名称:
Divergent reactivity of [(κ3-L)ThCl2(dme)] with Grignard reagents: Alkylation, ancillary ligand transfer to magnesium, and halide exchange caught in the act
摘要:
Reaction of [(BDPP)ThCl2(dme)] (1) with 2 equivalents of MeMgBr in OEt2, followed by filtration and layering a toluene solution with hexanes at -30 degrees C yielded a single large crystal of [{(BDPP)ThX (mu-X)(2)Mg(OEt2)(mu-Me)}(2)]center dot 2 toluene (X = Br0.73-0.87/Cl0.13-0.27; 3 center dot 2 toluene). This product is the result of halide exchange to form a partially brominated neutral thorium species, which is adducted with MeMgX(OEt2). The complex is then tetrametallic as a result of Mg-Me-Mg bridges. The structure of complex 3 provides direct insight into the process by which halide exchange takes place between electrophilic metal halide complexes and Grignard reagents. This reactivity stands in stark contrast to the reactions of 1 and [(XA(2))ThCl2(dme)] (2) with PhCH2MgCl. In these cases the expected dialkyl products, [LTh(CH2Ph)(2)] [L = BDPP (4) and XA(2) (5)], were formed under most conditions. However, addition of a PhCH2MgCl solution to 2 at -78 degrees C and warming to room temperature after 5 minutes gave [(XA(2))Mg(dme)] (6), the product of ancillary ligand transfer from thorium to magnesium, in 30 -50% yield. (c) 2010 Elsevier B.V. All rights reserved.