Formation of cyclometallated N-heterocyclic carbene (NHC) complexes from L nRuCl 2 (L = Cyclooctadiene, PPh 3, DMSO) precursors

Both [Ru(cod)Cl 2] n and [Ru(PPh 3) 3Cl 2] react with the N-iPr substituted N-heterocyclic carbene IiPr 2Me 2 [1,3-diisopropyl-4,5-dimethylimidazol-2- ylidene] at elevated temperature to give the cyclometallated triscarbene product [Ru(IiPr 2Me 2)'(IiPr 2Me 2) 2Cl] (1), which also contains an agostically bound NHC ligand. Although [Ru(cod)Cl 2] n fails to react with the bulkier tert-butyl carbene ItBu 2 [1,3-di-tert-butylimidazol-2-ylidene], [Ru(PPh 3) 3Cl 2] affords the cyclometallated monocarbene complex [Ru(ItBu 2)'(PPh 3) 2Cl] (2). Cyclometallation of the N-ethyl derivative IEt 2Me 2 [1,3-diethyl-4,5-dimethylimidazol-2-ylidene] takes place upon heating with [Ru(DMSO) 4Cl 2] to give the tris-DMSO product, [Ru(IEt 2Me 2)'(DMSO) 3Cl] (3), which undergoes substitution of the S-bound DMSO ligands in the presence of CO and PPh 3 to yield [Ru(IEt 2Me 2)'(CO) 3Cl] (4) and [Ru(IEt 2Me 2)'(PPh 3) 2Cl] (6). In contrast, IEt 2Me 2 reacts with [Ru(PPh 3) 3Cl 2] to give [Ru(IEt 2Me 2) 4Cl 2] (7). The molecular structures of compounds 1-4, 6 and 7 have been determined. The dichlorido precursors [Ru(cod)Cl 2] n, [Ru(PPh 3) 3Cl 2] and [Ru(DMSO) 4Cl 2] react with a range of N-alkyl-substituted N-heterocyclic carbenes to form the structurally characterized cyclometallated products [Ru(IiPr 2Me 2)'(IiPr 2Me 2) 2Cl], [Ru(ItBu 2)'(PPh 3) 2Cl] and [Ru(IEt 2Me 2)'(DMSO) 3Cl].