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

Abstract

The paddlewheel complex Cr₂(DpyF)₄ (1), where DpyF = N,N′-di(2-pyridyl)formamidinate, has a short Cr–Cr distance of 1.938(2) Å 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.