a New Coordination Motif.

The interaction of three free-base meso -tris( p -X-phenyl)corroles H 3 [T p XPC] (X = H, CH 3 , OCH 3 ) with Re 2 (CO) 10 at 235 °C in the presence of K 2 CO 3 in o -dichlorobenzene has led to putative rhenium biscorrole sandwich compounds with the formula ReH[T p XPC] 2 . Density functional theory calculations and Re L 3 -edge extended X-ray absorption fine structure 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 1,8-diazabicyclo[5.4.0]undec-7-ene, resulting in a substantial sharpening of the UV-vis spectra and split Soret bands, consistent with the generation of C 2 -symmetric anions. Both the seven-coordinate neutral and eight-coordinate anionic forms of the complexes represent a new coordination motif in the field of rhenium-porphyrinoid interactions.