Heating the six-membered ring N-heterocyclic carbenes 6-Me and 6-Et with Rh(PPh3)4H afforded the rhodium monocarbene hydride complexes Rh(6-NHC)(PPh3)2H as a mixture of cis- and trans-P,P isomers (4a/b, NHC = 6-Me; ratio = 1:20; 5a/b, NHC = 6-Et; ratio = 1:9). Reaction of 4a/b with Et3N·3HF gave only the trans-P,P isomer of the bifluoride complex Rh(6-Me)(PPh3)2(FHF) (6b), whereas 5a/b reacted to form Rh(6-Et)(PPh3)2(FHF) as a mixture of cis- and trans-phosphine isomers (7a/b). Variable temperature 1H and 19F NMR spectroscopy showed that 6b and the previously reported 6-iPr carbene analogue cis-Rh(6-iPr)(PPh3)2(FHF) (2a; Organometallics2012418584) were fluxional in solution. 19F Magnetization transfer experiments revealed F exchange in both compounds and afforded similar ΔH ⧧ values (2a, 51 ± 5 kJ mol–1; 6b, 60 ± 6 kJ mol–1) but somewhat different values of ΔS ⧧ (2a, −70 ± 17 J mol–1 K–1; 6b, −27 ± 18 J mol–1 K–1). The fluoride complexes cis-Rh(6-Me)(PPh3)2F (8a), cis-/trans-Rh(6-Et)(PPh3)2F (9a/b), and the previously reported 6-iPr analogue 3a could be formed upon C–F activation of CF3CFCF2 by 4a/b, 5a/b, and Rh(6-iPr)(PPh3)2H (1a/b), respectively. Complex 3a reacted slowly with H2 to partially reform 1a/b but rapidly with CO to give Rh(6-iPr)(PPh3)(CO)F (10) and Rh(PPh3)2(CO)F, and also quickly with Me3SiCF3 to form cis-Rh(6-iPr)(PPh3)2(CF3) (11a). Complexes 4b, 5b, 6b, 7b, and 11a were structurally characterized.

Both [Ru(cod)Cl 2 ] n and [Ru(PPh 3 ) 3 Cl 2 ] react with the N-iPr substituted N-heterocyclic carbene IiPr 2 Me 2 [1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene] at elevated temperature to give the cyclometallated triscarbene product [Ru-(IiPr 2 Me 2 )Ј(IiPr 2 Me 2 ) 2 Cl] (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 ) 3 Cl 2 ] affords the cyclometallated monocarbene complex [Ru(ItBu 2 )Ј(PPh 3 ) 2 Cl] (2). Cyclo-[a] 2213 metallation of the N-ethyl derivative IEt 2 Me 2 [1,3-diethyl-4,5-dimethylimidazol-2-ylidene] takes place upon heating with [Ru(DMSO) 4 Cl 2 ] to give the tris-DMSO product, [Ru-(IEt 2 Me 2 )Ј(DMSO) 3 Cl] (3), which undergoes substitution of the S-bound DMSO ligands in the presence of CO and PPh 3 to yield [Ru(IEt 2 Me 2 )Ј(CO) 3 Cl] (4) and [Ru(IEt 2 Me 2 )Ј(PPh 3 ) 2 -Cl] (6). In contrast, IEt 2 Me 2 reacts with [Ru(PPh 3 ) 3 Cl 2 ] to give [Ru(IEt 2 Me 2 ) 4 Cl 2 ] (7). The molecular structures of compounds 1-4, 6 and 7 have been determined.hydrido halido precursors. [6] For the RuHX species (X = F, Cl), the NHC acts not only as a ligand, but also as a base to facilitate the elimination of HX. [7] In light of the research by Wolf, Radius and others, we turned our attention to ruthenium dichlorido starting materials and now report the use of [Ru(cod)Cl 2 ] n , [Ru(PPh 3 ) 3 Cl 2 ] as well as [Ru(DMSO) 4 -Cl 2 ] to afford a range of new cyclometallated Ru N-alkyl NHC complexes.