Bimolecular extrusion of TeR2 from beta-diketiminato supported scandium bis-tellurolates

Reaction of the well-defined, base-free dialkyl scandium compounds (LSc)-Sc -pi(CH2SiMe3)(2) supported by the beta -diketiminato ligands ArNC(R)CHC(R)N Ar (Ar = 2,6-diisopropyl; R = Me, L-1; R = tBu, L-2) with two equivalents o f nBu(3)P=Te gives the bis-tellurolate complexes (LSc)-Sc-pi(TeCH2SiMe3)(2) , 1b (L-1) and 2b (L-2). Tellurolate 2b was isolated and fully characterize d, including an X-ray structure analysis and exhibits two chemically distin ct tellurolate ligands in solution on the NMR time scale. Tellurolate 1b is only moderately stable and decomposes with elimination of two equivalents of Te(CH2SiMe3)(2) to form the dimeric bis-telluride Id. This compound was characterized by X-ray crystallography and elemental analysis. In contast, tellurolate 2b decomposes with loss of only one equivalent of Te(CH2SiMe3)( 2), leading to the formation of a dinuclear complex with one bridging tellu ride unit joining two (LSc)-Sc-2(TeCH2SiMe3) fragments. This compound was a lso structurally characterized. The solution behavior of this material is c omplex, as it exists as three conformational isomers that undergo slow exch ange on the NMR time scare. The production of dimer 2c, along with the resu lts of crossover experiments, suggest strongly that TeR2 elimination from t hese bistellurolates is bimolecular.