Heterobimetallic carbene and allenylidene complexes; syntheses and crystal structures of iron(II)–chromium(&gt;0&gt;) cycloheptatrienylidene and (cycloheptatrienylidene)ethenylidene complexes †

Tamm, Matthias; Grzegorzewski, Alexander; Brüdgam, Irene; Hartl, Hans

doi:10.1039/a806368k

Cited by 16 publications

(13 citation statements)

References 43 publications

(26 reference statements)

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“…This has been explained in terms of a larger contribution from the alkynyl-type resonance form II as opposed to the genuine cumulenylidene-type resonance form I (Scheme 2) when the metal center is more electron-rich and the substituents at C-γ are less able to support a positive charge adjacent to them. [1,2,4,20,21] In the light of the stability of the ferrocenylmethylene carbenium ion [22] the ferrocenyl substituent may be expected to stabilize the alternative alkynyl resonance form III, as indicated in Scheme 2, in line with the results from IR spectroscopy. We note here that Le Bozec et al arrived at a similar conclusion in their study of [(C 6 Me 6 )-Cl(PMe 3 )RuϭCϭCϭC(Ph)(Fc)] ϩ PF 6 Ϫ , closely related to 3a and 3b.…”

Section: Synthesis Molecular Structures and Spectroscopic Propertiesmentioning

confidence: 84%

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

et al. 2003

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, L 2 = 2 PPh 3 or 1,1Ј-bis(diphenylphosphanyl)ferrocene (dppf), R = Ph or ferrocenyl] and their spectroscopic and electrochemical characteristics. Three of these compounds possess redox-active, ferrocenebased substituents or ligands − that are oxidized at lower potentials than the ruthenium center itself − attached either to the terminal carbon atom of the allenylidene ligand or to the ruthenium atom. The Fc/Ph-substituted complexes 3a and 3b provide unique examples of hindered rotation of the allenylidene substituent around the M=C bond. For 3a (L 2 = 2 PPh 3 ), two isomers differing in the orientation of the vertically aligned, unsymmetrically substituted allenylidene ligand are discernible even at 388 K. The dppf-substituted congener 3b has the allenylidene ligand in a horizontal orientation and exhibits a rotational barrier, as determined by dynamic 31 P NMR spectroscopy, of ∆G ϶ = 47 kJ/mol at T C = 238 K. The changes in the spectroscopic and electrochemical properties upon replacement of the PPh 3 by a dppf ligand and the Ph by an Fc moiety can be explained in terms of the bonding within these systems. These effects are attenuated when the ferrocene-based redox tags are oxidized, as shown by IR and

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Section: Synthesis Molecular Structures and Spectroscopic Propertiesmentioning

confidence: 84%

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

et al. 2003

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“…However, these are strongly polarized toward the alkynyl resonance forms, with the tropylium group offering further η-bonding capacity (Scheme ). , The use of cycloheptatriene as an ancillary ligand in organometallic chemistry is of course well documented, with a wealth of cycloheptatrienyl half-sandwich complexes having been synthesized and studied. , …”

Section: Resultsmentioning

confidence: 99%

“…However, these are strongly polarized toward the alkynyl resonance forms, with the tropylium group offering further η-bonding capacity (Scheme 11). 24,25 The use of cycloheptatriene as an ancillary ligand in organometallic chemistry is of course well documented, with a wealth of cycloheptatrienyl half-sandwich complexes having been synthesized and studied. 26,27 Reactions of 3b,d and 4b,d with the tropylium salt [C 7 H 7 ]BF 4 were therefore undertaken to further explore the breadth of the electrophilic addition chemistry (Scheme 12).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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

et al. 2020

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The methyl substituents in the cationic allenylidene complexes trans-[Ru{CCC(Me)R}Cl(dppe) 2 ]OTf ([1a−f]OTf) are readily deprotonated to give the corresponding alkenyl acetylide complexes trans-[Ru{CCC(CH 2 )R}Cl(dppe) 2 ] (3; R = Me (a), Ph (b), c C 5 H 10 (c), 4-MeS-C 6 H 4 (d), c C 4 H 3 S (e), c C 5 H 4 N (f)). Similar chemistry is also observed from [Ru{CCC(Me)Ph}(dppe)Cp*]-PF 6 ([2b]PF 6 ) and [Ru{CCC(Me)(4-MeS-C 6 H 4 )}(dppe)Cp*]-PF 6 ([2b]PF 6 ), chosen to broaden the reaction scope, giving [Ru{C CC(CH 2 )Ph}(dppe)Cp*] (4b) and [Ru{CCC(CH 2 )(4-MeS-C 6 H 4 )}(dppe)Cp*] (4d). In turn, reactions of 3b,d and 4b,d with the [BF 4 ] − salt of the electrophilic tritylium [CPh 3 ] + cation give the functionalized allenylidene complexes trans-[Ru{CCC(CH 2 CPh 3 )-R}Cl(dppe) 2 ]BF 4 ([5b,d]BF 4 ) and [Ru{CCC(CH 2 CPh 3 )R}(dppe)Cp*]BF 4 ([6b,d]BF 4 ) formed by addition of the electrophile to the remote vinylic carbon (C(δ)). Although trans-[Ru{CCC(CH 2 CPh 3 )Me}Cl(dppe) 2 ]BF 4 ([5a]BF 4 ) could not be successfully purified from reactions of 3a with [CPh 3 ]BF 4 , deprotonation of the crude product gave the Zaitsev vinyl product trans-[Ru{CCC(CHCPh 3 )Me}Cl(dppe) 2 ] (7a) in good yield. The initial cycloheptatrienyl adducts formed from reactions of 3b,d and 4b,d with the tropylium salt [C 7 H 7 ]BF 4 undergo a ring-contraction process in chloroform solutions upon exposure to air, to give the styrene-like products trans-[Ru{CCC(R)C(H)CHPh}Cl(dppe) 2 ]BF 4 ([10b,d]BF 4 ) and [Ru{CC C(R)C(H)CHPh}(dppe)Cp*]BF 4 ([11b,d]BF 4 ), through what is believed to be a radical mechanism mediated by triplet oxygen.

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“…In the presence of sodium hydroxide, alkyne 2 reacts with Ph 3 PAuCl in methanol, affording the gold–acetylide complex 3 in 84% yield. Lastly, a hydride abstraction 15 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), followed by anion exchange with HBF 4 , led to the cationic allenylidene gold complex 4 as a white solid, but in only 37% yield. Moreover, this complex appeared to decompose rapidly in solution ( vide infra ).…”

Section: Resultsmentioning

confidence: 99%