o-Carboranylcarbene. A largely localized divalent carbon intermediate

Hutton, R. S.; Roth, Heinz D.; Chari, Sarangan

doi:10.1021/j150607a004

Cited by 13 publications

(6 citation statements)

References 2 publications

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“…61 In favorable cases, the ESR spectra of these carbenes exhibit two sets of triplet signals with sufficiently different ZFS parameters to detect and characterize the isomers. 77,78 The magnitude of the ZFS parameters D is largely determined by the spin-spin dipolar interaction of the two electrons at the divalent carbon atom. In spite of the predominance of this one-center interaction, the spin density at atoms several bonds removed from the divalent carbon atom can also have a significant effect on the ZFS parameters.…”

Section: Geometrical Isomerismmentioning

confidence: 99%

“…The assignment of the ZFS parameters to a specific conformer is made possible by a point spin model. 77,78…”

Section: Geometrical Isomerismmentioning

confidence: 99%

“…Triplet carbenes whose divalent carbon atom is substituted with an sp 2 hybridized carbon atom may exist in two rotameric forms, which are stable at very low temperatures . In favorable cases, the ESR spectra of these carbenes exhibit two sets of triplet signals with sufficiently different ZFS parameters to detect and characterize the isomers. , …”

Section: Electron Spin Resonance Spectroscopymentioning

confidence: 99%

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Persistent Triplet Carbenes

Hirai,

Itoh,

Tomioka

2009

Chem. Rev.

144

123

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Section: Geometrical Isomerismmentioning

confidence: 99%

“…The assignment of the ZFS parameters to a specific conformer is made possible by a point spin model. 77,78…”

Section: Geometrical Isomerismmentioning

confidence: 99%

Section: Electron Spin Resonance Spectroscopymentioning

confidence: 99%

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Persistent Triplet Carbenes

Hirai,

Itoh,

Tomioka

2009

Chem. Rev.

144

123

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“…Carboranylcarbene (l-CH-1,2-C2BioHh) is also known to have a triplet ground state,11 but as Jones and co-workers have shown in a number of studies,12-1419 the singlet state is much more reactive. Recently, Jones and co-workers16-18 have synthesized a carboranylcarbene with the carbene center attached to a boron vertex (3-CH-1,2-C2B 11) rather than to carbon (1-position). For these carbenes, the triplet states show enhanced reactivity as judged by an increase of products due to hydrogen abstraction.…”

Section: Introductionmentioning

confidence: 99%

Singlet-Triplet Splittings in Carboranylcarbenes and Carboranylnitrenes. A Theoretical Study

McKee¹

1994

J. Phys. Chem.

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Ab initio calculations have been carried out on the o-carborane cage (1,2-C2B10H1~) with a carbene (-CH) or nitrene (-N) substituent at the 1-, 3-, or 9-position. When the carbene or nitrene is attached to the 1-position (carbon vertex), the singlet carbene is stabilized relative to the triplet. In contrast, when attached to the 3-or 9-position (boron vertex), the triplet is stabilized. Except for l-CH-l,2-C2Bl,& (where the singlettriplet splitting is small), all carboranylcarbenes and carboranylnitrenes considered have triplet ground states. The lowest-energy singlet state of the carboranylnitrene is the open-shell singlet when nitrogen is attached to the 3-or 9-position and closed-shell singlet when attached to the 1-position. All carboranylcarbenes are predicted to be bent (singlets, 108-1 14"; triplets, 129-140"). However, the triplet inversion stationary structure is nearly linear (179-180") and, for substitution at the 3-or 9-position, only 1.0 kcal/mol higher than the triplet minimum.

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“…Under conditions where the ratio of the AB coupling constant to the chemical shift difference between sites A and B, Av(AB), is large, a second-order three-line AB pattern can appear.13 There (10) Spectral data for 2: bp 158-159 °C (ca. 95% yield); 'H NMR (CDClj) 6 2.36 (t, 2 H, 7HD = 2.1 Hz), 7.18 (m, 2 H), 7.28 (dd, 1 H, J = 6.83 Hz, J = 1.9 Hz), 7.40 (dd, 1 H, J = 6.82 Hz, 7= 1.5 Hz); 13C NMR (CDClj) 19.7 (t), 126.6 (d), 127.1 (d), 129.0 (d), 130.8 (d), 134.3 (s), 135.9 (s). (11) Spectral data for 2-Cr: mp 99-101 °C (lit.…”

mentioning

confidence: 99%