Crystal structure, thermal analysis and spectroscopic properties of Tetrabutylammonium 3,5-bis(dicyanomethylene)-cyclopentane-1,2,4-trionate: An intriguing pseudo-oxocarbon and its zinc(II) complex

The synthesis, thermal behavior, spectroscopic properties and crystal structure of tetrabutylammonium Croconate Violet, (NBu4)2CV, are described. This compound crystallizes in the triclinic space group P1¯ with a=12.440(1), b=19.003(2), c=19.679(2) Å; α=72.809(4), β=77.037(4), γ=84.702(6)° and Z=4. Additionally, from the reaction between (NBu4)2CV and ZnCl2, the first Zn(II) complex containing the CV2− dianion, (NBu4)4[Zn(CV)3] was obtained. The complex was characterized by infrared and Raman spectroscopic techniques as well as by 1H and 13C NMR analysis. These data show that the coordination of pseudo-oxocarbon to the metal center occurs through the vicinal oxygen atoms in a chelating fashion while the nitrile groups are not involved in the formation of the complex.