Copper(II) complexes based on a new chelating 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine ligand: Synthesis and crystal structures. Lone pair–π, C–H···π, π–π and C–H···A (A = N, Cl) non-covalent interactions

A new bidentate chelating pyrazolylpyrimidine ligand bearing a strong electron-donating substituent, i.e. 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) ( Scheme 1), has been synthesized and used to obtain the copper(II) complexes by reaction with CuCl2. The molar ratio Cu:L = 1:2 leads to isolation of a complex having CuL2Cl2 empirical formula, while the molar ratio Cu:L = 1:1 gives a complex with CuLCl2 empirical formula. The crystal structure of L as well as the structures of both complexes were studied by single crystal X-ray diffraction. The crystal structure of CuL2Cl2 compound is formed by trans-[CuL2Cl2] mononuclear molecules. Surprisingly, in contrast to the previous compound having molecular structure, the crystal structure of CuLCl2 consists of mononuclear [CuL2Cl]+ complex cations and dinuclear [Cu2Cl6]2− anions. Thus, formula of CuLCl2 complex can be represented as [CuL2Cl]2[Cu2Cl6]. In both complexes molecules of L adopt bidentate chelating coordination mode through N2 atom of pyrazole and N3 atom of pyrimidine rings forming five-membered CuN3C metallocycles. Owing to C–H···N interactions and π–π-stacking L molecules form 2D network. In the structure of trans-[CuL2Cl2] there exist double lone pair(N(piperidine))–π(pyrimidine) interactions and C–H···Cl contacts resulting in the formation of 1D chains. Layered 2D structure of [CuL2Cl]2[Cu2Cl6] results from C–H···Cl, C–H···π and double lone pair(Cl([CuL2Cl]+ complex cation)–π(pyrimidine) interactions.

A novel chelating pyrazolylpyrimidine ligand L has been synthesized and used to obtain trans-[CuL2Cl2] and [CuL2Cl]2[Cu2Cl6] complexes. In both complexes molecules of L adopt chelating coordination mode. Owing to lone pair–π, C–H···π, π–π and C–H···A non-covalent interactions the compounds form 1D (trans-[CuL2Cl2]) or 2D (L, [CuL2Cl]2[Cu2Cl6]) network.Figure optionsDownload as PowerPoint slide