Lanthanide(iii) and group 13 metal ion complexes of tripodal amino phosphinate ligands

Abstract

The tripodal amino-phosphinate ligands, tris(4-(phenylphosphinato)-3-benzyl-3-azabutyl)amine (H₃ppba·2HCl·H₂O) and tris(4-(phenylphosphinato)-3-azabutyl)amine (H₃ppa·HCl·H₂O) were synthesized and reacted with Al³⁺, Ga³⁺, In³⁺ and the lanthanides (Ln³⁺). At 2 : 1 H₃ppba to metal ratios, complexes of the type [M(H₃ppba)₂]³⁺ (M = Al³⁺, Ga³⁺, In³⁺, Ho³⁺–Lu³⁺) were isolated. The bicapped [Ga(H₃ppba)₂](NO₃)₂Cl·3CH₃OH was structurally characterized and was shown indirectly by various techniques to be isostructural with the other [M(H₃ppba)₂]³⁺ complexes. Also, at 2 : 1 H₃ppba to metal ratios, complexes of the type [M(H₄ppba)₂]⁵⁺ (M = La³⁺–Tb³⁺) were characterized, and the X-ray structure of [Gd(H₄ppba)₂](NO₃)₄Cl·3CH₃OH was determined. At 1 : 1 H₃ppba to metal ratios, complexes of the type [M(H₄ppba)]⁴⁺ (M = La³⁺–Er³⁺) were isolated and characterized. Elemental analysis and spectroscopic evidence supported the formation of a 1 : 1 monocapped complex. Reaction of 1 : 1 ratios of H₃ppa with Ln³⁺ and In³⁺ yielded complexes of the type [M(H₃ppa)]³⁺ (M = La³⁺–Yb³⁺) but with Ga³⁺, complex of the type [Ga(ppa)]·3H₂O was obtained. Reaction of 1 : 1 ratios of H₃ppa with Ln³⁺ and In³⁺ yielded complexes of the type [M(H₃ppa)]³⁺ (M = La³⁺–Yb³⁺) but with Ga³⁺ a neutral complex [Ga(ppa)]·3H₂O was obtained. The formation of an encapsulated 1 : 1 complex is supported by elemental analysis and spectroscopic evidence.