Neutral and Cationic Hydridoruthenium Tetrakiscarbene Complexes

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 1 with LiAlH4, while ionic compound 3 was obtained when LiBHEt3 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.

Formation of Cyclometallated N‐Heterocyclic Carbene (NHC) Complexes from LnRuCl2 (L = Cyclooctadiene, PPh3, DMSO) Precursors

“…Literature methods (or modifications thereof) were used for the synthesis of ItBu 2 , [15] IiPr 2 Me 2 , [16] IEt 2 Me 2 , [16] [Ru(cod)Cl 2 ] n , [17] [Ru(PPh 3 ) 3 Cl 2 ] [18] and [Ru(DMSO) 4 Cl 2 ]. [19] [Ru(IiPr 2 Me 2 )Ј(IiPr 2 Me 2 ) 2 (100 mg, 0.21 mmol) and IEt 2 Me 2 (94 mg, 0.67 mmol) were charged to an ampoule fitted with a J. Young's PTFE tap, dissolved in toluene (5 mL), and then heated at 373 K for 7 h. The reaction mixture was filtered, and the precipitate washed with hexane (3 ϫ 10 mL) and dried under vacuum to obtain a light brown powder (60 mg, 56 % yield).…”

“…The structure is analogous to the N-Me and N-nPr derivatives reported by Wolf and Radius respectively. [2,3] On the basis of our earlier studies, [7] it is tempting to connect the cyclometallation reactions to the presence of excess amounts of NHC (4-6 equiv.) in all of the reactions.…”

“…We have described the synthesis of a number of cyclometallated Ru-NHC products containing both N-alkyl-and N-aryl-substituted NHCs using ruthenium dihydrido and By employing the same approach used by Wolf and coworkers, [2] reactions of [Ru(cod)Cl 2 ] n with an excess (4 equiv.) of ItBu 2 [1,3-di-tert-butylimidazol-2-ylidene], IEt 2 Me 2 [1,3-diethyl-4,5-dimethylimidazol-2-ylidene] and IiPr 2 Me 2 [1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene] were attempted in toluene solution at 100°C for 4 h. No clean Ru-NHC products could be isolated from the reaction involving the tert-butyl carbene, most likely because of its very bulky nature.…”

Room Temperature Regioselective Catalytic Hydrodefluorination of Fluoroarenes with trans‐[Ru(NHC)4H2] through a Concerted Nucleophilic Ru−H Attack Pathway

“…[12] If KC 8 /H 2 is instead used as the reductant, 3 [12] If KC 8 /H 2 is instead used as the reductant, 3…”

“…The trans-dihydride complex 3 (Scheme 3) was reported previously by Wolf upon reduction of [Ru(IMe 4 ) 4 Cl 2 ]w ith LiAlH 4 ,although it could only be obtained as an impure solid in low yield. [12] If KC 8 /H 2 is instead used as the reductant, 3…”