A Thorough Characterization of the Tellurocyanate Anion

Abstract Tellurocyanate, [TeCN] − , is the heaviest group 16 congener of the cyanate anion, [OCN] − . Due to the relative instability of the C─Te bond, tellurocyanate chemistry has seen only scarce attention. Here, we present the facile synthesis and thorough characterization of [K@crypt‐222][TeCN]. The anion is essentially linear with interatomic distances C─N = 1.150(6)Å and C─Te = 2.051(4)Å, thus approximating a C≡N triple bond and for C─Te a bond order between 1 and 2. Fully 13 C and 15 N labeled [Te 13 C 15 N] − allowed for the extraction of chemical shifts and all possible coupling constants ( 13 C = 77.8 ppm, 15 N = 285.7 ppm, 125 Te = −566 ppm, 1 J 13C‐15N = 8 Hz, 1 J 13C‐125Te = 748 Hz, 2 J 15N‐125Te = 55 Hz), which were also determined independently by quantum chemical calculations. In the series [ Ch CN] − ( Ch = O─Te), [TeCN] − shows the strongest spin‐orbit coupling (SOC) induced heavy‐atom effect on the light‐atom shielding (SO‐HALA‐effect). In contrast, 15 N shifts are also well described without considering relativistic effects and/or SOC. Negative‐ion photoelectron spectroscopy was used to extract the electron affinity (EA = 3.034 eV) and spin‐orbit splitting (3807 cm −1 ) of [TeCN] • . These values continue the trends of falling EA and rising SOC in the series [ Ch CN] • .