Fluxional nature of benzo- and naphthocyclooctatetraeneiron carbonyl complexes

Stucki, Heinz

doi:10.1021/ja00779a059

Cited by 18 publications

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“…Ee(l) 0.50181 (7) 0.15578 (6) 0.18764 (8) 0.00375 (4) 0.00346 (5) 0.00438 (6) 0.00055 (9) 0.0005 (1) 0.0007 (1) Fe(2) 0.56717 (7) 0.18658 (7) 0.96769 (8) 0.00377 (4) 0.00373 (5) 0.00477 (6) 0.00014 (10) 0.0006 (1) 0.0010 ( -0.0011 (8) -0.0009 (9) 0.0036 (9) C(12) 0.5884 (6) 0.2364 (6) 0.2415 (7) 0.0065 (5) 0.0057 (5) 0.0066 (6) 0.0002 (9) 0.0018 (10) 0.0009 (10) C( 21) 0.4652 (5) 0.2691 (6) -0.0372 (7) 0.0049 (4) 0.0074 (5) 0.0056 (5) 0.0020 (8) 0.0023 (8) 0.0042 (18) C( 22) 0.6572 (5) 0.2810 (5) 0.9982 (6) 0.0048 (4) 0.0043 (4) 0.0069 (6) -0.0021 (7) 0.0033 (8) -0.0013 ( 9) C( 23) 0.5885 (6) 0.1952 (6) 0.8227 (7) 0.0063 (5) 0.0055 (5) 0.0055 (5) -0.0007 (9) 0.0001 (9) 0.0008 (10) C(l) -0.0042 (12) -0.0006 (13) P atoms were included in the calculated structure factors using /' and /" values given by Cromer and Liberman. 16 A series of two successive difference Fourier maps allowed location of all non-hydrogen atoms except the methyl carbon atoms in triethylphosphine.…”

Section: Methodsmentioning

confidence: 99%

Carbon-13 nuclear magnetic resonance study of the fluxional character of the .eta.6-(bicyclo[6.2.0]dodeca-2,4,6-triene)hexacarbonyldiiron(Fe-Fe) and a triethylphosphine derivative thereof, and the crystal structure of the latter

Cotton¹,

Hunter²

1975

J. Am. Chem. Soc.

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The I3C N M R spectrum of the title compound (2) has been recorded at various temperatures from -120 to 102'. The four resonances for the eight-membered ring which are observed at room temperature broaden at -30' and are totally collapsed at about -85'; solubility problems precluded further study of these signals. The carbonyl carbon resonances were observed using enriched samples. The six-line spectrum expected from the crystal structure is observed at -120'. Four lines collapse and disappear into the base line between -120 and -88'. From -88 to -50' these four and one other signal reform into two signals of relative intensities 2:3. From ca. -50 to +102O the signal of intensity 2 and the previously unbroadened signal of intensity 1 collapse and re-form as a signal of intensity 3, while the signal of intensity 3 which was present at -50' sharpens. These changes can be understood in terms of a twitching process of the Fe2(C0)6 group relative to CioHl2 ligand followed by local averaging in one Fe(CO)3 group, followed by averaging within the other Fe(CO)3 group. No gliding motion or internuclear exchange of CO groups is allowed. The interpretation here is the same as that given previously for (CsHlo)Fe2(C0)6 (1). but the interpretation is more straightforward because there is less overlap of the three ppcesses. Moreover, by comparison of the slow exchange limit spectra of 1 and 2 a partial assignment can be made which is sufficient to allow an unequivocal determination that local scrambling occurs first about the allyl-bound iron atom. This point remained uncertain on the basis of data for 1 alone. The molecule (CioH12)Fe2(C0)5PEt3 was prepared and the position of the PEt3 ascertained by X-ray crystallography. From its I3C spectrum still further information is obtained which confirms all of the previous conclusions.Although the structural and dynamical properties of molecules of the general type 1-5 have been studied for a number of years, a complete and definitive understanding of their fluxional behavior has not yet been achieved.' The crystal structures of four of them, namely 1,2 2,3 3,4 and 55 about 12'. It has not yet been proved whether this C O scrambling occurs locally within each Fe(C0)3 group or involves passage of C O groups from one metal atom to the other, although there is indirect evidence favoring the former. It may also be noted that a 180' rotation of the entire t X = -CH,

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Section: Methodsmentioning

confidence: 99%

Carbon-13 nuclear magnetic resonance study of the fluxional character of the .eta.6-(bicyclo[6.2.0]dodeca-2,4,6-triene)hexacarbonyldiiron(Fe-Fe) and a triethylphosphine derivative thereof, and the crystal structure of the latter

Cotton¹,

Hunter²

1975

J. Am. Chem. Soc.

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Organometallic Complexes of Dienes and Polyenes

Donaldson

2009

Patai's Chemistry of Functional Groups

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Organometall-Verbindungen mit intramolekularer π-Olefin-Metall-Koordination

Omae

2006

Angewandte Chemie

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In diesem Aufsatz werden Komplexe vom Typ X,M-R zusammenfassend beschrieben, in denen ein a-gebundener organischer Ligand R zusltzlich durch eine Olefin-n-Bindung rnit dem Metall M verkniipft ist. Mit anderen Worten: Die Komplexe enthalten Metallacyclen mit dreieinhalb, viereinhalb, fiinfeinhalb usw. Gliedern. Fiinfeinhalbgliedrige Ringsysteme kennt man hauptsachlich rnit 4-Pentenyl-, 1,4-Pentadienyl-, Allylnorbornyl-, Allylnorbornenyl-, Cyclooctenyl-und endo-Dicyclopentadienyl-Liganden. Metallacyclen dieser GroBe sind spannungsfrei und stabil. Donorliganden wie Amine oder Phosphane konnen die koordinierte Doppelbindung des n-Liganden vom Metall verdrangen. Diese C=C-Doppelbindung wird durch die Koordination von ca. 133 pm auf 136 bis 146 pm verlangert.

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Fluxional nature of benzo- and naphthocyclooctatetraeneiron carbonyl complexes

Abstract: Contrary to statements in the literature,1 shift isomerism of 3,4,5,6-Zeira/za/riobenzocyclooctatetraeneiron tricarbonyl (1) and its 2,3-naphtho analog 2 is sufficiently rapid to label them fluxional molecules.

Cited by 18 publications

References 1 publication

Carbon-13 nuclear magnetic resonance study of the fluxional character of the .eta.6-(bicyclo[6.2.0]dodeca-2,4,6-triene)hexacarbonyldiiron(Fe-Fe) and a triethylphosphine derivative thereof, and the crystal structure of the latter

Carbon-13 nuclear magnetic resonance study of the fluxional character of the .eta.6-(bicyclo[6.2.0]dodeca-2,4,6-triene)hexacarbonyldiiron(Fe-Fe) and a triethylphosphine derivative thereof, and the crystal structure of the latter

Organometallic Complexes of Dienes and Polyenes

Organometall-Verbindungen mit intramolekularer π-Olefin-Metall-Koordination

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