Sawhorse connections in a Ag(I)-nitrite coordination network: {[Ag(pyrazine)] NO₂}(∞)

The Ag(I) coordination networks, {[Ag(pyrazine)]NO2}∞ and {[Ag(4,4′-bipy)]NO2}∞ have been constructed in order to investigate the effect of anion upon network topology; an unusual sawhorse connection is observed in the structure of {[Ag(pyrazine)]NO2}∞ with the nitrite anion acting to ‘block’ cis coordination sites. The preparation of extended networks using inorganic coordination polymers has become an area of increasing study in recent years One of the reasons that this interest has arisen is because the synthetic procedure used to construct these materials allows a high degree of design. Ultimately this may lead to the development of materials with tuneable properties including structures with host–guest properties similar to those observed with zeolites and compounds with interesting electronic or magnetic properties. The high degree of design arises from the coupling of the well understood coordination properties of individual metal ions and highly-developed ligand syntheses with the newer areas of supramolecular chemistry and crystal engineering We have been studying the effect of individual building-blocks upon network structure. This has included the control of network topology and interpenetration in adamantoid networks via ligand desig and studies on the effect of variation of solvent of crystallisation upon network structure The nature of the counter-anion has also been shown to have a dramatic effect upon network topology and this is particularly noticeable in Ag(I) chemistry Recently we have demonstrated that replacement of AgBF4 or AgPF6 with AgNO3 results in a fundamental change of the extended structure of a coordination polymer with the ligand 3,6-di-4-pyridyl-1,2,4,5-tetrazine due to interactions between the Ag(I) centre and the NO3- anion to give a ‘helical staircase’ structure We now report the extension of these investigations to the use of AgNO2, and report an unusual example of a sawhorse connection within an extended network.