Coordination Networks Based on Tetrahedral Silane Building Blocks:  Influence of the Anion on Structures Adopted by Ag⁺−Si(<i>p</i>-C₆H₄CN)₄ Arrays

The silane tetrakis(4-cyanophenyl)silane (1) was prepared by the reaction of 4-lithiobenzonitrile with silicon tetrachloride at −100 °C. This tetrahedral molecular building block crystallizes with AgOTf (OTf = O3SCF3) from benzene and dichloromethane to give [Ag2Si(p-C6H4CN)4][OTf]2·2C6H6 (2). The extended solid structure of 2 is composed of interpenetrating "double layers" which are 3-connected via trigonal planar Ag and tetrahedral Si centers. The individual nets contain six-membered rings which are folded in one corner along a Si···Si vector to give an envelope conformation. Overall, the structure is heavily cross-linked via −CN−Ag(1)−NC−, −Ag(1)−Ag(2)−NC−, and −CN−Ag(2)(μ-O3SCF3)2Ag(2)−NC− linkages. Compound 1 also crystallizes with AgPF6, to give {Ag3[Si(p-C6H4CN)4]2}[PF6]3·1.6THF·0.5C6H6·CH2Cl2 (3). This coordination network also contains 3-connected nets, with six-membered rings in the chair conformation. These nets are interwoven to form the 3-dimensional structure. Compounds 2 and 3 are air-sensitive, and their structures are readily broken up by dissolution in acetone. The network of 2 appears to lose crystallinity when exposed to heat and vacuum (by PXRD) but nonetheless retains some properties as a molecular sieve.