Neutral and Cationic Hydridoruthenium Tetrakiscarbene Complexes

Wolf R, Plois M, Hepp A

Abstract

Starting from the novel chlorido precursor trans-[RuCl2(IMe)4] (1, IMe = 1,3,4,5-tetramethylimidazol-2-ylidene), hydridoruthenium complexes trans-[RuH2(IMe)4] (2) and [RuH(IMe)4][BEt4] (3BEt4) have been synthesized. Complex 2 was isolated from the reaction of I with LiAlH4, while ionic compound 3 was obtained when LiBHEt3 was used as the hydride source. Complexes 1-3 have been characterized by Xray crystallography, multinuclear NMR, IR, UV/Vis spectroscopy and mass spectrometry. Neutral dihydride 2 displays a tetragonal bipyramidal geometry with four carbene groups coordinated to ruthenium in equatorial positions and two apical hydrogen atoms. DFT calculations Suggest that the trans structure observed for 2 is preferred over a cis arrangement for steric reasons. The ruthenium atom of 3 has a tetragonal pyramidal coordination environment with a vacant coordination site sterically protected by the Me substituents of the ligands. Thus, compound 3 should be an attractive target for future coordination studies.