Cover Picture: 1,2,4‐Triazol‐5‐ylidenes versus Imidazol‐2‐ylidenes for the Stabilization of Phosphorus(I) Cations (Z. Anorg. Allg. Chem. 22/2016)

Abstract

The cover picture illustrates the relative π‐acidity of two classes of N‐heterocyclic carbenes that have been employed to stabilize the usually very reactive P+ ion. The background depicts the packing structure of the tetraphenylborate salt of a cation featuring a P+ ion that is ligated by two 1,4‐diisopropyl‐1,2,4‐triazol‐5‐ylidene (TAZ) groups (P atoms are gold, N atoms are blue, B atoms are red, C atoms are grey). Direct comparisons of the chemical and physical properties of salts of the cations featuring TAZ ligands and those of analogous PI cations stabilized by 1,3‐diisopropylimidazol‐2‐ylidene (IMID) ligands were made using X‐ray crystallography, NMR spectroscopy and computational calculations. The data reveal a larger degree of π‐bonding across the C‐P‐C fragment in the case of the TAZ‐stabilized PI cations that is attributable to the greater π‐accepting ability of the TAZ group. More details are discussed in the article by Elnajjar et al. on pp. http://onlinelibrary.wiley.com/doi/10.1002/zaac.201600270/abstract.