Simple entry into N-tert-butyl-iminophosphonamide rare-earth metal alkyl and chlorido complexes

Abstract

In situ protolysis reaction of a highly basic and sterically hindered N,N′-di-tert-butyl-iminophosphonamide ligand Ph₂P(N-tBu)(NH-tBu) = (NPN^tBu)H (1) with equimolar or hemimolar amounts of rare-earth metal tris-alkyls leads to dialkyl [(NPN^tBu)Ln(CH₂SiMe₃)₂(THF)_n] (Ln = Sc, n = 0 (2), Ln = Y, n = 1 (3)) and monoalkyl species [(NPN^tBu)₂Ln(CH₂SiMe₃)] (Ln = Y (4), Nd (6), Sm (7)). One-pot reaction of [ScCl₃(THF)₃]/1/MeLi in 1/2/3 eq. ratio gives [(NPN^tBu)₂Sc(THF)CH₃] 5. Further reaction of 4 with phenylacetylene resulted in the formation of the Y-alkynyl complex [(NPN^tBu)₂Y(–CCPh)] 8. Alkyl abstraction in 2, 3 and 4 by reaction with [PhNMe₂H]⁺[B(C₆F₅)₄]⁻ resulted in the formation of cationic alkyl complex ion-pairs [(NPN^tBu)Ln(CH₂SiMe₃)(THF)_n]⁺[B(C₆F₅)₄]⁻ (Ln = Sc (9), Y (10)) and [(NPN^tBu)₂Y(THF)_n]⁺[B(C₆F₅)₄]⁻11, as confirmed by NMR data. The reaction of bis-NPN alkyl complexes with CHCl₃ is the simplest and most reliable protocol to synthesize bis-NPN-chlorido complexes [(NPN^tBu)₂Ln–Cl] (Ln = Sc (12), Y (13), Nd (14), Sm (15), Gd (16), Tb (17), Yb (18) and Lu (19)), which can become new post-metallocene alternatives to the prominent organolanthanide building blocks [Cp*₂LnX]. Partial hydrolysis of 12 leads to the formation of the oxido/chlorido-capped trinuclear complex [{(NPN^tBu)Sc(μ₂-Cl)}₃(μ₃-O)(μ₃-Cl)] 20. Molecular structures of 4, 6, 7, 13, 19 and 20 were confirmed by X-ray structure analyses.