Isomerization by ligand shuffling along a Cr24+ unit: further reactions leading to cleavage of a quadruple bond

The paddlewheel complex Cr2(DpyF)4(1), where DpyF =N,N-di(2-pyridyl)formamidinate, has a short Cr(identical)Cr distance of 1.938(2) (angstrom)for the CrCr quadruple bond. In solution, there is a series of interconverting isomers, as determined by variable temperature 1H NMR studies. Compound 1 can be readily oxidized by CuCl2 to produce [Cr2(DpyF)4][CuCl2]2(2) and [Cr2(DpyF)4CuCl3][CuCl2](3). In both cases, the metal-metal quadruple bond is cleaved in favor of six-coordinate Cr(III) ions. Magnetic measurements for the oxidized products show that the chromium ions in the dichromium units exhibit strong antiferromagnetic interactions.