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A Tripodal Trisilanol Ligand and Its Complexation Behavior towards CuI, CuII, and ZnII



A three-step synthetic route for a new tripodal branched trisilanol ligand PhSi(OSiPh2OH)3 (LH3) was developed. X-ray diffraction analysis revealed that the trisilanol crystallizes as a dimer with a cyclic hydrogen-bonding network. The reaction of LH3 with three equivalents of CunMesn (Mes = mesityl) led to a hexanuclear compound [L2Cu6] (1), which was characterized by single-crystal X-ray diffraction analysis as well as by solution NMR spectroscopy. The crystal structure of 1 revealed that the compound features a hexagonal planar CuI6 ring, which is the first of its kind in an oxygen environment. Deprotonation of the ligand with n-butyllithium and subsequent reaction with CuBr2 resulted in the dinuclear CuII complex [L′2Cu2][Li(THF2)]2 (2, THF = tetrahydrofuran), which contains a new siloxide ligand formed from L3– by the elimination of a SiOPh2 unit, as evidenced by X-ray diffraction analysis. To check if the “Ph2SiO” elimination is a general behavior of this trisilanol, the reaction with ZnBr2 was investigated under analogous conditions. However, this led to the isolation of [L2Zn2][Li(OEt)]2 (3) without any rearrangement of the siloxide ligand.