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.

Rare‐Earth‐Metal Alkyl and Aryl Compounds in Organic Synthesis

“…More recently, Halim et al extended the Pseudo Grignard chemistry to bromide derivatives, utilizing in situ formed PhLnBr (2a Ln,Br ) instead of the iodide congener. [59] Accordingly, compounds 2a Ln,Br were treated with bulky HDippForm to afford the divalent complexes [Ln(DippForm)(μ-Br)(thf) x ] 2 (Ln = Sm, Eu, Yb). The crystal structures of the samarium and europium complexes revealed the coordination number 7 (x = 3), while the smaller ytterbium with CN = 6 accommodates only two THF molecules (x = 2) (cf.…”