Formation of Cyclometallated N‐Heterocyclic Carbene (NHC) Complexes from L_nRuCl₂ (L = Cyclooctadiene, PPh₃, DMSO) Precursors

Abstract

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.

Intramolecular C–H Activation Reactions of Ru(NHC) Complexes Combined with H2 Transfer to Alkenes: A Theoretical Elucidation of Mechanisms and Effects of Ligands on Reactivities

“…The N , N ′-diisopropyl NHC (I i Pr 2 Me 2 ) in complex 1 is more reactive than the N , N ′-diethyl ligand (IEt 2 Me 2 ) . Similar alkene hydrogenation reactions were later reported with ruthenium monohydride monochloride complex 2 (Figure b). , …”

N‐Heterocyclic Gallylene Supported Organoruthenium Derivatives – Synthesis, Structure, and C–H Bond Cleavage

“…The HMBC and 1 H– 1 H‐COSY spectra of 6 point to the presence of two different diastereotopic protons (Ru–CH 2 ) as broad and weak signals at δ = 3.05 and 1.57 ppm ( 3 J H,H = 13.1 Hz). The corresponding 13 C NMR signal of this carbon atom is found at δ = 23.4 ppm, which is similar to those of other ruthenium complexes such as the products resulting from C–H activation of NHC25 or phosphane‐supported ruthenium complexes, for example, RuCl 2 [(2,6‐Me 2 C 6 H 3 )PPh 2 ] 2 ( δ = 3.81 to 3.37 ppm) 26a. The 1 H NMR also shows the existence of an N–H proton at δ = 6.48 ppm as a broad signal.…”

“…The Ru–C bond length [Ru(1)–C(30), 2.209(3) Å] is similar to those in orthometallated ruthenium complexes containing Ru–C single bonds. The Ru–C distance in 6 is slightly longer than those in NHC or phosphane‐supported ruthenium complexes such as [Ru(IEt 2 Me 2 )(DMSO) 3 Cl] [2.130(2) Å, IEt 2 Me 2 = 1,3‐diethyl‐4,5‐dimethylimidazol‐2‐ylidene, DMSO = dimethyl sulfoxide], [Ru(IEt 2 Me 2 )(CO) 3 Cl] [2.1656(17) Å],25 and [RuCl{(2‐CH 2 ‐6‐MeC 6 H 3 )PPh 2 }(CO)(2,6‐Me 2 C 6 H 3 )PPh 2 ] [2.043(8) Å] 26. Furthermore, the Ru(1)– p ‐cymene centroid distance is 1.722 Å, which is very close to that in similar GaCp*‐supported complexes, for example, [(η 6 ‐p ‐cymene)Ru(GaCp*) 2 GaCl 3 ] (1.742 Å) 21.…”

Iridium Complexes of the Conformationally Rigid IBioxMe4 Ligand: Hydride Complexes and Dehydrogenation of Cyclooctene

“…With the aim of investigating low-coordinate NHC complexes of rhodium and iridium, we have recently begun to expand the coordination chemistry of IBiox ligands, seeking to exploit their conformational rigidity to avoid intramolecular cyclometalation reactions that can occur via C–H bond activation of the downward pointing alkyl and aryl NHC appendages. , In particular, we have focused our efforts on IBioxMe 4 , which shares many structural similarities with the commonly employed I t Bu ligand that has been shown to undergo cyclometalation reactions when partnered with reactive late transition metal fragments (Scheme ). , …”