Cycloheptatrienyl dicarbollyl zirconium complexes: Building blocks for the preparation of multidecker sandwich complexes

The reaction of [(eta(7)-C7H7)ZrCl(tmeda)] (1, tmeda = N,N,N',N'-tetramethylethylene-1,2-diamine) with the sodium dicarbollide Na-2(C2B9H11) afforded the cycloheptatrienyl-dicarbollyl (Cht-Dcb) complex [Na(t-meda)][(eta(7)-Cht)Zr(eta(5)-Dcb)], [Na(tmeda)][2]. In the solid state, the sodium cations act as bridging units between the sandwich anions by eta(2)-and eta(3)-interaction with the Cht and Dcb ligands, respectively. The reaction of [Na(tmeda)][2] with BaI2 resulted in the formation of [Ba(thf)(5)(mu-eta(7):eta(7)-C7H7)Zr(eta(5)-C2B9H11)][(eta(7)-C7H7)Zr(eta(5)-C2B9H11)], [Ba(thf)(5)(2)][2], in which the cation exhibits an unusual bridging mu-eta(7):eta(7)-C7H7 unit between the Dcb-Zr and the Ba(thf)(5) fragments. An analogous reaction could not be effected by the salt metathesis reaction between [Na(tmeda)][2] and 0.25 equivalents of [(eta(5)-C5Me5)Ru(mu(3)-Cl)](4), since the ion pair [(eta(5)-C5Me5)Ru(tmeda)][2] containing the 16-electron half-sandwich tmeda complex was formed instead. The tetramethylammonium salt [NMe4][2] was prepared via an acid-base reaction between the amido complex [(eta(7)-C7H7)Zr{N(SiMe3)(2)}(thf)] and [NMe4][C2B9H12]center dot[NMe4][2] is more stable than its sodium congener [Na(tmeda)][2] and might therefore act as a suitable transfer reagent for the construction of multidecker sandwich transition metal complexes in the future (C) 2016 Elsevier B.V. All rights reserved.