Neutral and Cationic Hydridoruthenium Tetrakiscarbene Complexes

Starting from the novel chlorido precursor trans ‐[RuCl 2 (IMe) 4 ] ( 1 , IMe = 1,3,4,5‐tetramethylimidazol‐2‐ylidene), hydridoruthenium complexes trans ‐[RuH 2 (IMe) 4 ] ( 2 ) and [RuH(IMe) 4 ][BEt 4 ] ( 3 BEt 4 ) have been synthesized. Complex 2 was isolated from the reaction of 1 with LiAlH 4 , while ionic compound 3 was obtained when LiBHEt 3 was used as the hydride source. Complexes 1 – 3 have been characterized by X‐ray 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.