Characterization of Cu-ligand bonds in tris-pyrazolylmethane isocyanide copper(I) complexes based upon combined X-ray diffraction and theoretical study

•Synthesis of a series of the copper-isocyanide complexes [Cu(tpm∗)(CNR)](BF4).•Molecular structures of [Cu(tpm∗)(CNR)](BF4) (R = 2,6-Me2C6H3, 2-Cl-6-MeC6H3).•Theoretical study of binding in copper complexes using NBO and CDA analyses.

The complexes [Cu(tpm∗)(CNR)](BF4) (tpm∗ = tris(3,5-dimethylpyrazolyl)methane; R = Xyl [1](BF4), 2-Cl-6-MeC6H3 [2](BF4), Cy [3](BF4)) were prepared by the reaction of [Cu(NCMe)4](BF4) with tpm∗ and CNR (CH2Cl2, 20–25 °C) and these species were characterized by elemental analyses, molar conductivities, high resolution ESI+-MS, IR, 1H and 13C{1H} NMR spectroscopies and also X-ray diffraction for [1](BF4) and [2](BF4). Results of the theoretical DFT (M06/6-31G(d)) study of binding in the copper complexes using NBO and CDA analyses indicate that (i) the influence of crystal packing effects on the geometrical features of [Cu(tpm∗)(CNXyl)]+ cation is insignificant, (ii) the coordination bonds Cu–C in the tris-pyrazolylmethane isocyanide complexes are relatively strong exceeding 50 kcal/mol, and (iii) the CDA data for these systems demonstrate that the {M} ← L σ-donation prevails over the {M} → L π-back-donation.

Graphical abstractThree complexes [Cu(tpm∗)(CNR)](BF4) (tpm∗ = tris(3,5-dimethylpyrazolyl)methane; R = Xyl, 2-Cl-6-MeC6H3, Cy) were prepared. Binding in the copper complexes was studied by the theoretical DFT (M06/6-31G(d)) method.Figure optionsDownload full-size imageDownload as PowerPoint slide