Synthesis, vibrational spectra and single-crystal structure determination of lithium tricyanomethanide Li[C(CN)3]

Abstract The long-elusive structure of lithium tricyanomethanide Li[C(CN) 3 ] has been determined on the basis of material synthesized via a metathesis reaction of Ag[C(CN) 3 ] with LiCl in water driven by AgCl precipitation and subsequently recrystallization from methanol. Li[C(CN) 3 ] crystallizes in the non-centrosymmetric orthorhombic space group Ima 2 with the unit-cell parameters a =751.06(4), b =1059.75(6) and c =563.27(3) pm adopting a unique structure with planar [C(CN) 3 ] − anions exhibiting nearly ideal trigonal planar D 3 h symmetry. The Li + cations are coordinated by five independent tricyanomethanide anions forming a distorted square pyramid with Li–N distances between 202 and 249 pm. The vibrational frequencies were also determined and along with other properties of Li[C(CN) 3 ] compared with those of related compounds.