Schwingungsspektren und normalkoordinatenanalyse von CF3,-verbindungen : XXVI. Molekülstrukturen und schwingungsspektren von α-CF3HgN3 und CF3HgNCO

The crystal structures of the isostructural compounds α-CF₃HgN₃ (I) and CF₃HgNCO (II) were determined by X-ray methods. Centrosymmetric dimers are formed with weak Hg---n′ bonds of 2.74(2) Å in I and 2.88(2) Å in II. The Hg---N distance and Hg---N---N angle are 2.02(2) Å and 127(2)° in the monomeric fragment of I, the corresponding values in II are 2.03(2) Å and 137(2)°. Raman and, in part, IR spectra of both compounds in the solid state were recorded and assigned for Cs and C_2h symmetry of the monomers and dimers, respectively. A normal coordinate analysis proved that the stretching vibrations of the (HgN)₂ four-membered ring appeared at ≈400 and ≈75 cm^-1; the force constants amounted to ≈2.0 for the short and to ≈0.25 X 10² N/m for the long HgN bonds.