Half-Sandwich Lanthanide(III) Complexes Coordinated by Two α-Iminopyridine Radical Anions

The reaction of ytterbocene (C5H4Me)2Yb(THF) with 2 equiv of N-2,6-diisopropylphenylimino-2-pyridine (Ipy) occurs with oxidative cleavage of one Yb−Cp bond and oxidation of the ytterbium(II) ion and affords the half-sandwich Yb(III) complex [Yb(C5H4Me){(2,6-i-Pr2C6H3NCH(C5H4N)•−}2], containing two Ipy radical-anions. The indenyl-containing analogue [Yb(C9H7){(2,6-i-Pr2C6H3NCH(C5H4N)•−}2] was unexpectedly obtained in the metathesis reaction of (C9H7)2Yb(μ-Cl)2Li(Et2O)2 with an equimolar amount of [Ipy•−]K+ instead of the sandwich Yb(III) complex [Yb(C9H7)2{(2,6-i-Pr2C6H3NCH(C5H4N)•−}]. The gadolinium complex [Gd(C5Me5){(2,6-i-Pr2C6H3NCH(C5H5N)•−}2] was synthesized by the metathesis reaction of (C5Me5)GdCl2(THF)3 with a 2-fold molar excess of [Ipy•−]K+ in THF. The structures of all complexes were proved by the X-ray single-crystal diffraction studies. The investigation of magnetic properties of complexes [LnCp{(2,6-i-Pr2C6H3NCH(C5H4N)•−}2] (Cp = C5H4Me, C5Me5, C9H7; Ln = Yb, Gd) in the temperature region 2−300 K revealed the presence of two types of antiferromagnetic interactions between the paramagnetic centers: between the Ln3+ ion and both radicals and between two radicals.