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

A novel Tp^Me2-supported (Tp^Me2 = 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 Tp^Me2LnCl₂ with 2 equiv of K­[(RN)₂CN­(SiMe₃)₂] (KGua) gave the methylamidinate complexes Tp^Me2Ln­[(RN)₂CMe]­[N­(SiMe₃)₂] (R = isopropyl, Ln = Y (<b>1</b>^<b>Y</b>), Er (<b>1</b>^<b>Er</b>); R = cyclohexyl, Ln = Y (<b>2</b>^<b>Y</b>)) in moderate yields. In contrast, Tp^Me2YCl₂(THF) reacted with 1 equiv of KGua to afford a C–N cleavage product Tp^Me2Y­(Cl)­N­(SiMe₃)₂(THF) (<b>4</b>), indicating that this guanidinate ligand is not stable in the yttrium complex with the Tp^Me2 ligand, and a carbodiimide deinsertion takes place easily. The mechanism for the formation of complexes <b>1</b> and <b>2</b> 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