Inverted-sandwich Dichromium(I) complexes supported by two β-diketiminates:: A multielectron reductant and syntheses of chromium dioxo and imido

Treatment of [Cr(mu-Cl)(Nacnac)](2) (Nacnac = HC(C(Me)NC6H3-i-Pr-2)(2)) with 2.5 equiv of KC8 in toluene allows the isolation of an inverted-sandwich toluene-bridged complex, (mu-eta(6):eta(6)-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 O-2, 4 equiv of MesN(3) (Mes = 2,4,6-C6H2Me3), and Ph2N2 engenders the formation of a monomeric Cr(O)(2)(Nacnac) (2), Cr(NMes)(2)(Nacnac) (3), and (mu-NPh)(Nacnac)](2) (4), respectively. Complex 1 is therefore an 8-electron reductant.