Me–Si Bond Cleavage of Anionic Bis(trimethylsilyl)amide in Scorpionate-Anchored Rare Earth Metal Complexes

A novel TpMe2-supported (TpMe2 =
tri­(3,5-dimethylpyrazolyl)­borate) rare earth metal complex promoted
Me–Si cleavage of the bis­(trimethylsilyl) amide ligand ([(Me3Si)2N]−) was observed. Reaction
of TpMe2LnCl2 with 2 equiv of K­[(RN)2CN­(SiMe3)2] (KGua) gave the methylamidinate
complexes TpMe2Ln­[(RN)2CMe]­[N­(SiMe3)2] (R = isopropyl, Ln = Y (1Y), Er (1Er); R = cyclohexyl,
Ln = Y (2Y)) in moderate yields.
In contrast, TpMe2YCl2(THF) reacted with 1 equiv
of KGua to afford a C–N cleavage product TpMe2Y­(Cl)­N­(SiMe3)2(THF) (4), indicating that this
guanidinate ligand is not stable in the yttrium complex with the TpMe2 ligand, and a carbodiimide deinsertion takes place easily.
The mechanism for the formation of complexes 1 and 2 was also studied by controlling the substrate stoichiometry
and the reaction sequence and revealed that the bis­(trimethylsilyl)­amine
anion N­(SiMe3)2– can undergo
two routes of γ-methyl deprotonation and Si–Me cleavage
for its functionalizations. All these new complexes were characterized
by elemental analysis and spectroscopic methods, and their solid-state
structures were also confirmed by single-crystal X-ray diffraction.