Synthesis and structures of lithium salts of two cluster iodoarsenate(III)s and a periodohexaantimonate(III)

Treatment of the lithium β-diketiminate Li[{N(C6H3 Pr 2 i -2,6)C(Me)}2CH] with an equivalent portion of arsenic(III) iodide unexpectedly afforded [Li(thf)4]2[As8I26] (1) in modest yield. Another new cluster anion featured in [Li(thf)4]2[Li(thf)6][As7I24]·1.5(thf) (2) was obtained in excellent yield from lithium iodide and four equivalents of AsI3 in thf. Using the same stoichiometry and solvent, but with SbI3 in place of AsI3, furnished in good yield [Li(thf)4]4[Sb6I22]·2(thf) (3). The structures of the new crystalline orange (1, 3) or orange/red (2) salts was established by single crystal X-ray diffraction. Each anion of 1–3 may be factorised into respectively [(AsI2)6(AsI)2(μ2-I)10(μ5-I)2]2− (1), [{(AsI2)(μ2-I)(μ3-I)}6As]3− (2) and [(SbI3)2(SbI2)2(SbI)2(μ2-I)6(μ3-I)4]4− (3). Each As atom in 2 and each Sb atom in 3 is the centre of a six-coordinate distorted octahedron, while the arsenic atoms in 1 have either four- or six-coordinate environments.