Syntheses, Crystal Structures and Adsorption Properties of Ultramicroporous Coordination Polymers Constructed from Hexafluorosilicate Ions and Pyrazine

Three novel coordination polymers based on M 2+ (M = Cu, Zn), pyrazine (pyz) and the SiF 6 2– ion, [Cu(SiF 6 )(pyz)(H 2 O) 2 ] n ( 1a ), {[Cu(SiF 6 )(pyz) 3 ] · 2H 2 O} n ( 1b blabla 2H 2 O) and {[Zn(SiF 6 )(pyz) 2 ] · 2MeOH} n ( 2 blabla 2MeOH), have been synthesized and characterized by single‐crystal X‐ray diffraction analyses. Compound 1a forms straight one‐dimensional chains of–Cu(OH 2 ) 2 –pyz–, which are bridged by SiF 6 2– ions to produce two‐dimensional sheets. Compound 1b blabla 2H 2 O forms straight two‐dimensional sheets of –Cu(pyz) 2 –pyz– chains bridged by SiF 6 2– ions, where perpendicularly protruding pyz planes are stacked to produce a three‐dimensional framework with 2.5 × 2.2 Å 2 pores. In compound 2 blabla 2MeOH, grids of [Zn(pyz) 2 ] n are bridged by SiF 6 2– ions axially coordinating to Zn 2+ ions to produce an open three‐dimensional framework. The 4.5 × 4.5 Å 2 pores in 2 blabla 2MeOH are surrounded by pyz panels, and they remain intact after removal of solvents to give [Zn(SiF 6 )(pyz) 2 ] n ( 2 ). The permanent porosity of 2 was characterized by adsorption studies with solvent vapours such as MeOH (kinetic diameter 3.8 Å), EtOH (4.3 Å), i PrOH (4.7 Å) and Me 2 CO (4.7 Å), showing a size‐exclusive effect at around 4.7 Å. Furthermore, the H 2 adsorption/desorption isotherm of 2 at 77 K shows a sharp uptake with a slight hysteresis loop, which is attributed to both the small size of the pore and the interaction between H 2 molecules and fluorine (SiF 6 2– ) atoms that are exposed on the pore surfaces. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)