Homoleptic Trichloroacetonitrile Complexes

Two homoleptic cationic trichloroacetonitrile complexes [M(NCCCl3)(4)](+) [M+ = Li+ (1), Ag+ (2)] were synthesized through stabilization with the salts of the weakly coordinating anion [Al(ORF)(4)](-)(RF = -C(CF3)(3)). The successful determination of the structures of these two complexes by single-crystal X-ray diffraction (SC-XRD) showed a weak interaction between the weakly coordinating anion (WCA) and the singly charged cation. In case of the more stable lithium compounds, a characterization with vibrational spectroscopy was also possible. The SC-XRD and Raman data proved a lower coordination power of Cl3CCN compared to MeCN. Calculations at PBE0/def2-TZVPP level indicate that it should lie between MeCN and CH2Cl2 for the coordination in a model silver(I) complex [Ag(L)(2)](+) (L = MeCN, Cl3CCN, CH2Cl2). Calculation of the free Gibbs reaction energies of the formation of the bis-acetonitrile, bis-trichloroacetonitrile and the tetrakis-trichloroacetonitrile complexes, that were found in the solid state with and without dispersion correction (D3) showed a large effect of dispersion effects on the stability of the trichloroacetonitrile complexes. These results indicate that Cl3CCN can be used as weak ligand for metal cations and can be a potentially useful weakly coordinating solvent, if the relatively strong coordination power of MeCN is unwanted. An attempt to synthesize a [Au(NCCCl3)(n)](+) complex through the reaction of [NO](+)[Al(ORF)(4)](-) with elemental gold led to decomposition of the [Al(ORF)(4)](-) anion and formation of Cl3(C)CN -> Al(ORF)(3) (3).