Bromobenzene Transforms Lanthanoid Pseudo-Grignard Chemistry

Abstract

Divalent lanthanoid pseudo-Grignard reagents PhLnBr (Ln=Sm, Eu and Yb) can be easily prepared by the oxidative addition of bromobenzene (PhBr) to lanthanoid metals in tetrahydrofuran (THF). PhLnBr reacts with bulky N,N′-bis(2,6-di-isopropylphenyl)formamidine (DippFormH) to generate LnII complexes, namely [Ln(DippForm)Br(thf)3]2⋅6thf (1; Sm, 2; Eu), and [Yb(DippForm)Br(thf)2]2⋅2thf (3; Yb). Samarium and europium (in 1 and 2) are seven coordinate, whereas ytterbium (in 3) is six coordinate, and all are bromine-bridged dimers. When PhLnBr reacts with 3,5-diphenylpyrazole (Ph2pzH), both divalent (5; [Eu(Ph2pz)2(thf)4]) and trivalent (4 a; [Sm(Ph2pz)3(thf)3]⋅3thf, 4 b; [Sm(Ph2pz)3(dme)2]⋅dme) complexes are obtained. In the monomeric compounds 4(a,b), samarium is nine coordinate but europium is eight coordinate in 5. The use of PhLnBr in this work transforms the outcomes from earlier reactions of PhLnI.