A non-empirical and HAM/3 study of the geometry, conformational behaviour and electronic structure of isomeric vinylpyridines

Barone, Vincenzo; Bianchi, Nadia; Lelj, Francesco; Abbate, Giancarlo; Russo, Nino

doi:10.1016/0166-1280(84)80097-4

Cited by 19 publications

(3 citation statements)

References 31 publications

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“…As according to calculations [19] and NMR studies [20] the preferred conformation of free 2-vinylpiridine is A rather than B, steric repulsion between the vinyl group and the AuCl 3 moiety of the complex is likely responsible of the change in the conformation upon coordination.…”

Section: Adductsmentioning

confidence: 98%

Gold(III) adducts of 2-vinyl- and 2-ethylpyridine and cyclometallated derivatives of 2-vinylpyridine: Crystal structure of the cyclometallated derivative [Au(k2-C,N–CH2CH(Cl)–C5H4N)(PPh3)Cl][PF6]

Cinellu

Cocco

Minghetti

et al. 2009

Journal of Organometallic Chemistry

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Section: Adductsmentioning

confidence: 98%

Gold(III) adducts of 2-vinyl- and 2-ethylpyridine and cyclometallated derivatives of 2-vinylpyridine: Crystal structure of the cyclometallated derivative [Au(k2-C,N–CH2CH(Cl)–C5H4N)(PPh3)Cl][PF6]

Cinellu

Cocco

Minghetti

et al. 2009

Journal of Organometallic Chemistry

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“…Also, Δδ for the 3-H resonance in 2-vinylpyridine is downfield (+0.12 ppm) but upfield for other 2-substituted pyridines (−0.04 to −0.08 ppm). Previous calculations and NMR studies showed that the preferred conformation of free 2-vinylpyridine is ii rather than i (cf. Figure b).…”

Section: Resultsmentioning

confidence: 99%

Metal Coordination by Sterically Hindered Heterocyclic Ligands, Including 2-Vinylpyridine, Assessed by Investigation of Cobaloximes

et al. 2006

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Structural and 1H NMR data have been obtained for cobaloximes with the bulkiest substituted pyridines reported so far. We have isolated in noncoordinating solvents the complexes CH3Co(DH)2L (methylcobaloxime, where DH = the monoanion of dimethylglyoxime) with L = sterically hindered N-donor ligands: quinoline, 4-CH3quinoline, 2,4-(CH3)2pyridine, and 2-R-pyridine (R = CH3, OCH3, CH2CH3, CH=CH2). We have found that the Co-N(ax) bond is very long in the structurally characterized complexes. In particular, CH3Co(DH)2(4-CH3quinoline) has a longer Co-N(ax) bond (2.193(3) A) than any reported for methylcobaloximes. The main cause of the long bonds is unambiguously identified as the steric bulk of L by the fairly linear relationship found for Co-N(ax) distance vs CCA (calculated cone angle, CCA, a computed measure of bulk) over an extensive series of methylcobaloximes. The linear relationship improves if L basicity (quantified by pKa) is taken into account. In anhydrous CDCl3 at 25 degrees C, all complexes except the 2-aminopyridine adduct exhibit 1H NMR spectra consistent with partial dissociation of L to form the methylcobaloxime dimer. 1H NMR experiments at -20 degrees C allowed us to assess qualitatively the relative binding ability of L as follows: 2,4-(CH3)2pyridine> 4-CH3quinoline approximately = quinoline approximately = 2-CH3pyridine > 2-CH3Opyridine > 2-CH3CH2pyridine > 2-CH2=CHpyridine. The broadness of the 1H NMR signals at 25 degrees C suggests a similar order for the ligand exchange rate. The lack of dissociation by 2-aminopyridine is attributed to an intramolecular hydrogen bond between the NH2 group and an oxime O atom. The weaker than expected binding of 2-vinylpyridine relative to the Co-N(ax) bond length is attributed to rotation of the 2-vinyl group required for this bulky ligand to bind to the metal center, a conclusion supported by pronounced changes in 2-vinylpyridine signals upon coordination.

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“…A deeper analysis of the results of Table I1 can be performed by remembering that the torsional potential of azabiphenyls is governed by two factors, namely the r interaction between the two rings, which tends to keep the molecules planar (the so-called conjugation energy E , ) and the interactions between nonbonded atoms belonging to different rings (the so-called steric E, and electrostatic E,, energies), which may generally be alleviated by deviation from planarity [42,43]. 'V, = -25.0; V, = -7.2; V , = -2.0; the absolute minimum occurs at 6 = 180"; the value of the secondary (nearly cis) minimum is reported in the table.…”

Section: (2)mentioning

confidence: 99%

Conformational behavior of azabiphenyls

Barone

Lelj

Russo

1986

Int J of Quantum Chemistry

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The conformational behavior of biphenyl-like compounds constituted by benzene and/or azabenzenes has been investigated at the sm-3G Hartree-Fock level. Although the sTO-3G basis set probably overestimates conjugative attraction, it seems able to provide reliable general trends. In this connection the analysis of over 30 molecules shows that compounds with the same ortho substituents (including nitrogen lone pairs) have very similar conformational behavior, irrespective of their composition. Furthermore, the comparison of different isomers shows that repulsive interactions decrease in the order hydrogen-hydrogen > lone pair-lone pair 9 hydrogen lone pair. Conjugative, electrostatic, and sberic interactions have also been expressed by well known semiempirical functions, thus allowing a better analysis of the overall torsional potential.

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A non-empirical and HAM/3 study of the geometry, conformational behaviour and electronic structure of isomeric vinylpyridines

Cited by 19 publications

References 31 publications

Gold(III) adducts of 2-vinyl- and 2-ethylpyridine and cyclometallated derivatives of 2-vinylpyridine: Crystal structure of the cyclometallated derivative [Au(k2-C,N–CH2CH(Cl)–C5H4N)(PPh3)Cl][PF6]

Gold(III) adducts of 2-vinyl- and 2-ethylpyridine and cyclometallated derivatives of 2-vinylpyridine: Crystal structure of the cyclometallated derivative [Au(k2-C,N–CH2CH(Cl)–C5H4N)(PPh3)Cl][PF6]

Metal Coordination by Sterically Hindered Heterocyclic Ligands, Including 2-Vinylpyridine, Assessed by Investigation of Cobaloximes

Conformational behavior of azabiphenyls

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