Hexahalometallate salts of trivalent scandium, yttrium and lanthanum: cation–anion association in the solid state and in solution. (29th June 2016)

• Record Type: Journal Article
• Authors: Champion, Martin J. D.; Levason, William; Pugh, David; Reid, Gillian
• Is Part Of: New journal of chemistry. Volume 40:Number 8(2016:Aug.)
• Page Start: 7181
• Page End: 7189
• Publication Date: 2016-06-29
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c6nj01068g
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : The hydrogen bonding of hexahalometallate anions with various organic cations is explored via crystallographic and solution NMR studies. Abstract : The hexahalide salts, [N n Bu4 ]3 [LaCl6 ], [BMPYRR]3 [LaCl6 ] (BMPYRR = 1-butyl-1-methylpyrrolidinium), [EMIM]3 [MX6 ] (EMIM = 1-ethyl-3-methylimidazolium; M = La, X = Cl, Br, I; M = Sc, Y, Ce, X = Cl) and [EDMIM]3 [MX6 ] (EDMIM = 1-ethyl-2, 3-dimethylimidazolium; M = Y, X = Cl; M = La, X = Cl, I) have been prepared and X-ray crystal structures determined for several of them, with a view to probing the effect of varying the trivalent metal ion, the halide and the counter-cation on the structures adopted in the solid state. The crystal structures of the EMIM and EDMIM salts show extensive H-bonding between the halide ligands and organic cations; based upon the H-bonding distances, this appears to be strongest for the [EMIM]3 [MCl6 ] salts, becoming progressively weaker for heavier metal ion or halide. In terms of the cations, changing from EMIM to EDMIM also reduces the strength of the H-bonding. The strength of the cation–anion pairing in solution has also been probed in solution via NMR spectroscopy where possible ( 45 Sc, 89 Y and 189 La) and, for the EMIM salts, via the shift of δ (H2) relative to [EMIM]Cl at a standard concentration. The trends observed in solution mirror those determined in the solid state.