New pyridyl-containing amidine and specific features of its coordination to K+ and La3+ ions

Abstract

A new tridentate amidine 2-(NC₅H₄)NHC(Bu^t)=N-2,6-Me₂C₆H₃ (1) was synthesized by the reaction of 2-aminopyridine with imidoyl chloride 2,6-Me₂C₆H₃[N=C(Cl)Bu^t] in the presence of triethylamine in toluene. The deprotonation of 1 with KH in THF affords potassium amidinate {[2-(NC₅H₄)NC(Bu^t)N-2,6-Me₂C₆H₃]K}_n (2), which, according to the X-ray diffraction data, is a coordination polymer. The exchange reaction of compound 2 with anhydrous LaCl₃ gives a new homoleptic lanthanum tris(amidinate) complex La[2-(NC₅H₄)NC(Bu^t)=N-2,6-Me₂C₆H₃]₃ (3) despite the molar ratio (1 : 1). The X-ray diffraction study demonstrated that each amidinate ligand in complex 3 is coordinated to the lanthanum ion in an unusual κ²-N_Py, N mode through the nitrogen atom of the pyridine ring and one nitrogen atom of the amidinate moiety.