New polyhedral zinc siloxanes:: Synthesis and x-ray crystal structures of Zn8Me7(dioxane)2(O3SiR)3 and [Zn7Me2(THF)5(O3SiR)4] [R = (2,6-i-Pr2C6H3)N(SiMe3)]

In continuation of our previous work on the synthesis of zinc siloxanes to understand the influence of stoichiometry in the assembly of polyhedral zinc siloxanes, we have carried out two different reactions between RSi(OH)(3) [R = (2,6-i-Pr2C6H3)N(SiMe3)] and ZnMe2 in molar ratios of 1:3 and 1:1.75. In these reactions, we have isolated an octanuclear ZnsMe(7)(dioxane)(2)(O3SiR)(3) (5) and a heptanuclear zinc siloxane [Zn7Me2(THF)(5)(O3SiR)(4)] (6), respectively. Compound 5 is a complex cage structure and can be understood as being a derivative of a drum-shaped species containing a Zn7Si3O9 core. In contrast, 6 consists of a Zn4Si4O12 unit with zinc and silicon atoms occupying alternate corners of the cube; three contiguous faces of this cube are capped by zinc atoms, leaving the other three faces open.