Recently it was shown that water and air stable perrhenate based ionic liquids (ILs) are promising catalysts for oxidation reactions. For a broader application and in the context of green chemistry it is important to study in addition to their technical performance also their potential impact on environment and human health. This paper presents the first account on (eco)toxicological and biodegradation data for a set of ammonium and imidazolium based ILs with perrhenate anions. Fig. 1 Illustration of the ammonium-and imidazolium perrhenates used in the study: [NBu 4 ][ReO 4 ] (1), [BnBnIm][ReO 4 ] (2), [MeHDecIm][ReO 4 ] (3), and [MeBn F Im][ReO 4 ] (4) (Bn = benzyl, Me = methyl, HDec = hexadecyl, Bn F = 2,3,4,5,6-pentafluorobenzyl, and Im = imidazolium).

The initial evaluation of the hazard potential of MTO shows that it causes strong short-term (eco)toxicological effects and offers preliminary indications of its genotoxic potential.

A series of chromophoric Lewis base adducts of methyltrioxorhenium (MTO) was examined. The ligands were pyridine derivatives with different size of the aromatic system and variable substituents, thus providing a variation of electronic and steric parameters. The complexes were fully characterised (UV/Vis, IR and NMR spectroscopy, single-crystal X-ray diffraction and elemental analysis) and their stability constants in dichloromethane were determined by means of UV/Vis spectroscopy. Moreover, this report presents a study of the influence of these N-donor ligands coordinated to MTO on the catalytic activity of epoxidation of 1-octene.