Anion–Anion Interactions in the Crystal Packing of Functionalized Methanide Anions: An Experimental and Computational Study

Abstract

Examination of the crystal structures of (Me4N)(dcnm) (1), (Me4N)(dcnom) (2), and (Me4N)(nbdm) (3) [dcnm = dicyanonitrosomethanide, dcnom = dicyanonitromethanide, nbdm = nitroso-N,N-bis(dicyanomethanide)] reveals the anions pack in an unusual columnar array, with distances between the planar species suggestive of π–π stacking. This columar packing motif is not observed in the crystal structures of (Me4N)(ccnm) (4) and (Me4N)(ccnom) (6) (ccnm = carbamoylcyanonitrosomethanide, ccnom = carbamoylcyanonitromethanide), in which hydrogen bonding between anions is the dominant supramolecular interaction. Ab initio calculations performed at the HF and MP2 levels of theory on ionic clusters of varying size further explored the nature and strength of anionic interactions observed in crystal structures. The first syntheses of the nbdm and ccnom anions are also reported.

An ab initio Study of the Structure and Energetics of Hydrogen Bonding in Ionic Liquids

“…It is well-known that the gas phase destabilizes electrostatic interactions and therefore seeks to reduce them, usually by favoring the back proton transfer from the cation to the anion in protic ionic liquids, thus forming neutral species. The use of implicit solvent has been demonstrated to lead to more energetically stable complexes of predominantly ionic nature (Mackerell et al, 2004; Chesman et al, 2014). A well-known example is the preference of amino acids to adopt the zwitterionic form in aqueous media, whereas in the gas phase they are optimized to be neutral (Stover et al, 2012).…”

Interaction between Trinuclear Regium Complexes of Pyrazolate and Anions, a Computational Study

“…We will investigate the interaction of (Pz-M) 3 , M = Cu, Ag and Au, with three anions (F − , Cl − and Br − ) limiting to the lowest oxidation states (I) of the three coinage metals ( Figure 2). On a different topic, interaction between charged systems, i.e., anion-anion and cation-cation are very interesting, and were found both within the gas phase [69][70][71][72][73][74][75][76][77][78][79] and crystal structures [80,81]. This rare type of interaction, which, in principle should be repulsive, should lead to unstable complexes, i.e., they will revert into the separated ions.…”

Synergistic and Antagonistic Ligand Effects in the Transformation of Silver Compounds of Keto‐ and Cyano‐Functionalised Oximates and Nitronates: A Systematic Study Using Thermal Analysis

“…The silver compounds of 1, [10] 2, [11] 3, [12] 4 [13] and 6 [14] were prepared according to published procedures. Detailed information concerning elemental analysis and NMR spectroscopic data is given in the Supporting Information.…”

“…Structure determinations from X-ray investigations of single crystals are available for a number of these compounds (complexes of 1, [10] 2, [11] 3, [12] 4 [13] and 6). [14] In the solid state, coordination polymers are present, in which the silver atoms are bonded to the functional groups of different ligands.…”