Synthesis and Single-Crystal X-ray Diffraction Studies on New Methylindium(III) Alkoxides

Abstract

New heteroleptic indium compounds have been synthesized starting from indium(III) halides and hexamethyldisilazyllithium to form MeXInN(SiMe3)2 [X = Cl (1), Br (2)], and then subsequent alcoholysis to afford the molecules [ClMeIn(OtBu)]2 (3), [BrMeIn(OtBu)]2 (4), {ClMeIn[O(C6H4)OMe]}2 (5), {[(SiMe3)2N]MeIn(OtBu)}2 (6) and [MeIn(OtBu)2]2 (7). The molecular structures of molecules 3–7 have been obtained by single crystal X-ray diffraction studies. The structures of the compounds 3–7 are almost identical: 3–5 crystallize in the monoclinic crystal system with two dimeric molecules per unit cell in the space group P21/c, 6 crystallizes in the monoclinic space group C2/c with four molecules per unit cell, and compound 7 crystallizes in the triclinic crystal system with one dimeric molecule per unit cell in the space group P–1. The central centrosymmetric In2O2 ring, common to all the compounds, is achieved by two bridging oxygen atoms. Due to the additional coordination by an oxygen atom of the methoxy group, the coordination number of the metal center rises from 4 to “4+1” if the OtBu ligand (compounds 3, 4, 6, and 7) is exchanged for a methoxyphenol ligand (compound 5). In addition to the In2O2 ring the compound 5 possesses two annealed five-membered InO2C2 rings. The common indium methyl group of all compounds, which is transfered by an original route from the silicon to the indium atom, is used to compare structural and spectroscopic properties of the molecules, as there is a correlation between the In–C bond length and the chemical shift of the methyl group which depends on the ligand system used.