Arene Hapticity in (C6H6)Cr(CO)n (n = 1−5) Complexes:  A DFT Study of Singlet and Triplet Energy Surfaces

Cohen, Revital; Weitz, Eric; Martin, Jan M. L.; Ratner, Mark A.

doi:10.1021/om034367z

Cited by 25 publications

(24 citation statements)

References 57 publications

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“…To the best of our knowledge, only EHMO calculations of the stability of the hypothetical [(η 2 ‐C 10 H 8 )Cr(CO) 3 L x ] intermediates have been reported 51. The related reaction of the benzene replacement in [(η 6 ‐C 6 H 6 )Cr(CO) 3 ] by CO has been studied by modern DFT methods 53…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺

et al. 2012

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Replacement of the naphthalene ligand in ruthenium complex [CpRu(C 10 H 8 )] + (1) by halide anions readily proceeds at room temperature to give insoluble oligomeric species [CpRuX] n (X = Cl, Br, I). Similar reactions in the presence of mono-or bidentate ligands afford complexes [CpRuL 2 X] where L = CO, P(OMe) 3 , tBuNC; L 2 = dppm, dppe, dppp, bipy, phen, cod, nbd, or 1,4-diphenylbutadiene. Useful catalysts [CpRu(cod)X] were obtained by this method in 70-90 % yields. The structure of [CpRu(cod)I] was determined by Xray diffraction. Reaction of 1 with Brand allyl bromide afforded Ru IV complex [CpRu(η 3 -C 3 H 5 )]Br 2 . Cation 1 also was found to react with azide anion in the presence of bidentate phosphanes to afford [CpRuL 2 N 3 ] (L 2 = dppm, dppe). Reaction of 1 with neutral ligands in the absence of nucleophilic anions proceeded under visible-light irradiation to give cat-[a] A. N. Nesmeyanov Institute of Organoelement Compounds, 481 ionic complexes [CpRuL 3 ] + [L = CO, P(OMe) 3 , P(OEt) 3 , tBuNC] in 80-90 % yields. Complex 1 (2 mol-%) catalyzed cyclotrimerization of dipropargyl Meldrum's acid with various alkynes RCϵCH [R = H, Bu, Hex, Ph, SiMe 3 , (CH 2 ) 4 -CϵCH, (CH 2 ) 3 OH, (CH 2 ) 2 Br, CH 2 OMe, CH 2 OAc, CH 2 NMe-Boc] producing benzene derivatives in 50-85 % yields. According to DFT calculations, the attack of the first ligand (Clor L) is a rate-determining step in the naphthalene replacement in 1. The activation barrier for attack of the Clanion is ca. 10 kcal mol -1 lower in energy than that of the neutral ligands L = CO, MeNC, MeCN, thus providing a rationale for the faster reaction in the presence of halide anions. The barriers for naphthalene replacement in 1 were also found to be ca. 10-15 kcal mol -1 lower in energy than those for the benzene replacement in [CpRu(C 6 H 6 )] + . Scheme 1. Reactions of 1 with neutral 2-electron ligands.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺

et al. 2012

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“…For CpRu(CO)Cl, the triplet state was calculated to be significantly higher in energy (>20 kcal/mol), and for CpMn(CO) 2 , there is experimental evidence that the singlet either is the ground state or is very close in energy to the triplet . Similarly, for BzCr(CO) 2 , previous calculations predict that the energy differences between singlet and triplet spin complexes are not significant . Thus, only singlet complexes were considered in the calculations.…”

Section: Experimental and Theoretical Methodsmentioning

confidence: 99%

Time-Resolved Infrared Spectroscopy Studies of Olefin Binding in Photogenerated CpRu(CO)X (X = Cl, I) Transients

et al. 2012

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The mechanism and energetics of ligand (L) substitution (L = THF, cyclopentene, cyclohexene, cyclooctene) from photogenerated CpRu-(CO)(X)L (X = Cl, I) complexes were studied using time-resolved infrared spectroscopy. The reactions proceed through a dissociative mechanism, and the Ru−L binding enthalpies were estimated. The trend in the bond enthalpies, Ru− (η 2 -cyclooctene) ≈ Ru−(η 2 -cyclopentene) > Ru−(η 2 -cyclohexene), is correlated with the strain energy of the cycloalkene ring. For all ligands investigated, CpRu(CO)(Cl)−L binding enthalpies were lower than those for the analogous CpMn(CO) 2 −L and BzCr(CO) 2 −L complexes. DFT calculations indicate that the lower binding enthalpy for the Ru−L complexes is due to a greater reorganizational energy for the CpRu(CO)Cl fragment as it adopts a configuration suitable for interaction with the ligand. ■ INTRODUCTIONTransition-metal-containing organometallic compounds have been shown to catalyze a variety of organic transformations. 1 Complexes containing the ruthenium metal center are particularly active catalysts in a variety of reactions. For example, many key reactions such as alkene isomerization, hydroformylation, C−H activation of arenes, CO 2 fixation, and others have been successfully catalyzed by derivatives of the Ru 3 (CO) 12 cluster. 2 Other Ru carbonyls such as Ru-(CO) 3 (PR 3 ) 2 have also been used as catalysts for the hydrodesulfurization of benzothiophenes. 3 The hydroformylation of 1-octene by CpRu(CO) 2 Cl has also been reported, and despite its high catalytic activity, there are no mechanistic studies that have been undertaken to identify and study the chemistry of the relevant intermediates. 4 Photoinduced time-resolved infrared spectroscopy is a powerful tool for identifying and studying the reactivity of intermediates that may be formed during a catalytic cycle. 5 A vacant coordination site on a metal complex, necessary for catalytic activity, can be generated by photolytic loss of a ligand. Upon binding of the substrate, the reactivity of the resulting intermediate can be probed with infrared light over a range of time scales. Metal carbonyls tend to be the best candidates for such studies, since photolytic loss of CO often proceeds with high quantum efficiency and the remaining CO's attached to the metal center are ideal infrared tags for probing the temporal profile of the resulting intermediates. This technique is therefore well suited to study the reactions of Ru carbonyl intermediates, given their importance in promoting several catalytic processes.As mentioned above, the reaction of CpRu(CO) 2 Cl with 1-octene in the presence of H 2 /CO leads to hydroformylation of the alkene with high selectivity and yield. 4 The mechanism of the reaction was not determined, although it was found that a key species was most likely the CpRu(CO) 2 H complex, presumably formed upon reaction of the parent compound with H 2 . Since this 18-electron coordinatively saturated hydride complex is unlikely to be the active species, it is reasonable to suggest ...

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“…[43,44] The eight arenetungsten complexes (η 6 -C 6 R 6 )-W(CO) n (R = CH 3 , CF 3 ; n = 3, 2, 1, 0) have now been optimized for comparison of their energies of their global minima with those of the isomeric tris(alkyne)tungsten complexes (R 2 C 2 ) 3 W(CO) n (R = CH 3 , CF 3 ; n = 3, 2, 1, 0). The resulting eight global minimum geometries are shown in the Supporting Information and their total energies with zero-point energy corrections are reported in Table 5.…”

Section: (R 2 C 2 ) 3 W (R = Ch 3 Cf 3 )mentioning

confidence: 99%

Inhibition of Alkyne Cyclotrimerization to Arenes on a Metal Site by Four‐Electron Donation through Simultaneous Sigma and Pi Bonding: The Tris(alkyne)Tungsten Carbonyls

Peng

Xie

et al. 2009

Eur J Inorg Chem

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Reactions of fac‐(CH3CN)3W(CO)3 with the alkynes RC≡CR are known experimentally to give the very stable (RC≡CR)3WL (L = CO or CH3CN) complexes without the complexed alkyne ligands on the tungsten site undergoing cyclotrimerization to the corresponding benzene derivatives C6R6. In order to evaluate the thermodynamics of these systems, the structures and energetics of the tris(alkyne)tungsten carbonyls (RC≡CR)3W(CO)n and the corresponding arenetungsten carbonyls (η6‐C6R6)W(CO)n (R = CH3, CF3; n = 3, 2, 1, 0) have been optimized using density functional theory. The cyclotrimerizations of the alkyne ligands in (RC≡CR)3W(CO)n (n = 3, 2) to a benzene ligand in (η6‐C6R6)W(CO)n are predicted to be very exothermic. However, the corresponding cyclotrimerizations of the alkyne ligands in (RC≡CR)3W(CO) and (RC≡CR)3W to a benzene ligand in (η6‐C6R6)W(CO) and (η6‐C6R6)W, respectively, are predicted to range from nearly thermoneutral (R = CH3) to highly endothermic (R = CF3). This can be related to the bonding mode of the alkyne ligands to the tungsten atom. Alkyne ligands bonded to tungsten as four‐electron donors (with one σ bond and one π bond) are resistant to cyclotrimerization reactions. However, alkyne ligands bonded to tungsten as two‐electron donors through only σ bonding of the C≡C triple bond are reactive towards cyclotrimerization reactions. The CF3 derivatives are found to be less reactive towards cyclotrimerization than the CH3 derivatives. The inhibition of alkyne cyclotrimerization on a metal site by bonding as a four‐electron donor through both σ and π bonding can be related to the fact that known alkyne cyclotrimerization catalysts are generally based on late transition metals of groups 8, 9, and 10, rather than early transition metals such as tungsten.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Arene Hapticity in (C₆H₆)Cr(CO)_n (n = 1−5) Complexes: A DFT Study of Singlet and Triplet Energy Surfaces

Cited by 25 publications

References 57 publications

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺

Time-Resolved Infrared Spectroscopy Studies of Olefin Binding in Photogenerated CpRu(CO)X (X = Cl, I) Transients

Inhibition of Alkyne Cyclotrimerization to Arenes on a Metal Site by Four‐Electron Donation through Simultaneous Sigma and Pi Bonding: The Tris(alkyne)Tungsten Carbonyls

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Arene Hapticity in (C6H6)Cr(CO)n (n = 1−5) Complexes: A DFT Study of Singlet and Triplet Energy Surfaces

Cited by 25 publications

References 57 publications

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C10H8)]+

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C10H8)]+

Time-Resolved Infrared Spectroscopy Studies of Olefin Binding in Photogenerated CpRu(CO)X (X = Cl, I) Transients

Inhibition of Alkyne Cyclotrimerization to Arenes on a Metal Site by Four‐Electron Donation through Simultaneous Sigma and Pi Bonding: The Tris(alkyne)Tungsten Carbonyls

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Arene Hapticity in (C₆H₆)Cr(CO)_n (n = 1−5) Complexes: A DFT Study of Singlet and Triplet Energy Surfaces

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺

Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺