Reduction of Sterically Hindered β-Diketiminato Europium(iii) Complexes by the β-Diketiminato Anion: A Convenient Route for the Synthesis of β-Diketiminato Europium(ii) Complexes

The metathesis reaction of anhydrous EuCl(3) with sodium salt of bulky β-diketiminato NaL (L = [N(2, 4, 6- Me(3)C(6)H(2))C(Me)](2)CH(-), L(2, 4, 6-Me3); [N(2,6-(i)Pr(2)C(6)H(3))C(Me)](2)CH(-), L(2, 6-ipr2) and [(2, 6-(i)Pr(2)C(6)H(3))NC(Me)CHC(Me)N(C(6)H(5))](-), L(2, 6-ipr2)(Ph)) in THF at 60 °C afforded the corresponding Eu(II) complexes: Eu(II)(L(2, 4, 6-Me3))(2)(THF) (1), Eu(II)(L(2, 6-ipr2))(2) (2) and Eu(II)(L(2, 6-ipr2)(Ph))(2) (5) with the formations of dimers (L(2, 4, 6-Me3))(2) (3) and (L(2, 6-ipr2))(2) (4) for the former two reactions and proligand L(2, 6-ipr2)(Ph)H (6) for the latter one. Compounds 1-6 were confirmed by an X-ray crystal structure analysis. The central metal Eu(II) in 1 is coordinated by two monoanionic L(2, 4, 6-Me3) ligands and one THF molecule in a trigonal bipyramid. The Eu(II) in each of 2 and 5 is ligated by two monoanionic ligands to form a tetrahedral geometry. The BVS (Bond Valence Sum) calculation indicates the oxidation state of Eu in all the three complexes is 2+ (2.12 for 1, 1.86 for 2 and 1.99 for 5). The isolation of dimers of (L(2, 4, 6-Me3))(2) and L(2, 6-ipr2))(2) and proligand L(2, 6-ipr2)(Ph)H demonstrates that the reducing agent in the present reduction of a Eu(III) ion to a Eu(II) ion might be the (L(2, 4, 6-Me3))(-), (L(2, 6-ipr2))(-) and (L(2, 6-ipr2)(Ph))(-), respectively. The possible mechanism for the reduction pathway is presented.