Ionic liquid cations as methylation agent for extremely weak chalcogenido metalate nucleophiles† †Electronic supplementary information (ESI) available: Syntheses, experimental methods, crystallographic data, Raman spectra of compounds 1a–1f and the UV-Vis spectrum of compound 2. CCDC 1902968–1902973 and 1902904–1902906. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9sc01358j

Imidazolium-based ionic liquids served to selectively methylate terminal chalcogenide ligands of chalcogenidometalate clusters [Sn 10 S 16 O 4 (SMe) 4 ] 4– , [Mn 4 Sn 4 Se 13 (SeMe) 4 ] 6– , and [Hg 6 Te 10 (TeMe) 2 ] 6– . Selective in situ methylation of terminal chalcogenide ligands of molecular chalcogenido metalate anions in ionothermal reactions with alkylimidazolium-based ionic liquids yields a series of organo-functionalized chalcogenido metalate compounds. We present the syntheses and crystal structures of (C 4 C 1 C 1 Im) 4+ x [Sn 10 S 16 O 4 (SMe) 4 ][An] x ( 1a–1f ), (dmmpH) 6 [Mn 4 Sn 4 Se 13 (SeMe) 4 ] ( 2 ), and (C n C 1 Im) 6 [Hg 6 Te 10 (TeMe) 2 ] ( 3a , 3b ). The methylation was confirmed by Raman spectroscopy, and the optical absorption properties of the methylated compounds were determined and compared to purely inorganic analogs.