Reaction of 1-aryl-2-methylenecyclopropanes with rhodium(I) complexes leading to ring opening isomerization and π co-ordination of the CC double bond

Osakada, Kohtaro; Takimoto, Hisami; Yamamoto, Takakazu

doi:10.1039/a808906j

Cited by 9 publications

(2 citation statements)

References 30 publications

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“…Population of this orbital via π-backdonation results in increased bond order at this position; thus, the C13–C14 bond contracts here in 4 . In accord with this model, the structural data for 4 compare well with analogous distorted trigonal-bipyramidal [η 4 -butadiene] complexes . Taken together, these data suggest that [Cp*H] stabilizes the low-valent metal center by engaging in π-backbonding similar to other diolefinic ligands known to stabilize rhodium(I) compounds (e.g., 1,5-cyclooctadiene) …”

Section: Results and Discussionsupporting

confidence: 63%

Structural and Electrochemical Consequences of [Cp*] Ligand Protonation

et al. 2017

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There are few examples of the isolation of analogous metal complexes bearing [η-Cp*] and [η-Cp*H] (Cp* = pentamethylcyclopentadienyl) complexes within the same metal/ligand framework, despite the relevance of such structures to catalytic applications. Recently, protonation of Cp*Rh(bpy) (bpy = 2,2'-bipyridyl) has been shown to yield a complex bearing the uncommon [η-Cp*H] ligand, rather than generating a [Rh-H] complex. We now report the purification and isolation of this protonated species, as well as characterization of analogous complexes of 1,10-phenanthroline (phen). Specifically, reaction of Cp*Rh(bpy) or Cp*Rh(phen) with 1 equiv of EtNHBr affords rhodium compounds bearing endo-η-pentamethylcyclopentadiene (η-Cp*H) as a ligand. NMR spectroscopy and single-crystal X-ray diffraction studies confirm protonation of the Cp* ligand, rather than formation of metal hydride complexes. Analysis of new structural data and electronic spectra suggests that phen is significantly reduced in Cp*Rh(phen), similar to the case of Cp*Rh(bpy). Backbonding interactions with olefinic motifs are activated by formation of [η-Cp*H]; protonation of [Cp*] stabilizes the low-valent metal center and results in loss of reduced character on the diimine ligands. In accord with these changes in electronic structure, electrochemical studies reveal a distinct manifold of redox processes that are accessible in the [Cp*H] complexes in comparison with their [Cp*] analogues; these processes suggest new applications in catalysis for the complexes bearing endo-η-Cp*H.

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Section: Results and Discussionsupporting

confidence: 63%

Structural and Electrochemical Consequences of [Cp*] Ligand Protonation

et al. 2017

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“…Highly strained methylenecyclopropanes undergo transition metal complex promoted ring opening to afford various products, depending on the kind of metal complex used and the reaction conditions. Rhodium(I) complexes promote ring-opening addition of methylenecyclopropane with alkenes, hydrosilylation to give acyclic organosilanes, and intramolecular phenylation of the cyclopropane via ring opening, as well as isomerization to give 1,3-dienes or their Rh complexes. , Much less attention has been paid to the mechanism involved in the reactions and, in particular, the roles of the Rh complexes that promote C−C bond activation and subsequent bond formation reactions to produce the functionalized products. In this paper we report the reactions of substituted methylenecyclopropanes with RhH(CO)(PPh 3 ) 3 and IrH(CO)(PPh 3 ) 3 , leading to their ring-opening isomerization into the corresponding 1,3-dienes, and the isolation of the intermediate organo−rhodium and −iridium complexes.…”

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Hydrido−Rhodium(I) and −Iridium(I) Complex Promoted Ring-Opening Isomerization of Unsymmetrically Substituted Methylenecyclopropanes into 1,3-Dienes. Structures of Intermediates and Reaction Pathways

2001

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Phenyl-1-methylenecyclopropane and 2,2diphenyl-1-methylenecyclopropane react with MH(CO)-(PPh 3 ) 3 (M ) Rh, Ir) to produce 1,3-dienes or the intermediate Rh and Ir complexes having a 3-butenyl ligand, depending on the conditions. The structures and chemical properties of the obtained complexes suggest plausible pathways for the ring-opening isomerization of the methylenecyclopropanes to the corresponding dienes.

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