Abstract
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. © 2011 The Royal Society of Chemistry.