[Sn_(17){GaCl(ddp)}4]: A High-Nuclearity Metalloid Tin Cluster Trapped by Electrophilic Gallium Ligands

摘要

The kinetically controlled disproportionation of the metasta-ble subvalent heavier Group 13 and 14 halides produces a library of species on the way to the elemental form. A rich variety of these intermediates were isolated in the form of ligand-stabilized metalloid clusters of the type [E_aR_b (a > b, R = 2,6-Mes2C6H3, N(SiMe3)2, Cp~*, etc.), including fascinating Group 13 giant clusters, such as [Al_(50)Cp~*_(12)] , [Al_(77){N-(SiMe3)2}_(20)]~(2-), and [Ga_(84){N(SiMe3)2}_(20)]~(4-). The highest nuclearity cluster of the neighboring Group 14 elements discovered to date is [Sn_(15)R6] (R = N(2,6-iPr2C6H3)(SiMe2X); X = Me, Ph). Of several synthetic strategies to form clusters of the general formula [Sn_aR_b] (R: various bulky substitu-ents), namely [Sn7R2], [Sn8R4],[Sn8R6], [Sn9R3], and [Sn_(10)R3] , the most relevant is reductive coupling of RSnCl or RSnCl3 precursors with or without additional SnCl2 using a strong reducing agent (alkali metals, NaC_(10)H8, K8C, Li[BHsBu3], etc.). However, these reactions are typically very difficult to control. The steric and the electronic nature of the ligand R plays a crucial role in the size and structural type of the formed clusters. However, the yield of these heterogeneous reductions is usually very low owing to the potentially destructive radical reactions on the strongly reductive metal surfaces.