Solvated copper(I) hexafluorosilicate π-complexes based on [Cu2(amtd)2]2+ (amtd = 2-allylamino-5-methyl-1,3,4-thiadiazole) dimer

• Three novel copper(I) hexafluorosilicate π-complexes with amdt ligand are prepared.
• Single crystal X-ray diffraction revealed two geometries of [Cu2(amdt)2]2+.
• Chelate-bridging role of the ligand leads to extreme stability of [Cu2(amdt)2]2+.
• Raman spectra were analyzed on the basis of quantum-chemical calculations.

[Cu2(amdt)2]SiF6·C6H6 and [Cu2(amdt)2(H2O)2]SiF6·CH3CN·2H2O (amdt = 2-allylamino-5-methyl-1,3,4-thiadiazole) were obtained by alternating-current electrochemical synthesis, starting from water–acetonitrile–benzene mixtures containing 2-allylamino-5-methyl-1,3,4-thiadiazole and CuSiF6·4H2O. The electrochemical reduction of the saturated copper hexafluorosilicate water solution beneath the neatly poured layer of acetonitrile-benzene amdt solution resulted in the formation of crystalline [Cu2(amdt)2]SiF6·C6H6. The initial stirring of the same mixture before subjecting it to the electrochemical reduction resulted in the formation of [Cu2(amdt)2(H2O)2]SiF6·CH3CN·2H2O. A sluggish hydrolysis of the acetonitrile over 2 years in a closed test tube with [Cu2(amdt)2]SiF6·C6H6 crystals in a mother liquor resulted in the formation of [Cu2L2(H2O)2]SiF6·CH3CONH2·2H2O. All the compounds were studied using X-ray single-crystal diffraction and Raman spectroscopy. The molecular structures and the Raman spectra of the compounds were discussed on the basis of computational modeling with the DFT/B3LYP/cc-pVDZ method.

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