Synthesis and characterization of crystalline structures based on phenylboronate ligands bound to alkaline earth cations.

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)3– coordinated to metal cations: [Ca(PhB(OH)3)2], [Sr(PhB(OH)3)2]·H2O, and [Ba(PhB(OH)3)2]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution 1H, 11B, and 13C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydr...