A new access route to dimetal sandwich complexes, including a radical anion†
The amide in Cr[N(SiMe3)2]2(THF)2 is displaced by equimolar [K(18-crown-6)][naphthalene] to form the dimetal sandwich Cr2(naphthalene)2− as a radical anion paired with [K(18-crown-6)]+. Two Cr atoms in the sandwich do not form any multiple Cr/Cr bonds, and instead each interacts with one naphthalene in an η6 fashion and with the second naphthalene in an η4 connectivity mode. The naphthalene C/C distances show the effect of back donation from two chromium atoms to a greater extent than simply by 1 electron ring reduction, in comparison to the naphthalene radical anion. The SOMO of the product was established by variable temperature EPR spectroscopy, and the atom ratios and elemental purity were supported by XPS. The possible generality of the displacement of N(SiMe3)2− from a low valent metal is discussed.