(eta3-Triphenylcyclopropenyl) tricarbonylcobalt

Chiang, T.; Kerber, Robert C.; Kimball, S. David; Lauher, Joseph W.

doi:10.1021/ic50196a058

Cited by 45 publications

(26 citation statements)

References 1 publication

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“…Table 2 ing for the ring is consistent with substantial cyclobutendiylium character for this moiety (14)(15)(16)(17). If one turns one's attention to the pendent guaiazulene groups in bisguaiazulenylsquaraine (Table l), then several carbons show sizeable downfield (10 ppm) shifts from the parent guaiazulene.…”

Section: Fig 2 the 250 Mhz 'H Nmr Spectrum Of Bis(4-dibutylamino-2-mentioning

confidence: 59%

Conformational isomerism in squaraines: saturation transfer NMR studies on hydroxy squaraines

Kazmaier¹,

Hamer²,

Burt³

1990

Can. J. Chem.

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Can. J. Chem. 68, 530 (1990). The proton and I3C NMR of azulene and dialkylaminohydroxyphenyl squaraines have been investigated. The four-membered ring carbon resonances occur in the 180-190 ppm range and are attributed to the cyclobutenediylium character of this structure. Some charge delocalization from the central ring to the pendent aromatic substituents was also observed, indicative of a substituent effect of the squaraine moiety on aminoaromatic systems equivalent to that of a formyl or acetyl group. Hydroxy squaraines 10 and 11 show the presence of two isomeric squaraine species in the proton NMR in deuterochloroform. Saturation transfer experiments confirm that these species are readily interconverted, and cisltrans isomerism (9a 9b) is consistent with these observations. The free energy difference between the two isomers at 318 K is calculated to be 3.0 and 3.2 kJ/mol for hydroxysquaraines 10 and 11 respectively.Key words: squaraines, saturation transfer, NMR. On a examink les spectres RMN du proton et du I3c de l'azulkne et des dialkylaminohydroxyphCnyl squara'ines. Les resonances des carbones du cycle 5 quatre chainons sont observkes dans la plage allant de 180 a 190 ppm et elles sont attribukes au caractere cyclobutenediylium de cette structure. On a aussi observe une certaine dClocalisation de la charge du noyau central vers les substituants attaches au noyau aromatique; ces observations suggerent qu'il existe un effet de substituant de la portion squaraine sur les systkmes aminoaromatiques equivalent a celui d'un groupement formyle ou acyle. Dans les spectres RMN du proton des hydroxy squarai'nes 10 et 11 en solution dans le deutkrochloroforme, on observe la prksence de deux especes isomkres. Des expkriences de transfert de saturation confirment que ces especes se transforment facilement l'une dans I'autre; une isomkrie cislrrans (90 S 9b) est en accord avec ces observations. On a calcule que, a 318 K, les diffkrences d'knergie libre entre les deux isomeres sont de 3,O et de 3,2kJ/mol respectivement pour les hydroxysquarai'nes 10 et 11.

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Section: Fig 2 the 250 Mhz 'H Nmr Spectrum Of Bis(4-dibutylamino-2-mentioning

confidence: 59%

Conformational isomerism in squaraines: saturation transfer NMR studies on hydroxy squaraines

Kazmaier¹,

Hamer²,

Burt³

1990

Can. J. Chem.

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“…Prediction of the existence of compound 6 in the staggered conformation is consistent with the results of X ray studies of tricarbonyl(η 3 triphenylcyclo propenyl)cobalt. 15 According to calculations, the cyclopropenyl fragment in complex 6a is characterized by equalized carbon-car bon bonds 1.416 Å long, which is in the range between the ordinary and double bond lengths. The Co-C interatom ic distances (1.994 Å) somewhat exceed the sum of the covalent radii of carbon and cobalt (1.93 Å); 16 the metal atom and the center of the basal ring are separated by 1.819 Å.…”

Section: Resultsmentioning

confidence: 99%

π-Complexes of transition metal tricarbonyls with cyclopolyenes and their boron analogs

2009

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ul. Chekhova, 344006 Rostov on Don, Russian FederationThe structures and stability of complexes of transition metal tricarbonyls (M = Co, Fe, Mn, Cr) with hydrocarbon and borane basal rings, (C n H n )M(CO) 3 and (B n H 2n )M(CO) 3 , respec tively, as well as internal rotation of the metal tricarbonyl fragments in these systems were studied by the DFT B3LYP/6 311+G(df,p) method. Replacement of hydrocarbon basal frag ments by isoelectronic borane rings leads to strengthening of the interaction between the apical and basal fragments, but does not change the trend in the heights of barriers to internal rotation. In all cases, the metal tricarbonyl fragment stabilizes the nonclassical planar form of the borane rings, whereas the complexes of metal tricarbonyls based on the classical nonplanar borane conformations are less thermodynamically stable.Key words: transition metal tricarbonyls, metalloboranes, stereochemical nonrigidity, quan tum chemical calculations.π Complexes of transition metal tricarbonyls with cy clopolyenes (C n H n )M(CO) 3 have been well studied. 1,2 To date, various 18 electron complexes (C n H n )M(CO) 3 (n = 4-8) with apical groups containing transition metals from Ti to Ni have been synthesized and structurally char acterized. Such compounds possess high thermal stability and are stereochemical nonrigid due to almost free rota tion of the metal tricarbonyl group about the symmetry axis. A salient feature of these systems is the possibility for induced aromaticity to occur. 3 For instance, the interac tion of the Fe(CO) 3 group with the antiaromatic cyclo butadiene fragment in complex 1 stabilizes the square con figuration of the basal ring with equalized carbon-carbon bond lengths. Compound 1 exhibits characteristic aro matic properties; this made it possible to introduce the term "metalloaromaticity". 4,5The first metallaborane synthesized was ferraborane 2 (Scheme 1) in which the cyclobutadiene ring is replaced by borane. 6 This compound is isostructural and isoelec tronic to the hydrocarbon analog 1. Similarly to the cy clobutadiene fragment, which is stable in the rectangular form with alternating bonds (system with equalized bonds is unstable), the planar four membered borane ring B 4 H 8 is also unstable and has a boat structure in the free state.Thus, the Fe(CO) 3 group stabilizes not only the sym metrical form of cyclobutadiene, but also the nido form of isoelectronic borane B 4 H 8 , which does not exist in the free state. 6-8 This leads to a new stable metallaborane 2.At present, investigations of such systems that relate the chemistry of boranes to organometallic chemistry and co ordination chemistry is a topical avenue of experimental and theoretical research, which offers prospects for the discovery of novel compounds with unusual structures and properties. 6-8One can expect that stabilization of other borane rings B n H 2n (n = 3, 5, 6) by the corresponding metal tricarbonyl fragments will lead to a new family of metallaborane sys tems 3-5 isoelectronic and isostructural to the t...

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“…The reactions of cyclopropenylium cations with low valent metal centers can lead to (η 3 -cyclopropenyl)- (Chiang et al, 1979; Hughes et al, 1986, 1993; Lichtenberger et al, 1993; Ghilardi et al, 1995), (η 2 -cyclopropenyl)- (Mealli et al, 1982), and (η 1 -cyclopropenyl) (Gompper and Bartmann, 1985) metal complexes. The hapticity of the product depends on the ring's substituents, the metal, and the other ligands on the metal (Figure 7).…”

Section: π-Complexesmentioning

confidence: 99%

“…Evidence of the η 3 bonding model for (C 3 R 3 )Co(CO) 3 was confirmed experimentally by Lichtenberger et al by photoelectron spectroscopy (Lichtenberger et al, 1993). This bonding model is applicable to complexes with the general formulas (C 3 R 3 )ML 3 (where M = Co, Rh, Ir) (Chiang et al, 1979) and (C 3 R 3 )ML 2 X (where M = Ni, Pt, Pd; X = anionic ligand; L = neutral ligand) (Mealli et al, 1981, 1983; Miki et al, 1988; Kuchenbeiser et al, 2008). Since d 9 ML 3 and d 5 ML 5 complexes are isolobal, this η 3 bonding is also appropriate for complexes with the general formula (C 3 R 3 )ML 3 X 2 (where M = Ru) (Ditchfield et al, 1993; Morton and Selegue, 1999) and (C 3 R 3 )ML 4 X (where M = Mo or W) (Hayter, 1968; Drew et al, 1981; Hughes et al, 1985).…”

Section: π-Complexesmentioning

confidence: 99%

Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

2019

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Transition metal-stabilized carbocations are characterized by synthetically valuable interactions, yet, to date there are no comprehensive reports of the many bonding modes that can exist between a metal and carbocation. This review summarizes developments in these complexes to provide a clear picture of their properties and reactivities. In order to strategically exploit them, we propose this summary of the different bonding modes for transition metal-carbocation complexes. These models will help chemists understand the orbital interactions involved in these compounds so that they can approach their synthetic goals most effectively. Multiple transition metals and carbocations will be discussed.

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(eta3-Triphenylcyclopropenyl) tricarbonylcobalt

Cited by 45 publications

References 1 publication

Conformational isomerism in squaraines: saturation transfer NMR studies on hydroxy squaraines

Conformational isomerism in squaraines: saturation transfer NMR studies on hydroxy squaraines

π-Complexes of transition metal tricarbonyls with cyclopolyenes and their boron analogs

Molecular Orbital Insights of Transition Metal-Stabilized Carbocations

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