Homoleptic Trigonal Planar Lanthanide Complexes Stabilized by Superbulky Silylamide Ligands

High Resolution Image Download MS PowerPoint Slide The lithium silylamides [Li(μ 3 -NHSiMe 2 Bu t )] 6 ( 1 ) and [Li(μ-NHSiPr i 3 )(THF)] 2 ( 2 ) were reacted with ClSiMe 3, ClSiMe 2 Bu t, or ClSiPr i 3 to prepare a series of secondary silylamines by salt metathesis reactions. These were deprotonated with KH to afford the group 1 transfer agents [K{μ-N(SiMe 2 Bu t )(SiMe 3 )}(C 7 H 8 )] 2 ( 3 ), [{K[μ-N(SiPr i 3 )(SiMe 3 )]} 2 ] ∞ ( 4 ), [{K[μ-N(SiMe 2 Bu t ) 2 ]} 2 (C 7 H 8 )] ∞ ( 5 ), [K{N(SiPr i 3 )(SiMe 2 Bu t )}] ∞ ( 6 ), [K{N(SiPr i 3 ) 2 }] ∞ ( 7 ), and [K{N(SiPr i 3 ) 2 }(THF) 3 ] ( 8 ). The synthetic utility of these group 1 transfer agents has been demonstrated by their reactions with [Ln(I) 3 (THF) 4 ] (Ln = La, Ce) in various stoichiometries to yield heteroleptic [La{N(SiMe 2 Bu t )(SiMe 3 )} 2 (μ-I)] 2 ( 9 ) and homoleptic [Ln{N(SiMe 2 Bu t )(SiMe 3 )} 3 ] (Ln = La 10, Ce 11 ) and [La{N(SiMe 2 Bu t ) 2 } 3 ] ( 12 ). The very bulky silylamide ligands described herein can impart unusual geometries to their lanthanide complexes. Complexes 10 – 12 remarkably exhibit approximate planarity in the solid state rather than the more common trigonal pyramidal shapes observed in previously reported neutral homoleptic lanthanide silylamide complexes. Complexes 1 – 12 have been variously characterized by X-ray crystallography, NMR spectroscopy, FTIR spectroscopy, and CHN microanalysis.