Deprotonation from an OH on myo-Inositol Promoted by ?2-Bridgeswith Possible Regioselectivity/Chiral Selectivity

Single-crystal structures of myo-inositol complexes with erbium ([Er2(C6H11O6)2(H2O)5Cl2]Cl2(H2O)4, denoted ErIhereafter) and strontium (Sr(C6H12O6)2(H2O)2Cl2, denoted SrIhereafter) are described. In ErI, deprotonation occurs on an OH ofmyo-inositol, although the complex is synthesized in an acidicsolution, and the pKavalues of all of the OHs inmyo-inositol arelarger than 12. The deprotonated OH is involved in a mu 2-bridge.The polarization from two Er3+ions activates the chemicallyrelatively inert OH and promotes deprotonation. In the stableconformation ofmyo-inositol, there arefive equatorial OHs andone axial OH. The deprotonation occurs on the only axial OH,suggesting that the deprotonation possesses characteristics ofregioselectivity/chiral selectivity. Two Er3+ions in the mu 2-bridge arestabilized byfive-membered rings formed by chelating Er3+with an O-C-C-O moiety. As revealed by the X-ray crystallographystudy, the absolute values of the O-C-C-O torsion angles decrease from similar to 60 to similar to 45 degrees upon chelating. Since the O-C-C-Omoiety is within a six-membered ring, the variation of the torsion angle may exert distortion of the chair conformation. Quantumchemistry calculation results indicate that an axial OHflanked by two equatorial OHs (double ax-eq motif) is favorable for theformation of a mu 2-bridge, accounting for the selectivity. The double ax-eq motif may be used in a rational design of high-performance catalysts where deprotonation with high regioselectivity/chiral selectivity is carried out

Automated summary

This study describes the single-crystal structures of complexes formed by erbium and strontium with myo-inositol. The deprotonation of one hydroxyl group in myo-inositol occurs, which is involved in the formation of a mu 2-bridge. The polarization from two Er3+ ions activates the chemically inert hydroxyl group and promotes deprotonation. The deprotonation reaction shows regioselectivity/chiral selectivity. The double ax-eq motif can be used for the rational design of high-performance catalysts with high regioselectivity/chiral selectivity.