Syntheses and solid-state structures of two cofacial (bis)dipyrrin dichromium complexes in different charge states.

The dichromium Pacman complex (tBudmx)Cr2Cl2·C4H10O (1) [(tBudmx)H2 is a dimethylxanthene-bridged cofacial (bis)dipyrrin, C49H58N4O] was synthesized by salt metathesis using anhydrous CrCl2 and previously reported (tBudmx)K2. Treatment of 1 with two equivalents of the reductant potassium graphite afforded K2(tBudmx)Cr2Cl2(thf)3·0.5C4H10O·0.5C4H8O (thf is tetrahydrofuran, C4H8O) (2), with both potassium ions intercalated between the pyrrolic subunits. Comparison of the solid-state structures for 1 and 2 reveals minimal changes in the primary coordination sphere of each Cr ion, with notable elongation of the dipyrrin C-C and C-N bonds upon reduction, consistent with computational support for a ligand-based reduction.