Crystallographic Insight into the Mg²⁺ Coordination Mode and N(SO₂CF₃)₂^– Anion Conformation in Mg[N(SO₂CF₃)₂]₂ and Its Adducts

Abstract

Magnesium bis(trifluoromethylsulfonyl)amide (Mg[TFSA] 2 ) and its adducts ([Mg(L) n ][TFSA] 2 ) with common ligands (L) such as ethanol, ethyl acetate, and water, namely [Mg(C 2 H 5 OH) 4 ][TFSA] 2 , [Mg(C 2 H 5 OH) 6 ][TFSA] 2 , [Mg(C 2 H 5 OOCCH 3 ) 2 ][TFSA] 2 , [Mg(H 2 O) 2 ][TFSA] 2 , and [Mg(H 2 O) 6 ][TFSA] 2 (H 2 O) 2 , have been prepared and characterized by single‐crystal X‐ray diffraction and Raman spectroscopy. In every case, Mg 2+ is octahedrally coordinated by six O atoms of TFSA – and/or the ligand. The crystal structure of Mg[TFSA] 2 indicates the presence of disordered cis (12 %) and trans (82 %) ligand anion conformers. [Mg(C 2 H 5 OH) 4 ][TFSA] 2 appears to be a new example of a coordination compound in which the TFSA – anions adopt a trans conformation while bonded to the metal core. The crystallographic data has allowed us to propose a scheme of stepwise σ‐donor ligand coordination to the Mg 2+ core in Mg[TFSA] 2 and [Mg(L) n ][TFSA] 2 salts. This scheme is consistent with the literature data and indicates that the conformation of TFSA – anions in [Mg(L) n ][TFSA] 2 depends on the number of ligands coordinated to the Mg 2+ core, regardless of the ligand.