Accessing Sodium Ferrate complexes containing neutral and anionic N-heterocyclic carbene ligands: structural, synthetic, and magnetic insights

This study reports the synthesis and single-crystal X-ray crystallographic, NMR spectroscopic, and magnetic characterization of a series of sodium ferrates using bis(amide) Fe(HMDS)2 as a precursor (HMDS = 1,1,1,3,3,3-hexamethyldisilazide). Reaction with sodium reagents NaHMDS and NaCH2SiMe3 in hexane afforded donor-solvent-free sodium ferrates [{NaFe(HMDS)3}∞] (1) and [{NaFe(HMDS)2(CH2SiMe3)}∞] (2), respectively, which exhibit contacted ion pair structures, giving rise to new polymeric chain arrangements made up of a combination of inter- and intramolecular Na···Me(HMDS) electrostatic interactions. Addition of the unsaturated NHC IPr (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) to 1 and 2 caused deaggregation of their polymeric structures to form discrete NHC-stabilized solvent-separated ion pairs [Na(IPr)2]+[Fe(HMDS)3]− (3) and [(THF)3·NaIPr]+[Fe(HMDS)2CH2SiMe3]− (4), where in both cases, the NHC ligand coordinates preferentially to Na. In contrast, when IPr is sequentially reacted with the ...