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.

Reduction of VCl(2)(Nacnac) (Nacnac = HC(C(Me)NC(6)H(3)-iPr(2))(2)) with KC(8) in toluene leads to the formation of a toluene-bridged inverted-sandwich divanadium(I) complex, (mu-eta(6):eta(6)-C(7)H(8))[V(Nacnac)](2), which behaves as a source of V(Nacnac) and a multi-electron reductant in the two reactions studied in this report.

Three dimeric vanadium(I) β-diketiminates [V{μ-(η(6)-ArN)C(Me)CHC(Me)C(N-Ar)}](2) (Ar = 2,6-Me(2)C(6)H(3) (2), 2,6-Et(2)C(6)H(3) (3), 9-anthracenyl (4)) were prepared and isolated upon reduction of their corresponding dichloro precursors VCl(2)(Nacnac). Compounds 2-4 all show a structure with each vanadium atom being η(2) bonded to the β-diketiminate framework and η(6) bonded to a flanking ring of a β-diketiminato ligand, attached to the other vanadium centre within the dimer. No metal-metal bonding interactions are observed in these dimers due to long vanadium-vanadium separations. Compounds 2-4 display an antiferromagnetic exchange between the two vanadium centres. An imido azabutadienyl complex (η(2)-PhCC(H)C(Ph)NC(6)H(3)-2,6-(i)Pr(2))VN(C(6)H(3)-2,6-(i)Pr(2))(OEt(2)) (5) was isolated from the reduction of VCl(2)(HC(C(Ph)NC(6)H(3)-2,6-(i)Pr(2))(2)) by KC(8). Compounds 2-4 and the inverted-sandwich divanadium complex (μ-η(6):η(6)-C(6)H(5)Me)[V(HC(C(Me)NC(6)H(3)-2,6-(i)Pr(2))(2))](2) (1) reduce Ph(2)S(2) to give two vanadium dithiolates V(SPh)(2)[(HC(C(Me)NC(6)H(3)-2,6-R(2))(2))] (R = Et (6), (i)Pr (7)) through an oxidative addition. Most notably, 1 and 3 catalyze the cyclotrimerization of alkynes, giving tri-substituted benzenes in good yields and a 1,3,5-triphenylbenzene coordinated intermediate 8 was isolated and characterized.

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