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Magnesium Cyanide or Isocyanide?

Gerd Ballmann, Holger Elsen, Sjoerd Harder

Angew Chem Int Ed Engl. 2019 Oct 28;58(44):15736-15741.

PMID: 31461208

Abstract:

Preference for the binding mode of the CN- ligand to Mg (Mg-CN vs. Mg-NC) is investigated. A monomeric Mg complex with a terminal CN ligand was prepared using the dipyrromethene ligand Mes DPM which successfully blocks dimerization. While reaction of (Mes DPM)MgN(SiMe3 )2 with Me3 SiCN gave the coordination complex (Mes DPM)MgN(SiMe3 )2 ⋅NCSiMe3 , reaction with (Mes DPM)Mg(nBu) led to (Mes DPM)MgNC⋅(THF)2 . A Mg-NC/Mg-CN ratio of ≈95:5 was established by crystal-structure determination and DFT calculations. IR studies show absorbances for CN stretching at 2085 cm-1 (Mg-NC) and 2162 cm-1 (Mg-CN) as confirmed by 13 C labeling. In solution and in the solid state, the CN ligand rotates within the pocket. The calculated isomerization barrier is only 12.0 kcal mol-1 and the 13 C NMR signal for CN decoalesces at -85 °C (Mg-NC: 175.9 ppm, Mg-CN: 144.3 ppm). Experiment and theory both indicate that Mg complexes with the CN- ligand should not be named cyanides but are more properly defined as isocyanides.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP4432319 MES solution MES solution 4432-31-9 Price
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