Open-chain hemiketal is stabilized by coordination to a copper (II)

Abstract The hemiketal complex [Cu{NH2C(Me)2C(Ph)(OMe)O}2] (1) was generated by the reaction of [Cu(NCMe)4](BF4) and 4 equivs of 2,2-dimethyl-3-phenyl-2H-azirine in the presence of NCNMe2 in wet MeOH and isolated in 92% yield. In 1, the in situ formed hemiketal NH2C(Me)2C(Ph)(OMe)OH in its deprotonated form is stabilized due to chelation to copper(II). In the X-ray structure of 1 4MeOH, the intermolecular hydrogen bonding was detected between O and N atoms of the organic ligand and the H O group of solvated MeOH as well as between two molecules of the solvated MeOH. Three types of hydrogen bonds in the obtained structure were studied by the DFT calculations (M06/6-31 ++G** level of theory, MDF10 pseudopotentials on the Cu atoms) and topological analysis of the electron density distribution within the formalism of Bader's theory (QTAIM method). Estimated strength of these non-covalent interactions is 3–9 kcal/mol.