TY - JOUR

T1 - A novel family of homoleptic copper(i) complexes featuring disubstituted cyanamides

T2 - A combined synthetic, structural, and theoretical study

AU - Melekhova, Anna A.

AU - Novikov, Alexander S.

AU - Panikorovskii, Taras L.

AU - Bokach, Nadezhda A.

AU - Kukushkin, Vadim Yu

N1 - Funding Information: The work was supported by the Russian Foundation for Basic Research (grant 17-03-00110). The authors thank the Center for X-ray Diffraction Studies, Center for Magnetic Resonance, Center for Chemical Analysis and Materials Research, the Center for Thermogravimetric and Calorimetric Research and Chemistry Educational Centre (all belong to Saint Petersburg State University) for the physicochemical measurements. Publisher Copyright: © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2017

Y1 - 2017

N2 - The homoleptic copper(i) complexes [Cu(NCNRR′)4](BF4) (R/R′ = Me/Me 1, Et/Et 2, C5H103, C4H8O 4, C4H85, C3H6C6H46, CH2Ph/CH2Ph 7, Me/Ph 8) featuring disubstituted cyanamides were obtained in excellent (92-97%) yields by the reaction of [Cu(NCMe)4](BF4) and 4 equivalents of NCNRR′. Complexes 1-8 were characterized by atomic absorption spectrometry (Cu%), high resolution ESI+-MS, molar conductivities, TG/DTA, and 1H, 13C{1H} NMR, FTIR spectroscopic techniques, and also by single-crystal X-ray diffraction (1, 3, and 4). Results of DFT calculations and X-ray structure determinations reveal that equilibrium geometries of [Cu(NCMe)4]+ and [Cu(NCNMe2)4]+ in the gas phase are normal tetrahedral (Td) and significantly distorted, respectively. Effects of crystal packing influence the values of the Cu-N-C angles in [Cu(NCNRR′)4]+, which points out to the noticeable contribution of the heterocumulene mesomeric form for the dialkylcyanamide copper(i) complexes. The QTAIM and NBO analyses indicate that relatively weak Cu-N contacts (15-31 kcal mol-1) in both cases exhibit single bond character and clearly polarized toward the N atom (by 91-95%). The CDA shows that the {M} ← L σ-donation substantially prevails over the {M} → L π-back-donation in both [Cu(NCMe)4]+ and [Cu(NCNMe2)4]+. The orbital, charge, and vibrational frequency arguments as well as inspection of the FTIR data suggest that the electrophilic activation of the NC group in homoleptic nitrile and dialkylcyanamide copper(i) complexes is similar, and the different behavior of nitriles and cyanamides in the 1,3-dipolar cycloaddition of ketonitrones is mainly due to the difference in the atomic charges.

AB - The homoleptic copper(i) complexes [Cu(NCNRR′)4](BF4) (R/R′ = Me/Me 1, Et/Et 2, C5H103, C4H8O 4, C4H85, C3H6C6H46, CH2Ph/CH2Ph 7, Me/Ph 8) featuring disubstituted cyanamides were obtained in excellent (92-97%) yields by the reaction of [Cu(NCMe)4](BF4) and 4 equivalents of NCNRR′. Complexes 1-8 were characterized by atomic absorption spectrometry (Cu%), high resolution ESI+-MS, molar conductivities, TG/DTA, and 1H, 13C{1H} NMR, FTIR spectroscopic techniques, and also by single-crystal X-ray diffraction (1, 3, and 4). Results of DFT calculations and X-ray structure determinations reveal that equilibrium geometries of [Cu(NCMe)4]+ and [Cu(NCNMe2)4]+ in the gas phase are normal tetrahedral (Td) and significantly distorted, respectively. Effects of crystal packing influence the values of the Cu-N-C angles in [Cu(NCNRR′)4]+, which points out to the noticeable contribution of the heterocumulene mesomeric form for the dialkylcyanamide copper(i) complexes. The QTAIM and NBO analyses indicate that relatively weak Cu-N contacts (15-31 kcal mol-1) in both cases exhibit single bond character and clearly polarized toward the N atom (by 91-95%). The CDA shows that the {M} ← L σ-donation substantially prevails over the {M} → L π-back-donation in both [Cu(NCMe)4]+ and [Cu(NCNMe2)4]+. The orbital, charge, and vibrational frequency arguments as well as inspection of the FTIR data suggest that the electrophilic activation of the NC group in homoleptic nitrile and dialkylcyanamide copper(i) complexes is similar, and the different behavior of nitriles and cyanamides in the 1,3-dipolar cycloaddition of ketonitrones is mainly due to the difference in the atomic charges.

UR - http://www.scopus.com/inward/record.url?scp=85034824413&partnerID=8YFLogxK

U2 - 10.1039/C7NJ02798B

DO - 10.1039/C7NJ02798B

M3 - Article

VL - 41

SP - 14557

EP - 14566

JO - New Journal of Chemistry

JF - New Journal of Chemistry

SN - 1144-0546

IS - 23

ER -