Further Chemistry of Ruthenium Alkenyl Acetylide Complexes: Routes to Allenylidene Complexes via a Series of Electrophilic Addition Reactions

Hall, Michael R.; Korb, Marcus; Moggach, Stephen A.; Low, Paul J.

doi:10.1021/acs.organomet.0c00371

Cited by 8 publications

(32 citation statements)

References 51 publications

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“…In contrast to the reactions of 3 a – d described above, treatment of 3 e with HBF 4 ⋅ Et 2 O resulted in the formation of a 1 : 1 product mixture likely corresponding to allenylidene‐acetylide [ 2 e ] + and vinylvinylidene‐acetylide [ 2 e' ] + products (Scheme 9), evidenced by 31 P{ 1 H} resonances at 40.24 and 40.05 ppm and accompanying vinylidene ν(C=C) and allenylidene ν(C=C=C) IR bands at 1625 and 1957 cm −1 respectively. This is in accordance with Selegue's observed allenylidene/vinylvinylidene formation equilibria from the protonation of enynyl complexes containing cyclic terminal substituents, [33a] as well as more recent observations from our group [23] …”

Section: Resultssupporting

confidence: 93%

“…Although aerial oxidation of organic alkenes to carbonyls is uncommon, the presence of the ruthenium centre may serve to enhance the electron density in the alkene substituent and accelerate this reaction. This increase in reactivity for alkenylacetylides has been explored previously for a range of reactive outcomes at C(δ), such as protonation [33] or the addition of carbon‐based electrophiles, [23] allowing for the formation of functionalised allenylidene complexes or self‐coupled diruthenum vinylidene‐alkylidene species such as those previously reported by Selegue [34] …”

Section: Resultsmentioning

confidence: 96%

“…In the case of reaction of 1 e with E , the formation of 3 e could be considered to follow an analogous pathway to that proposed for the synthesis of 1 e [23] . The Selegue‐style reaction of propargylic alcohols featuring terminal cyclic substituents afford product mixtures of γ‐hydroxyvinylidene and γ‐vinylvinylidene upon tele‐elimination of water, whilst in each case subsequent deprotonation results in the formation of the desired enynyl ligands and complex 3 e (Scheme 9).…”

Section: Resultsmentioning

confidence: 97%

“…The ready formation of allenylidene complexes [Ru{C=C=C(Me)R}(dppe)Cp*]BF 4 and trans ‐[Ru{C=C=C(Me)R}Cl(dppe) 2 ]BF 4 from treatment of [Ru{C≡CC(=CH 2 )R}(dppe)Cp*] or trans ‐[Ru{C≡CC(=CH 2 )R}Cl(dppe) 2 ] with HBF 4 ⋅ Et 2 O (c.f. Scheme 5) [23,33b] prompts consideration of the use of bis(alkenylacetylide) complexes as entry points to bis(allenylidene) systems (Scheme 14). The reactions of yellow to orange solutions of 3 a – d in CH 2 Cl 2 with HBF 4 ⋅ Et 2 O resulted in the formation of deep blue solutions, with unlocked 31 P{ 1 H} NMR measurements showing the formation of a transient species at approximately 42.0 ppm, accompanied by strong IR ν(C=C=C) bands at ca.…”

Section: Resultsmentioning

confidence: 99%

“…In searching for a more general route to bis(allenylidene) complexes suited for a wider range of terminal substituents and allowing simple access of C 2 ‐symmetric bis(cumulene) species, our attention has been drawn to the recent demonstration of the reversible protonation equilibria of alkenyl acetylide and allenylidene complexes (Scheme 5). [23] The facile interconversion between π‐electron withdrawing allenylidene and strongly σ‐donating/modestly π‐donating acetylide functionalities permits a degree of control over the electronic structure of the ruthenium centre, with the lability of the chloride ligand tuned by this interconversion due to the different trans ‐effect of the acetylide and allenylidene ligands. In seeking to explore conjugated carbon‐rich ligand frameworks, this activation/deactivation of the chloride ligand to substitution reactions with the nature of the trans ‐ligand, as well as the allenylidene/alkenylacetylide protonation equilibria permits wide scope for the formation of allenylidene and acetylide ligand set combinations.…”

Section: Introductionmentioning

confidence: 99%

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Syntheses and Structures of trans‐bis(Alkenylacetylide) Ruthenium Complexes

Hall

Moggach

Low

2021

Chemistry An Asian Journal

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A series of ruthenium alkenylacetylide complexes trans‐[Ru{C≡CC(=CH2)R}Cl(dppe)2] (R=Ph (1 a), cC4H3S (1 b), 4‐MeS‐C6H4 (1 c), 3,3‐dimethyl‐2,3‐dihydrobenzo[b]thiophene (DMBT) (1 d)) or trans‐[Ru{C≡C‐cC6H9}Cl(dppe)2] (1 e) were allowed to react with the corresponding propargylic alcohol HC≡CC(Me)R(OH) (R=Ph (A), cC4H3S (B), 4‐MeS‐C6H4 (C), DMBT (D) or HC≡C‐cC6H10(OH) (E) in the presence of TlBF4 and DBU to presumably give alkenylacetylide/allenylidene intermediates trans‐[Ru{C≡CC(=CH2)R}{C=C=C(Me)}(dppe)2]PF6 ([2]PF6). These complexes were not isolated but deprotonated to give the isolable bis(alkenylacetylide) complexes trans‐[Ru{C≡CC(=CH2)R}2(dppe)2] (R=Ph (3 a), cC4H3S (3 b), 4‐MeS‐C6H4 (3 c), DMBT (3 d)) and trans‐[Ru{C≡C‐cC6H9}2(dppe)2] (3 e). Analogous reactions of trans‐[Ru(CH3)2(dmpe)2], featuring the more electron‐donating 1,2‐bis(dimethylphosphino)ethane (dmpe) ancillary ligands, with the propargylic alcohols A or C and NH4PF6 in methanol allowed isolation of the intermediate mixed alkenylacetylide/allenylidene complexes trans‐[Ru{C≡CC(=CH2)R}{C=C=C(Me)}(dmpe)2]PF6 (R=Ph ([4 a]PF6), 4‐MeS‐C6H4 ([4 c]PF6). Deprotonation of [4 a]PF6 or [4 c]PF6 gave the symmetric bis(alkenylacetylide) complexes trans‐[Ru{C≡CC(=CH2)R}2(dmpe)2] (R=Ph (5 a), 4‐MeS‐C6H4 (5 c)), the first of their kind containing the dmpe ancillary ligand sphere. Attempts to isolate bis(allenylidene) complexes [Ru{C=C=C(Me)R}2(PP)2]2+ (PP=dppe, dmpe) from treatment of the bis(alkenylacetylide) species 3 or 5 with HBF4 ⋅ Et2O were ultimately unsuccessful.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Syntheses and Structures of trans‐bis(Alkenylacetylide) Ruthenium Complexes

Hall

Moggach

Low

2021

Chemistry An Asian Journal

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Quantification of the Helicality of Helical Molecular Orbitals

2021

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The frontier molecular orbital (MO) topology of linear carbon molecules, such as polyynes, can be visually identified as helices. However, there is no clear way to quantify the helical curvature of these π-MOs, and it is thus challenging to quantify correlations between the helical curvature and molecular properties. In this paper, we develop a method that enables us to compute the helical curvature of MOs based on their nodal planes. Using this method, we define a robust way of quantifying the helical nature of MOs (helicality) by their deviation from a perfect helix. We explore several limiting cases, including polyynes, metallacumulenes, cyclic allenes, and spiroconjugated systems, where the change in helical curvature is subtle yet clearly highlighted with this method. For example, we show that strain only has a minor effect on the helicality of the frontier orbitals of cycloallenes and that the MOs of spiroconjugated systems are close to perfect helices around the spiro-carbon. Our work provides a well-defined method for assessing orbital helicality beyond visual inspection of MO isosurfaces, thus paving the way for future studies of how the helicality of π-MOs affects molecular properties.

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Oxidative Coupling of Ruthenium Alkenyl Acetylide Complexes as a Route to Dinuclear Complexes Featuring Carbon-Rich Bridging Ligands

et al. 2022

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Reaction of [RuCl(dppe)Cp*] with the propargylic alcohols HC�CC(OH)(R)Me [R = Ph (A), 4-pyridyl (B), and 4-NO 2 -C 6 H 4 (C)] in the presence of NH 4 PF 6 in MeOH, followed by treatment with base (t-BuOK) and workup under air, resulted in the unanticipated formation of the dinuclear bis(acetylide) species [{Ru(dppe)Cp*} 2 {μ-C�CC(R)�HC−CH�C(R)C�C}] [R = Ph (2a), 4-py (2b), 4-NO 2 -C 6 H 4 (2c)]. The dimeric complexes 2 containing an octa-3,5-diene-1,7-diyndiyl bridging ligand are formed through a sequence of reactions involving formation of the methyl allenylidene complexes [Ru{C�C�C(R)Me}(dppe)-Cp*] + and deprotonation to give the transient alkenylacetylide species [Ru{C�CC(R)�CH 2 }(dppe)Cp*] (1). Oxidation of 1 affords the radical cation [1] + , which homocouples to give the dimeric ethane-bridged bis(allenylidene) [{Ru(dppe)Cp*} 2 {μ-C� C�C(R)CH 2 −CH 2 C(R)�C�C}] 2+ [(2-H 2 ) 2+ ] and is deprotonated to give 2. Examples of these various intermediates have been spectroscopically observed and isolated through stoichiometric reactions and the reaction pathway mapped by in situ electrochemical (cyclic voltammetry, CV) and infrared-spectroelectrochemical (IR-SEC) measurements. The bimetallic complexes 2a−c each undergo two sequential oxidation events at low potentials, giving species characterized by IR-SEC as a strongly delocalized mixed-valence radical cations [2a−c] + and the dicationic bis(allenylidene) species [{Ru(dppe)Cp*} 2 {μ-C�C�C(R)− HC�CH−C(R)�C�C}] 2+ [(2a−c) 2+ ]. Chemical oxidation of 2a with one or two equivalents of [FeCp 2 ]PF 6 allowed for isolation of the monocation [2a]PF 6 and dication [2a][PF 6 ] 2 , respectively.

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Further Chemistry of Ruthenium Alkenyl Acetylide Complexes: Routes to Allenylidene Complexes via a Series of Electrophilic Addition Reactions

Cited by 8 publications

References 51 publications

Syntheses and Structures of trans‐bis(Alkenylacetylide) Ruthenium Complexes

Syntheses and Structures of trans‐bis(Alkenylacetylide) Ruthenium Complexes

Quantification of the Helicality of Helical Molecular Orbitals

Oxidative Coupling of Ruthenium Alkenyl Acetylide Complexes as a Route to Dinuclear Complexes Featuring Carbon-Rich Bridging Ligands

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