Carbon-13 shielding effects in metal-alkyl, metal-olefin, and metal-allyl bonds

Cooper, David G.; Hughes, R. P.; Powell, John Wesley

doi:10.1021/ja00781a054

Cited by 45 publications

(8 citation statements)

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“…For complexes 1-7, the high field resonances of their 13C nmr spectra were assigned on the basis of their relative in- Table I. I3C Shieldings" for the Complexes CODPt(CH3)R [1][2] and [CODPt(CHs)L] +PF6- [3][4][5][6][7] Com-Platinum--COD- CDCla 538 (±2) 10 (±2) 18 (±2) 120 (±2) 35 (±2)…”

Section: Resultsmentioning

confidence: 99%

Carbon-13 nuclear magnetic resonance studies of organometallic compounds. VII. 1,5-Cyclooctadieneplatinum(II) derivatives

Chisholm¹,

Clark²,

Manzer³

et al. 1975

J. Am. Chem. Soc.

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Section: Resultsmentioning

confidence: 99%

Carbon-13 nuclear magnetic resonance studies of organometallic compounds. VII. 1,5-Cyclooctadieneplatinum(II) derivatives

Chisholm¹,

Clark²,

Manzer³

et al. 1975

J. Am. Chem. Soc.

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“…Recently, this shielding has also been invoked to interpret 13C shifts in Pd and Pt olefin complexes. 25 It might be expected that superimposed upon this shift would be some details of electron density changes at carbon. Mn(I) should produce less shielding at carbon than Cr(0) because the more electropositive element will have a counteracting deshielding effect by withdrawing electrons from the ring.…”

Section: Resultsmentioning

confidence: 99%

Electronic effects in (CH3)nC6H6-nMn(CO)3+ complexes (n = 0-6) as evidenced by proton and carbon-13 NMR spectroscopy, manganese-55 NQR [nuclear quadrupole resonance] spectroscopy, and carbonyl ir spectroscopy

Brill¹,

Kotlar²

1974

Inorg. Chem.

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A spectroscopic analysis of electronic effects and transmission of electron density in (CH3)"C6H6_rtMn(CO)3+ complexes in = 0-6) using 'H and 13C nmr of the aromatic ring atoms,55Mn nqr spectroscopy, and CO ir spectroscopy is reported. The nmr data for the complexes show substantial shielding of the ring nuclei compared to the free arenes, and this was ascribed to magnetic anisotropy of the ring caused by the metal. By comparison of the Mn(I) complexes to the isoelectronic Cr(0) systems, it was concluded that much more ring -> metal electron migration occurs with Mn(I) than Cr(0). The S5Mn nqr frequencies increase linearly with the number of methyl groups on the ring. The CSHS~ligand appears to be a much better electron donor than CSH6 based on the nqr spectra. Crystal lattice differences produced only 3% change in the 55Mn coupling constant for a series of five anions in the C6H6Mn(CO)3* salts. A larger effect (8%) was observed for the mesitylene salts. Only minute perturbations occur to the axial symmetry of the metal-ring bond in all salts as evidenced by small asymmetry parameters. The carbonyl ir frequencies show a linear correlation with ring substitution, and it is concluded that the electron density changes on the metal are transmitted in a corresponding fashion to the CO groups. All spectra are found to be internally consistent.

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“…Salomon and Kochi (1974) analysed qualitatively the respective effects of u-bonding and nbackbonding on the 13C chemical shift and showed that the backbonding component will always result in an upfield effect while for the bonding component both upfield (decreased u character, increased orbital excitation energy) and downfield (decreased electron density) effects play a role. The alternative explanation given by Cooper et al (1972) for the shielding effect observed for Pd(I1) and Pt(I1) is probably not valid for metals like Cu(I), Ag(1) and Au(1).…”

Section: Spectroscopic Investigationsmentioning

confidence: 92%

“…I7C NMR spectroscopy has also been used extensively to investigate olefin-metal complexes in more detail (Parker and Roberts, 1970;Beverwijk and van Dongen, 1972;Cooper et al, 1972;van Dongen and Beverwijk, 1973;Michel et af., 1974;Salomon and Kochi, 1974). The olefinic carbons of olefins are considerably shielded upon coniplexation with silver(1).…”

Section: Spectroscopic Investigationsmentioning

confidence: 99%

Factors involved in the high pressure liquid chromatographic separation of alkenes by means of argentation chromatography on ion exchangers: Overview of theory and new practical developments

Beek

Subrtova

1995

Phytochemical Analysis

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The literature on the use and theory of silver(I) complexation (argentation) chromatography is reviewed. Apolar isomeric alkenes, for example numerous terpenes and fatty acids, can be well resolved by means of high pressure liquid chromatography on cation exchange materials coated with silver(I) ions, but unfortunately the mechanism on which these separations are based is not fully understood. As part of an attempt to provide a predictive model for the separation of volatile alkenes, the retention of more than 40 C2‐C10 olefins besides a number of C14‐pheromones and volatile terpenes is given and the results discussed. The separation is mainly governed by the type and number of double bonds (isolated, conjugated or aromatic), their steric accessibility (number and size of substituents) for complexation with silver(I) ions, the relief of inherent strain upon complexation and electron donating or withdrawing groups, or polar groups close to the double bond. Polar groups such as hydroxyls also complex weakly with silver. Other functional groups, including carbonyls, and the overall polarity of the solute play only a minor role. Similarly most solvents have only a limited influence on the selectivity and speed of separation, and function more as a transportation medium as in gas chromatography. A comparative model which gives semi‐quantitative estimations of the retention time of most volatile olefins in methanol is presented. Substituent parameters (Ags) which quantitatively forecast the influence of different alkyl side chains are part of this model.

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Carbon-13 shielding effects in metal-alkyl, metal-olefin, and metal-allyl bonds

Cited by 45 publications

References 0 publications

Carbon-13 nuclear magnetic resonance studies of organometallic compounds. VII. 1,5-Cyclooctadieneplatinum(II) derivatives

Carbon-13 nuclear magnetic resonance studies of organometallic compounds. VII. 1,5-Cyclooctadieneplatinum(II) derivatives

Electronic effects in (CH3)nC6H6-nMn(CO)3+ complexes (n = 0-6) as evidenced by proton and carbon-13 NMR spectroscopy, manganese-55 NQR [nuclear quadrupole resonance] spectroscopy, and carbonyl ir spectroscopy

Factors involved in the high pressure liquid chromatographic separation of alkenes by means of argentation chromatography on ion exchangers: Overview of theory and new practical developments

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