Influence of Phenyl Substituents on Diamagnetic Cobalt(III) Dithiocarbamate Complexes

1990 ◽  
Vol 43 (8) ◽  
pp. 1335 ◽  
Author(s):  
PC Healy ◽  
JV Hanna ◽  
NV Duffy ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Chemical Shifts ◽  
Saturated Hydrocarbon ◽  
Substituent Effects ◽  
Unsaturated Hydrocarbon ◽  
Good Evidence ◽  
Ligand Field ◽  
Electronic Effects ◽  
Space Group ◽  
Methyl Phenyl ◽  
Field Strengths

Single-crystal X-ray structural determinations have been recorded at c.295 K for the tris ( dithiocarbamato )cobalt(III) compounds [Co(S2CNMePh)3] and [Co(S2CNPh2)3]. [Co(S2CNMePh)3] crystallizes in space group P21/a with a 25.207(6), b 12.778(2), c 9.497(2)Ǻ, β 116.40(2)°. [Co(S2CNPh2)3] crystallizes in space group Pī with a 14.979(6), b 13.169(4), c 10.683(3)Ǻ, α 71.53(3),β 88.15(3),γ 82.35(3)°. The structures were refined to residuals of 0.039 and 0.062 for 2184 and 4068 'observed' reflections respectively. The cobalt-59 n.m.r. chemical shift of the sparingly soluble diphenyl compound is found to be 6450 ppm downfield from K3Co(CN)6, compared with 6660 ppm for the methyl phenyl compound and 6830 ppm for the non-phenyl-substituted dimethyl compound, a result reflecting increase in the ligand -field strengths of the ligands in this series of compounds in the order Me2 < Me Ph < Ph2. Average geometric parameters (Ǻ) are: methyl phenyl, Co-S 2.270(6), C-S 1.699(6), C-N 1.341(9), S…S 2.803(2), N-Cphenyl 1.446(5), N-Cmethyl 1.45(1); diphenyl, Co-S 2.267(8), C-S 1.699(4), C-N 1.335(4), S…S 2.805(2), N-Cphenyl 1.449(6). Solid-state carbon-13 chemical shifts for thecarbon atom of the NCS2 fragment are 204, 207 and 210 ppm for [Co(S2CNMe2)3], [Co(S2CNMePh)3] and [Co(S2CNPh2)3] respectively. By comparison, the carbon-13 chemical shifts for cobalt complexes with saturated hydrocarbon substituents which span the range of ligand -field strengths do not show the same systematic trends: [Co(S2CN(CH2)4)3], 201 ppm ; [Co(S2CNEt2)3], 204 ppm ; and [Co(S2CNPri2)3], 204 ppm , [Co(S2CN(CH2Ph)2)3], 207 ppm . For the unsaturated hydrocarbon system, [Co(S2CN(CH)4)3], this value is 211 ppm . These results correspond closely to solution carbon-13 data and constitute good evidence that the ligand substituent effects in the compounds are similar in the two states. The increase in ligand -field strength with phenyl substituent is rationalized in terms of a combination of steric and electronic effects.

scholarly journals Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes

2003 ◽  
Vol 68 (7) ◽  
pp. 525-534 ◽  
Author(s):  
Natasa Valentic ◽  
Gordana Uscumlic
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Charge Densities ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
Vinyl Group ◽  
Proton Chemical Shifts

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.

scholarly journals Substituenteneinflüsse auf die 13C–NMR-chemischen Verschiebungen cis- und trans-konfigurierter Trimethincyanine / Substituent Effects on the 13C NMR Chemical Shifts of Trimethincyanines with cis and trans Configuration

1976 ◽  
Vol 31 (12) ◽  
pp. 1641-1645 ◽  
Author(s):  
Walter Grahn
Keyword(s):  
13C Nmr ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron Systems ◽  
Coupling Constant ◽  
Electronic Effects ◽  
Nmr Chemical Shifts ◽  
Monosubstituted Benzenes ◽  
Cis And Trans ◽  
C Nmr

The 13C NMR chemical shifts of fifteen 6 substituted 2,3-dihydro-1,4-diazepinium salts (cis trimethincyanines) (1) and twelve 2 substituted bis(dimethylamino)trimethinium salts (trans trimethincyanines) (2) have been determined. A comparison of the substituentinduced shifts (13C SCS) of 1 and 2 allows no distinction between steric and electronic effects. In the three 6 п-electron systems 1, 2 and monosubstituted benzenes the 13C SCS are similar for the substituent bearing carbon atoms. A surprisingly large 4JFCCNC coupling constant has been observed.

scholarly journals Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

1973 ◽  
Vol 51 (6) ◽  
pp. 915-926 ◽  
Author(s):  
Gordon K. Hamer ◽  
Ian R. Peat ◽  
W. F. Reynolds
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron System ◽  
Resonance Spectroscopy ◽  
Molecular Orbital Calculations ◽  
Electronic Effects ◽  
Partial Explanation ◽  
Charge Densities ◽  
Related Compounds ◽  
Molecular Framework

Substituent-induced 1H chemical shifts (S.C.S.) for 19 4-substituted α-methyl- and α-t-butylstyrenes have been determined at infinite dilution in C6H12 and 13C S.C.S. have been determined for 0.4 M solutions in CCl4. S.C.S. are correlated with field and resonance substituent parameters and compared with charge densities determined by CNDO/2 MO calculations. The variation of S.C.S. with the dihedral angle, ρ, between phenyl and vinyl groups and the overall pattern of S.C.S. can be largely accounted for by a model of substituent effects based on field, resonance, and π polarization effects, with conjugative interactions varying as cos2ρ. Both 13C chemical shifts and charge densities indicate that the π polarization effect consists of two components: (1) a through-space polarization of the vinyl system by the polar C—X bond and (2) polarization of the entire conjugated styrene π electron system. However, significant deviations are noted for some of the 1H S.C.S. correlations. The CNDO/2 calculations indicate that these deviations are primarily due to electronic effects not predicted by the model outlined above. CNDO/2 calculations for related compounds provide a partial explanation by indicating that the magnitude of the field effect depends upon the nature of the molecular framework.

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. I, 4-Substituted Styrenes

1973 ◽  
Vol 51 (6) ◽  
pp. 897-914 ◽  
Author(s):  
Gordon K. Hamer ◽  
Ian R. Peat ◽  
William F. Reynolds
Keyword(s):  
Field Effect ◽  
Chemical Shifts ◽  
Hydrogen Charge ◽  
Substituent Effects ◽  
Conclusive Evidence ◽  
Resonance Spectroscopy ◽  
Molecular Orbital Calculations ◽  
Electronic Effects ◽  
Charge Densities ◽  
Self Consistent

1H and 13C chemical shifts have been determined for over 20 4-substituted styrenes under conditions corresponding to infinite dilution in a non-polar medium. Correlations of the internal chemical shift difference for the β vinyl protons, Δδ(B − C) with electric field components estimated by a classical electrostatic calculation, with the field parameter F, and with hydrogen charge densities estimated by CNDO/2 MO calculations provide conclusive evidence for the existence of a through-space field effect. CNDO/2 calculations for 4-substituted 1-vinylbicyclo[2.2.2]octanes and ethylene–methylX pairs indicate that this through-space field effect has a geometric dependence similar to that predicted by the Buckingham equation.Correlations of vinyl 1H and 13C chemical shifts and charge densities with field, F, and resonance, R, parameters provide a self-consistent picture of electronic effects in these compounds. 1H chemical shifts for some derivatives are affected by magnetic effects but this does not obscure the overall pattern of electronic effects. This pattern of electronic effects can be completely accounted for by a model which assumes that substituent effects can be transmitted through space (field effects), via conjugative interactions (resonance effects) or by polarization of the styrene π electron system by the polar C—X bond (π polarization effects). The latter effect appears to be more important than previously realized.1H correlations with F and R are used to estimate self-consistent and apparently reasonable Δχ values for C≡N and C≡C—H groups and F and R values for carbonyl substituents and (CH3)3M substituents (M = Si, Ge, Sn, and Pb). The halogens give anomalous results. A comparison of various correlations suggests that these anomalies are magnetic in origin.

scholarly journals Effect of substituents on the 13C-NMR chemical shifts of 3-methylene-4-substituted-1, 4-pentadienes - Part I

2003 ◽  
Vol 68 (2) ◽  
pp. 67-76 ◽  
Author(s):  
Natasa Valentic ◽  
Zeljko Vitnik ◽  
Sergei Kozhushkov ◽  
Majere de ◽  
Gordana Uscumlic ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Heat Of Formation ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
The One ◽  
Semi Empirical

The principles of linear free energy relationships were applied to the 13C substituent chemical shifts (SCS) of the carbon atoms in the unsaturated chain of 3-methylene-4-substituted-1,4-pentadienes. Correlations of the SCS with the substituent parameters of Swain and Lupton provide a mutually consistent picture of the electronic effects in these compounds. The pattern of the electronic effects can be fully rationalized by a model based on the direct transmission of substituent effects through-space (direct through-space field effects), and via conjugative interactions (resonance effects), or by substituent-induced polarization of the ?-system in the unsaturated chain (?-polarization effect). Semi-empirical MNDO-PM3 calculations suggest the s-cis conformation of 3-methylene-4-substituted-1,4-pentadienes as the one with minimal heat of formation.

Transmission of substituent effects in N-(p-substituted phenyl)-phthalimides

1990 ◽  
Vol 55 (1) ◽  
pp. 261-272 ◽  
Author(s):  
Miroslav Holík ◽  
Božena Matějková
Keyword(s):  
Conformational Changes ◽  
Nmr Spectra ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Principal Component ◽  
Electronic Effects ◽  
Diamagnetic Anisotropy ◽  
Electronic Effects Of Substituents ◽  
C Nmr

Chemical shifts of benzene part of the title compounds have been correlated with substituent chemical shifts (SCS) increments a for 1H and z for 13C NMR spectra. These correlations gave pieces of information not only about the through-conjugation of substituents but also about the change of the twist about the central N-C bond with the change of substituent in the para-position. In such a way the electronic effects of substituents have been studied together with the effects due to conformational changes which manifest themselves with the change in the van der Waals repulsion and/or diamagnetic anisotropy of double bond. Chemical shifts in phthalimide part of molecule have been related to the electronic effect of distant substituent after separation of the main source of variation from random error by principal component analysis.

Electronic effects of halogen-substituted methyl groups

1980 ◽  
Vol 33 (6) ◽  
pp. 1291 ◽  
Author(s):  
CW Fong
Keyword(s):  
Benzene Ring ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Methyl Groups ◽  
Electronic Effects ◽  
Substituted Toluenes ◽  
Molecular Deformations

The electronic effects of the halogen-substituted methyl groups, CHnX3-n, where X is F, Cl, Br or I, have been examined by 13C n.m.r, spectroscopy in a series of α-halogen-substituted toluenes. The substituent chemical shifts of all carbon atoms, as well as the σI and σR0 substituent parameters derived from a dual substituent parameter (DSP) analysis, are examined in terms of hyperconjugative and π-inductive substituent effects. Bulky CHnX3-n substituents cause molecular deformations of the benzene ring, consequently invalidating the derivation of substituent parameters from a DSP analysis.

13C Chemical shifts for 4-substituted phenylvinyl ethers, sulfides, and selenides: evidence concerning the relative abilities of O, S, and Se to transmit electronic effects

1977 ◽  
Vol 55 (3) ◽  
pp. 536-540 ◽  
Author(s):  
William F. Reynolds ◽  
Robert A. McClelland
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
13C Chemical Shifts ◽  
Link Group ◽  
Relative Ability ◽  
Link Atom

13C chemical shifts for β carbons of 4-substituted phenylvinyl ethers, sulfides, and selenides plus previous data for styrenes indicate that the relative ability of link groups to transmit electronic effects between conjugative groups is S > Se ≈ — > O (where — refers to no link group, i.e. styrene). However, marked deviations from additivity are noted for C(1) chemical shifts which may indicate that O deactivates the ring to electronic substituent effects while S and Se activate the ring. If this explanation is valid then the actual ability of the link atom to transmit electronic effects is — > O > S > Se.

Carbon-13 chemical shifts as a probe for conformational and electronic effects in alkyl vinyl ethers

1983 ◽  
Vol 61 (3) ◽  
pp. 488-493 ◽  
Author(s):  
John G. K. Webb ◽  
David K. Yung
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Vinyl Ethers ◽  
Resonance Effects ◽  
Polarization Mechanism ◽  
Chemical Shift Data ◽  
Vinyl Group ◽  
The Relationship ◽  
Geminal Substituent

The principle of additivity of substituent chemical shifts (SCS) is applied to the carbon-13 chemical shifts of β carbons (δβ) in a number of 1,1-disubstituted ethylenes and propenes, which includes some α-substituted alkyl vinyl ethers. An additivity relationship is observed for 34 compounds that indicates an independent polarization mechanism across the double bond for each geminal substituent. Positive deviations from additivity are observed for compounds bearing bulky substituents. The magnitude of deviations is taken as an indication of the severity of steric interactions among substituents.Reductions in efficiency of transmission of substituent effects in ring substituted α-phenyl alkyl vinyl ethers, relative to para-substituted styrenes, are interpreted as the result of a variable dihedral angle between the ring and vinyl group. An explanation of the relationship between conformation and transmission of substituent effects is presented as an alternative to existing views. An angular dependence of π-polarization and resonance effects is consistent with the chemical shift data.

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