Lanthanide iodides as promoters of acetonitrile amination.: Molecular structure of MeC(=NH)NHPri, MeC(=NH)NHBut and {Dy[MeC=NH)NEt2]6}I3

Amination of acetonitrile by the amines MeNH2, (PrNH2)-N-n, (PrNH2)-N-i, (BuNH2)-N-t, and Et2NH is efficiently promoted by the lanthanide iodides LnI(2) (Ln = Nd, Dy, Tm), LnI(3) (Ln = Pr, Nd, Dy) and LnI(3)(THF)(3) (Ln = Pr, Nd, Dy). The formed mono- and NN-disubstituted amidines MeC(=NH)NHR (R = Pr-i, Bu-t), MeC(=NH)NEt2, MeC(=NR)NHR (R = Me, Pr-n) were isolated mainly as the complexes with starting iodide of general composition LnI(2)(amidine), (1) or LnI(3)(amidine)(x) (2) (x = 3-8). In the products 1, which evidently are the mixtures of LnI(2+), LnI(2)(+) and LnI(3) derivatives, the metal exists in trivalent state but one of the ligands actually is amidinate anion. A part of the generated amidines remains in the reaction solutions in free form. Heating of the 1 and 2 in vacuum at 150-200 degrees C affords corresponding amidine and the complexes with reduced amount of the amidine ligands LnI(2)(amidine)(y) (3) or LnI(3)(amidine)y (4) (y = 2-3). The products 3 and 4 displayed the same catalytic activity in the acetonitrile-amine cross-coupling as the initial iodides. SmI2 and especially YbI2 revealed lower activity. The structure of isopropylacetamidine (5), tert-butylacetamidine (6) and {Dy[MeC(=NH)NEt2](6))I-3(McCN) (7) were determined by X-ray diffraction analysis. (C) 2006 Elsevier B.V. All rights reserved.