Synthesis and Structure of Silicon-Bridged Boratabenzene Fluorenyl Rare-Earth Metal Complexes

A silicon-bridged boratabenzene fluorenyl ligand [Me2Si­(C13H8)­(C5H4BNEt2)]2– (L2–) was designed and synthesized. By employment of this ligand, two divalent rare-earth metal complexes [Me2Si­(C13H8)­(C5H4BNEt2)]­Ln­(THF)2 (Ln = Sm (1), Yb (2)) were obtained from salt metathesis of K2[Me2Si­(C13H8)­(C5H4BNEt2)] (K2L) with LnI2­(THF)2 in THF. Complex 2 undergoes redox reaction with cyclooctatetraene to give a trivalent Yb complex [(C8H8)­Yb]2­[μ-{Me2Si­(C13H8)­(C5H4BNEt2)}2] (3), accompanied with oxidative coupling of two fluorenyl groups. A series of chloro-bridged trimeric trivalent rare-earth metal complexes [Li­(THF)4]2­[{[Me2Si­(C13H8)­(C5H4BNEt2)]­Ln­(μ-Cl)­Li­(THF)3}3­(μ-Cl)3­(μ3-Cl)2] (Ln = Nd (4), Sm (5), and Gd (6)) were synthesized by reactions of Li2[Me2Si­(C13H8)­(C5H4BNEt2)] (Li2L) with LnCl3 in THF. Treatment of K2[Me2Si­(C13H8)­(C5H4BNEt2)] (K2L) with LnI3(THF)n gave the monomeric complexes [Me2Si­(C13H8)­(C5H4BNEt2)]­LnI­(THF) (Ln = La (7), Nd (8), Sm (9), and Gd (10)). These iodides were subsequently reacted with K­[CH2C6H4-o-NMe2] to afford THF coordinated benzyl complexes [Me2Si­(C13H8)­(C5H4BNEt2)]­Ln­(CH2C6H4-o-NMe2)­(THF) (Ln = La (11), Nd (12), and Gd (13a)) and non-THF coordinated complex [Me2Si­(C13H8)­(C5H4BNEt2)]­Gd­(CH2C6H4-o-NMe2) (13b).