Fluoride, bifluoride and trifluoromethyl complexes of iridium(<scp>i</scp>) and rhodium(<scp>i</scp>)

Truscott, Byron J.; Nahra, Fady; Slawin, Alexandra M. Z.; Cordes, David B.; Nolan, Steven P.

doi:10.1039/c4cc07772e

Cited by 16 publications

(10 citation statements)

References 70 publications

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“…Similarly, the Ir–C carbene bond lengths of 2.018(5), 2.026(3), and 2.029(5) Å for 1i – 3i , respectively, are shorter than the sum of the individual covalent radii of the iridium and carbon atoms [ d (Ir–C) = 2.172 Å] and comparable to those of other structurally characterized examples such as (1,3‐diisopropylbenzimidazol‐2‐ylidene)Ir(COD)Cl [ d (Ir–C carbene ) = 2.020(4) Å] and (1,3‐diisopropyl‐1,3‐dihydro‐2 H ‐imidazol‐2‐ylidene)Ir(COD)F [ d (Ir–C carbene ) = 2.014(3) Å] …”

Section: Resultssupporting

confidence: 64%

“…Of particular interest are the M–C carbene bond lengths in the rhodium and iridium complexes. The Rh–C carbene bond lengths of 2.020(18), 2.023(4), and 2.019(4) Å for 1h – 3h , respectively, are slightly shorter than the sum of the covalent radii of the individual atoms [ d (Rh–C) = 2.182 Å] but are comparable to those of structurally characterized examples such as (1‐isopropyl‐3‐phenylbenzimidazol‐2‐ylidene)Rh(COD)Cl [ d (Rh–C carbene ) = 2.015(9) Å] and (1,3‐dicyclohexyl‐1,3‐dihydro‐2 H ‐imidazol‐2‐ylidene)Rh(COD)F [ d (Rh–C carbene ) = 2.022(3) Å] …”

Section: Resultsmentioning

confidence: 78%

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Chiral Oxazolidine‐Fused N‐Heterocyclic Carbene Complexes of Rhodium and Iridium and Their Utility in the Asymmetric Transfer Hydrogenation of Ketones

2017

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The catalytic potential of new N-heterocyclic carbene ligands, derived from a chiral fused bicyclic ring scaffold with restricted rotation along the C-N bond bearing the chiral auxiliary, has been explored in the transition-metal-mediated asymmetric transfer hydrogenation reactions of ketones. In particular, the chiral oxazolidine-fused N-heterocyclic carbene precursors (3S)-3-R-6-methyl-7-phenyl-2,3-dihydroimidazo[5,1-b]oxazol-6-ium iodide [R = sec-butyl (1f ), i-butyl (2f ), isopropyl (3f )] were synthesized from commercially available optically pure amino acids in a multistep sequence that avoids tedious chiral resolution. The reactions of the chiral imidazolium iodide salts 1f-3f with Ag 2 O yielded the corresponding silver complexes [a]

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Section: Resultssupporting

confidence: 64%

Section: Resultsmentioning

confidence: 78%

Chiral Oxazolidine‐Fused N‐Heterocyclic Carbene Complexes of Rhodium and Iridium and Their Utility in the Asymmetric Transfer Hydrogenation of Ketones

2017

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“…Recently, Nolan and co-workers also reported the synthesis of several NHC-based Ir I and Rh I fluoride and bifluoride complexes (Scheme 18) [97]. Using the same strategy described above, a metal hydroxide of the type [M(OH)(cod)(NHC)] (M = Rh, Ir) afforded the corresponding bifluorides 22-24 in good yields (93%, 90% and 82%, respectively).…”

Section: Iridium and Rhodiummentioning

confidence: 97%

“…A summary of the methods used is shown in Scheme 22. The Nolan group also applied the same strategy on NHC-based bifluoride complexes of Iridium and rhodium [97]. M a n u s c r i p t…”

Section: Analysis and Outlookmentioning

confidence: 99%

Transition metal bifluorides

Nahra

Brill

Gómez‐Herrera

et al. 2016

Coordination Chemistry Reviews

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A c c e p t e d M a n u s c r i p t HighlightsSince their discovery four decades ago, transition metal bifluoride complexes have long been considered as unwanted byproducts, a necessary evil, on the route to access fluoride complexes. Until recently, reports on this chemistry almost always presented these complexes as a fluke discovery. However, with the recent increase in reports and applications involving such species, a renewed interest in these complexes has been observed. Most of the work done in this area, so far, has been directed toward the synthesis and quite challenging characterization of these complexes, yet mostly neglecting the behavior of such species and their influence on catalytic processes. The aim of this work is to present a summary of the various preparation methods, characterization techniques and applications of reported transition metal bifluoride complexes. It is our hope that by centralizing all information available on such species, future efforts aimed at exploiting the full potential of transition metal bifluoride species can be facilitated.

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“…stoichiometric ratios used for these reactions. In the same contribution, the first Ir-CF 3 complexes featuring NHC ligands (78) were synthesized using in situ prepared AgCF 3 as a transfer agent (Scheme 36). The method was not general in scope of the NHC ligands that could be used.…”

Section: Metal-free Carbene Transfer Agents For the Synthesis Of Nhc-mentioning

confidence: 99%

Iridium complexes with monodentate N-heterocyclic carbene ligands

Sipos

Dorta

2018

Coordination Chemistry Reviews

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the stoichiometry, both [(IMes)Ir(COE)(N 2)Cl] and [(IMes) 2 Ir(COE)Cl] (198 in Scheme 75) were successfully isolated. 44 Finally, as Scheme 20 in Section 4.4 shows, a series of stable (NHC) 2 Ir(COE)Cl complexes were isolated either by the free carbene or the silver transmetallation method. Scheme 7. The synthesis of half-sandwich NHC-Ir(III) 24. The most commonly used precursor for the synthesis of NHC-Ir(III) complexes is [Cp*IrCl 2 ] 2. In 2000, Herrmann showed that treatment of [Cp*IrCl 2 ] 2 with 1 equivalent of ICy per iridium yielded 24 in an excellent 90% yield (Scheme 7). 45 Termaten et al. employed the same procedure for the synthesis of (IiPr Me)Ir(Cp*)Cl 2 (26a in Scheme 8). 15 An alternative synthetic route to access free NHCs was described in 1993 by Kuhn and Kratz, who prepared free carbenes via the reduction of thiones 25 by metallic potassium in THF (Scheme 8). 46 Using this method, Yamaguchi and coworkers prepared 26a-c by cannulating the solution of the in situ generated NHCs to a solution of [Cp*IrCl 2 ] 2 in THF (Scheme 8). 47 Scheme 8. Synthesis of NHC-Ir(III) from free carbenes. 4.2. Alkoxy metal precursors and base-assisted one-pot methods It was Köcher and Herrmann who first developed a one pot procedure in which [Ir(COD)(µ-OEt)] 2 was prepared in situ by reacting [Ir(COD)Cl] 2 with four equivalents of NaOEt. Subsequently, four equivalents of 1,3-bis(diphenylmethyl)imidazolium bromide were added and the air and moisture stable 27 was isolated two days later (Scheme 9). 48 Interestingly, despite the fact that a large excess of the NHC salt was employed, formation of a cationic biscarbene complex was not observed. Scheme 9. NHC-Ir complex synthesis from an in situ generated metal-alkoxide. The procedure starting with the alkoxy metal precursor gave bis-NHC substituted complexes (28) when sterically less demanding NHC salts were applied (Scheme 10). Notably, even a 2.2:1 ratio of NHC:Ir was sufficient to isolate 28a-c in good yields (67-86%). Iridium and rhodium bis-NHC complexes with chelating N-N bridged NHCs were prepared in the same way. 39 Scheme 10. Cationic biscarbene complexes. Recently, Savka and Plenio described a one-step synthesis to access (NHC)M(COD)Cl (M = Rh, Ir) as well as (NHC)M(CO) 2 Cl complexes by employing a relatively weak base (K 2 CO 3) in acetone under air (Scheme 11). 49 Scheme 11. One pot synthesis of (NHC)Ir(COD)Cl and (NHC)Ir(CO) 2 Cl complexes. 4.3. The silver transmetallation method Scheme 12. The silver transmetallation method. The silver transmetallation method for the synthesis of NHC-iridium complexes was first published by Crabtree and coworkers. 50 The NHC-silver adducts (29) were generated in excellent yields by modifying the original procedure of Wang and Lin. 51 Subsequent treatment of [Ir(COD)Cl] 2 at room temperature gave 30a and 30b in 81 and 68% yield, respectively (Scheme 12). X-ray analysis of the yellow crystals of 30a revealed square planar geometry around the iridium center. Complexes 30 smoothly reacted with CO to form bis-carbonyl compound...

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Fluoride, bifluoride and trifluoromethyl complexes of iridium(i) and rhodium(i)

Abstract: New methods for the preparation of a range of NHC-based Ir(i) and Rh(i) fluoride, bifluoride and trifluoromethyl complexes are reported.

Cited by 16 publications

References 70 publications

Chiral Oxazolidine‐Fused N‐Heterocyclic Carbene Complexes of Rhodium and Iridium and Their Utility in the Asymmetric Transfer Hydrogenation of Ketones

Chiral Oxazolidine‐Fused N‐Heterocyclic Carbene Complexes of Rhodium and Iridium and Their Utility in the Asymmetric Transfer Hydrogenation of Ketones

Transition metal bifluorides

Iridium complexes with monodentate N-heterocyclic carbene ligands

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