Lithium and lanthanum complexes with acenaphthylene dianion. Molecular structure of [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 complex

Abstract

The lithium complex with the acenaphthylene dianion [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 (1) was synthesized by the reduction of acenaphthylene with lithium in diethyl ether. According to the X-ray diffraction data, compound 1 has a reverse-sandwich structure with the bridging dianion μ2:η3[Li(η3:η3-C12H8)]2. Two lithium atoms in complex 1 are located between two coplanar acenaphthylene ligands of the μ2:η3[Li(η3:η3-C12H8)]22– dianion and are η3-coordinated with the five- and six-membered rings. The lanthanum complex with the acenaphthylene dianion [LaI2(THF)3]2(μ2-C12H8) (2) was synthesized by the reduction of acenaphthylene in THF with the lanthanum(iii) complex [LaI2(THF)3]2(μ2-C10H8) containing the naphthalene dianion. The 1H NMR spectrum of complex 2 in THF-d8 exhibits four signals of the acenaphthylene dianion, whose strong upfield shifts compared to those of free acenaphthylene indicate the dianionic character of the ligand. The highest upfield chemical shift belongs to the proton bound to the C atom on which, according to calculation, the maximum negative charge is concentrated.