Inverted-Sandwich Dichromium(I) Complexes Supported by Two β-Diketiminates: A Multielectron Reductant and Syntheses of Chromium Dioxo and Imido

Abstract

Treatment of [Cr(μ-Cl)(Nacnac)]2 (Nacnac = HC(C(Me)NC6H3-i-Pr2)2) with 2.5 equiv of KC8 in toluene allows the isolation of an inverted-sandwich toluene-bridged complex, (μ-η6:η6-C7H8)[Cr(Nacnac)]2 (1), in 88.2% yield as a dark-purple solid. The valency of each Cr is determined to be I by X-ray absorption spectroscopy. The twelve Cr−C distances are moderately long and 1 readily undergoes an arene exchange reaction with benzene. As a result, 1 behaves as a two-Cr(Nacnac) synthetic equivalents upon reaction with appropriate substrates. For example, treatment of 1 with 2 equiv of O2, 4 equiv of MesN3 (Mes = 2,4,6-C6H2Me3), and Ph2N2 engenders the formation of a monomeric Cr(O)2(Nacnac) (2), Cr(NMes)2(Nacnac) (3), and (μ-NPh)(Nacnac)]2 (4), respectively. Complex 1 is therefore an 8-electron reductant.