A simple approach to coordination compounds of the pentacyanocyclopentadienide anion

Deprotonation of Et(3)NH]C(5)(CN)(5)] with metal bases provides a very simple approach to coordination compounds containing the pentacyanocyclopentadienide anion C(5)(CN)(5)](-) (1). The three-dimensional polymer Na(thf)(1.5)(1)](∞) and the molecular dimer {(tmeda)(2)Na(1)}(2)] are obtained by reaction of this precursor with NaH in the presence of thf or tmeda (Me(2)NCH(2)CH(2)NMe(2)). Their single-crystal X-ray structures both reveal σ-bonded C≡N-Na arrangements and π stacking between C(5)(CN)(5)](-) ions. DFT calculations on the C(5)(CN)(5)](-) ion have been used to investigate the structures and bonding in Na(thf)(1.5)(1)](∞) and {(tmeda)(2)Na(1)}(2)]. The absence of π bonding of the metal ions in both complexes is due to dispersion of the negative charge from the C(5) ring unit to the Ctriple chemical bond]N groups in the C(5)(CN)(5)](-) ion, making the coordination chemistry of this anion distinctly different from that of cyclopentadienide C(5)H(5)(-).