CO₂ Template Synthesis of Metal Formates with a ReO₃ Net

The serendipitous discovery of CO2 as a template in the fabrication of ferric formate (1) has led to the preparation of serial metal(III) formates [MIII(HCOO)3·3/4CO2·1/4H2O·1/4HCOOH ]∞ (M = Fe(1), Al (2), Ga (3), and In(4)). The X-ray single-crystal determinations showed that the metals have octahedral geometries and are linked by HCOO- in the anti−anti style into a 3D ReO3 net, where CO2 molecules exist in cages of mmm symmetry and are hydrogen bonded to the formic CH groups. An X-ray powder diffraction (XRD) study revealed that 2 is identical to the documented [Al(HCOO)3·xH2O]. Further synthetic experiments and 13C NMR spectroscopy eventually confirmed that 2 should be formulated as [Al(HCOO)3·3/4CO2·1/4H2O·1/4HCOOH ]∞, which for decades had been mistakenly given as [AlIII(HCOO)3·xH2O].