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([double bond, length as m-dash]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(-C[triple bond, length as m-dash]CPh)] 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.