The reactivity of complexed carbocycles

Salzer, Albrecht; Egolf, T.; Linowsky, Lothar; Petter, W.

doi:10.1016/s0022-328x(00)88376-x

Cited by 27 publications

(10 citation statements)

References 12 publications

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“…spectrum of cis-[(CO),Fe @-CO) (C8H8)Fe (CO),], however, exhibits a single peak for the CxH8-unit, even at -100" [9]. Additional examples of this phenomenon were given in our own previous work [ 11 [4], in which all cisoid dimetallic complexes with bridging cyclooctatetraene showed fluxional behaviour down to -120", the lowest temperature we could reach for solubility reasons, whereas the trunsoid compounds proved non-fluxional even at room temperature.…”

Section: Results Andmentioning

confidence: 97%

“…In addition, since cyclopropabenzenes are usually very unstable compounds, their preparation also represents a considerable synthetic challenge. Recent achievements in the field consist in the synthesis of both isomeric cyclobutacyclopropabenzenes [4] [5]. Extension to the arene homologues led to the discovery of several cyclopropanaphthalenes [6] including the shock-sensitive 1fi.…”

Section: Discussionmentioning

confidence: 99%

“…Our recent work on heterodimetallic compounds with bridging cyclooctatetraene has revealed a quite general synthetic route to such complexes [ I ] [4]. It was shown that cycloolefin complexes, i.e.…”

mentioning

confidence: 99%

“…A closed-shell configuration for both metal centres is formally achieved either via a donor (metal, metal)-bond or an unsymmetrical bonding mode of the bridging cyclooctatetraene. Structural arguments were obtained by spectroscopic as well as X-ray data [2] [4]. Curiously, the Io3Rh-NMR.…”

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confidence: 99%

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Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure

Salzer

Egolf

Philipsborn

1982

Helvetica Chimica Acta

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SummaryThe synthesis of dimetallic olefin complexes of the type L'M'C7H7M2L2 (M' = Fe, Co, Rh; M2= Rh, Ir, Pd; L' = CO, C5H5; L2= diene, allyl, P (OR),) is described. The fluxional structures were investigated by I3C-, 57Fe-and Io3Rh-NMR.-spectroscopy, and a cisoid dimetallic coordination, including a (metal, metal)-bond, can be deduced for the C,H,-ring. 57Fe-and Io3Rh-chemical shifts give indications for the charge distribution in the 34e-complexes. The homodimetallic complex (Cp) Rh (tropone) Rh (Cp) (13, Cp = cyclopentadienyl) and the corresponding 2-methoxytropone complex 14 were synthesized in addition to the above mentioned complexes. A fluxional bis (1-3-~-allyl)-coordination of the two Rh-atoms was derived from the temperature-dependent 13C-NMR.-spectra. A spin simulation of the (Cp)-multiplets of 12 and 13 yields information about (Rh,Rh)-spin-coupling which amounts to z 5 Hz at 30".

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Section: Results Andmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure

Salzer

Egolf

Philipsborn

1982

Helvetica Chimica Acta

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“…9,10 It is remarkable that planar COT rings can also be found in metal complexes. [11][12][13][14][15][16][17][18][19] This article has been dedicated to Prof. Tadeusz Marek Krygowski in recognition of his significant contribution to the field of computational organic chemistry.…”

Section: Introductionmentioning

confidence: 99%

Cyclooctatetraene dianion—an artifact?

Dominikowska

Palusiak

2011

J Comput Chem

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Cyclooctatetraene in its dianionic form (COT(2-)) is considered to be partially or fully aromatic due to the fact that, unlike its neutral counterpart, it adopts planar structure with CC bonds equalized. However, some authors report that this dianion is neither planar nor aromatic. Thus, we performed a detailed analysis of the COT(2-) case. The influence of several technical parameters on the result of calculations on COT(2-) was investigated. It appears from our analysis that the use of some specific level of approximation may lead to very misleading results in which the COT ring occurs in its neutral structure, in fact being neither planar nor aromatic. Additionally, our results may suggest that COT(2-) dianion is rather an artificial structure (being the result of specific basis set description) and should not occur in experimental conditions.

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Kooperative Wirkung in π1‐Ligand‐verbrückten Zweikernkomplexen, XIII. Unerwartet schwache d‐d‐Wechselwirkungen in synfacialen heterodinuklearen μ1‐Cyclooctatetraenkomplexen vom Typ {(CpCr)[(CO)₃M′]}μ1‐Cot (M′Fe, Cr, W)

et al. 1993

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Cooperative Effects in π1‐Ligand‐Bridged Dinuclear Complexes, XIII[1]. – Unexpected Weak d‐d Interactions in Synfacial Heterodinuclear μ1‐Cyclooctatetraene Complexes of the Type {(CpCr)[(CO)3M′]}μ1‐Cot (M′Fe, Cr, W) The heterodinuclear complexes {(CpCr)[(CO)3M′]}μ1‐Cot (CotC8H8; M′Fe, Cr, W) (5 – 7) and {(Cp*Cr)[(CO)3Cr]}μ1‐Cot (Cp*C5Me5) (9) are synthesized by the reaction of the corresponding mononuclear Cot complexes CpCr(η61‐Cot) (4) and Cp*Cr(η61‐Cot) (8), respectively, with M′(CO)3(EtCN)3 (M′Cr, W) and with Fe2(CO)9. The CrFe compound 5 is obtained in very low yield only. However, much better yields of 5 are achieved in the reaction of CrCl2 and CrCp2 with (CO)3Fe(η41‐Cot) (10) in the presence of an excess of Zn. X‐ray structure determinations of 5 and 6 reveal synfacial configurations of the CpCr and M′(CO)3 units with a μ1‐η5:3‐ and μ1‐η4:51‐Cot bonding mode for 5 and 6, respectively. The metal – metal distances are 2.9369(13) Å for 5 and 2.81(2) Å for 6 indicating metal – metal single bonds. 5 contains 33 valence electrons (ve) and is paramagnetic with one unpaired electron. A well‐resolved fluid‐solution ESR spectrum of 5 shows a 53Cr and 1H hyperfine structure (hfs). The 1H hfs can be calculated with three different 1H hyperfine coupling constants (1H hfcc) indicative of protons in α1‐position with respect to the paramagnetic metal center: one 1H hfcc of the five Cp protons (1.68 G), one of three (3.32 G) and one of two protons of the Cot ligand (5.04 G). This agrees with the Cot bonding mode of the CpCr unit in the crystalline phase. The ratio of 3:2 protons for the Cot ligand prove the rigidity of the Cot ligand on the ESR time scale. The excellent agreement of the ESR data of the liquid and frozen solution ESR spectra of 5 with the ESR data of the mononuclear complex CpCr(η61‐Cot) leads to the conclusion that the unpaired electron in 5 must predominantly be chromium‐centered. 6, 7, and 9 have 31 ve and are paramagnetic with three unpaired electrons as shown by means of ESR spectroscopy and magnetic measurements. The calculations of the quartet ESR spectra of 6, 7, and 9 reveal zero‐field splitting parameters D ranging from 3.6 to 4.8 cm–1 which are similar to that of the mononuclear quartet compound vanadocene. The small range in the parameters D prove the minor influence of the second metal on going from Cr to W. Hence, the three unpaired electrons are assumed to be mainly localized on the Cr center of the CpCr unit. Cyclic voltammetry studies result in the redoxcascade − 2 ⇄ − 1 ⇄ 0 ⇄ + 1 for 5 and 7 at +20°C and for 6 at –35°C. However, at +20°C 6 and 9 only show one electrochemically reversible reduction wave 0/–1, whereas the oxidation 0/+1 and the second reduction –1/–2 are irreversible. The redox potentials indicate a considerable influence of the metal combinations. On the strength of the ESR spectroscopic results and according to the results of crystal structure determinations, an isolobal relationship is drawn between the (CO)3M′(η8 – ×1‐Cot) fragment and a cyclic organic π1‐ligand wi...

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The reactivity of complexed carbocycles

Cited by 27 publications

References 12 publications

Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure

Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure

Cyclooctatetraene dianion—an artifact?

Kooperative Wirkung in π1‐Ligand‐verbrückten Zweikernkomplexen, XIII. Unerwartet schwache d‐d‐Wechselwirkungen in synfacialen heterodinuklearen μ1‐Cyclooctatetraenkomplexen vom Typ {(CpCr)[(CO)₃M′]}μ1‐Cot (M′Fe, Cr, W)

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The reactivity of complexed carbocycles

Cited by 27 publications

References 12 publications

Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure

Dimetallic Complexes with Bridging Seven‐membered Cycloolefins. Synthesis, Multinuclear NMR.‐Spectroscopic Properties and Structure

Cyclooctatetraene dianion—an artifact?

Kooperative Wirkung in π1‐Ligand‐verbrückten Zweikernkomplexen, XIII. Unerwartet schwache d‐d‐Wechselwirkungen in synfacialen heterodinuklearen μ1‐Cyclooctatetraenkomplexen vom Typ {(CpCr)[(CO)3M′]}μ1‐Cot (M′Fe, Cr, W)

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Kooperative Wirkung in π1‐Ligand‐verbrückten Zweikernkomplexen, XIII. Unerwartet schwache d‐d‐Wechselwirkungen in synfacialen heterodinuklearen μ1‐Cyclooctatetraenkomplexen vom Typ {(CpCr)[(CO)₃M′]}μ1‐Cot (M′Fe, Cr, W)