Organometallic crystal engineering with multidentate building blocks and template guest size effect.: Supra-anionic organic frameworks obtained from cyclobutane-1,2,3,4-tetracarboxylic and trans-acotinic acids

The organic acids cyclobutane-1,2,3,4-tetracarboxylic C4H4(CO2H)(4), and trans-acotinic acid C3H3(CO2H)(3), have been treated in thf with the organometallic hydroxides [Co(eta(5)-C5H5)(2)](+)[OH](-), [Co(eta(5)-C5Me5)(2)](+)[OH](-), and [Cr(eta(6)-C6H6)(2)](+)[OH](-) prepared in situ from the oxidation of the corresponding neutral complexes, to yield the novel organic-organometallic crystalline materials [Co(eta(5)-C5H5)(2)](+)[C4H4(CO2H)(3)COO](-) 1, [Cr(eta(6)-C6H6)(2)](+)[C4H4(CO2H)(3)CO2](-). H2O 2, and [Co(eta(5)-C5Me5)(2)](+)[C3H3(CO2H)(2)CO2(H). C3H3(CO2H)(2)CO2](-). H2O 3. Self-assembly of the monodeprotonated organic acid C4H4(CO2H)(4) generates supra-anionic framework structures held together by O-H ... O and O-H ... O- hydrogen bonds which accommodate the diamagnetic [Co(eta(5)-C5H5)(2)](+) and paramagnetic [Cr(eta(6)-C6H6)(2)](+) cations, respectively. Crystalline 1 does not form single crystals with defined shapes but rather an "enamel" like material which grows parallel to the crystallographic bc plane. The same reaction between trans-acotinic acid and [Co(eta(5)-C5Me5)(2)](+)[OH](-)generates a large honeycomb-type structure in [Co(eta(5)-C5Me5)(2)](+)[C3H3(CO2H)(2)CO2(H). C3H3(CO2H)(2)CO2](-). H2O 3. The effect of the size of the templating units [Co(eta(5)-C5H5)(2)](+) and [Co(eta(5)-C5Me5)(2)](+) is discussed. The previously unknown structure of the starting material [Co(eta(5)-C5Me5)(2)](+)[PF6](-) 4, used for the preparation of [Co(eta(5)-C5Me5)(2)](+)[OH](-), has also been determined.