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 tr ans-acotinic acid C3H3(CO2H)(3), have been treated in thf with the organome tallic 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 oxidat ion of the corresponding neutral complexes, to yield the novel organic-orga nometallic 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)-C 5Me5)(2)](+)[C3H3(CO2H)(2)CO2(H). C3H3(CO2H)(2)CO2](-). H2O 3. Self-assembl y of the monodeprotonated organic acid C4H4(CO2H)(4) generates supra-anioni c framework structures held together by O-H ... O and O-H ... O- hydrogen b onds which accommodate the diamagnetic [Co(eta(5)-C5H5)(2)](+) and paramagn etic [Cr(eta(6)-C6H6)(2)](+) cations, respectively. Crystalline 1 does not form single crystals with defined shapes but rather an "enamel" like materi al 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)CO 2(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. T he 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.