Safety note: Some of the materials mentioned here are very dangerous. Ask a qualified chemist for advice before handling them. Qualified chemists should check the relevant safety literature before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are flammable. Specifically, cadmium is a toxic carcinogen: wear protective gloves. Dimethyl cadmium is volatile: wear protective clothing and work in a hood. Latex gloves do not provide protection.

Cadmium NMR

Cadmium has two NMR active spin ½ nuclei, ¹¹¹Cd and ¹¹³Cd, that yield narrow signals (fig. 1) over a wide chemical shift range. ¹¹³Cd is very slightly the more sensitive nucleus and is therefore usually the preferred nucleus. Cadmium NMR is used for the study organocadmium compounds, cadmium complexes, inorganic cadmium and cadmium binding to proteins and other molecules of biological interest.

Fig. 1. Comparison of the (proton decoupled) NMR spectra of the cadmium isotopes ¹¹¹Cd and ¹¹³Cd in neat dimethyl cadmium

Each type of cadmium compound has its characteristic chemical shift range (fig. 2).

Fig. 2. Chemical shift ranges for cadmium NMR

Both cadmium nuclei couple to other nuclei. ¹H, ¹³C, ³¹P and ⁷⁷Se couplings have been reported. On the coupling nucleus two set of couplings are observed as satellites as in the ¹³C spectrum in fig. 3. One bond couplings to ¹³C are typically around 500 Hz with the ¹¹¹Cd coupling slightly smaller than the ¹¹³Cd coupling.

Fig. 3. ¹³C-NMR spectrum of Me₂Cd showing coupling to both cadmium nuclei

Two and three bond couplings to ¹H are typically in the region of 50 Hz. The difference between the ¹¹¹Cd and ¹¹³Cd coupling constants with ¹H is small so appear merged in the spectrum in fig. 4.

Fig. 4. ¹H-NMR spectrum of Me₂Cd showing apparently a single coupling to both cadmium nuclei

Resolution enhancment sepearates the two couplings (fig. 5).

Fig. 5. ¹H-NMR spectrum of Me₂Cd showing separate couplings to each cadmium nucleus

¹¹¹Cadmium NMR

(¹¹¹Cd) ¹¹¹Cadmium is slightly less sensitive than ¹¹³Cd so is not usually the preferred nucleus of cadmium. It is a spin ½ nucleus and yields sharp signals (fig. 6).

Fig. 6. ¹¹¹Cd-NMR spectrum of neat dimethyl cadmium showing coupling to ¹³C as satellite signals

Cadmium often shows couplings to other nuclei, ¹H, ¹³C, ¹⁹F, etc. Cadmium couplings to protons can be removed by decoupling as in fig. 6. The coupled spectrum of dimethyl cadmium (fig. 7) shows a two bond coupling to ¹H, (²J_111Cd,H) of 49.6 Hz.

Fig. 7. ¹¹¹Cd-NMR spectrum of neat dimethyl cadmium showing coupling to ¹H

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Properties of ¹¹¹Cd

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¹¹³Cadmium NMR

(¹¹³Cd) ¹¹³Cadmium is slightly more sensitive than ¹¹¹Cd so is usually the preferred nucleus of cadmium. It is a spin ½ nucleus and yields sharp signals (fig. 8).

Fig. 8. ¹¹³Cd-NMR spectrum of neat dimethyl cadmium showing coupling to ¹³C as satellite signals

Cadmium often shows couplings to other nuclei, ¹H, ¹³C, ¹⁹F, etc. Cadmium couplings to protons can be removed by decoupling as in fig. 8. The coupled spectrum of dimethyl cadmium (fig. 9) shows a two bond coupling to ¹H, (²J_113Cd,H) of 51.9 Hz.

Fig. 9. ¹¹³Cd-NMR spectrum of neat dimethyl cadmium showing coupling to ¹H

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Properties of ¹¹³Cd

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References

1. G. E. Maciel and M. Borzo, "High resolution cadmium-113 nuclear magnetic resonance by pulse Fourier transform", J. Chem. Soc., Chem. Comm., 394 (1973).
2. C. J. Turner and R. F. M. White, "Heteronuclear magnetic double-resonance studies of cadmium-113 shielding in dialkyl cadmium compounds", J. Magn. Res., 26, 1-5 (1977).
3. I. M. Armitage and Y. Boulanger, "Cadmium-113 NMR", NMR Newly Accessible Nucl., 2, 337-365 (1983).
4. J. L. Sudmeier, J. L. Evelhoch, S. J. Bell, M. C. Storm and M. F. Dunn, "Cadmium-113 NMR studies of insulin and calmodulin", Dev. Biochem., 14, 235-237 (1980).
5. G. K. Carson and P. A. W. Dean, "A selenium-77 and cadmium-113 NMR spectroscopic study of phenylselenolate complexes of cadmium", Inorg. Chim. Acta, 66, 37-39 (1982).
6. P. F. Rodesiler and E. L. Amma, "The solid and solution cadmium-113 NMR spectra of six and seven coordinate cadmium dications: relevance to calcium-substitution proteins", J. Chem. Soc., Chem. Comm., 182-184, (1982).
7. Y. Boulanger, I. M. Armitage, K. A. Miklossy and D. R. Winge, "Cadmium-113 NMR study of a metallothionein fragment. Evidence for a two-domain structure", J. Biol. Chem., 257, 13717-13719 (1982).
8. Structure elucidation of the metal-binding sites in metallothionein by cadmium -113 NMR. Armitage, Ian M.; Otvos, James D.; Briggs, Richard W.; Boulanger, Yvan. Dep. Mol. Biophys. Biochem., Yale Univ., New Haven, CT, USA. Federation Proceedings (1982), 41(13), 2974-80.
9. P. Gettins and J. E. Coleman, "Cadmium-113 nuclear magnetic resonance of cadmium (II) alkaline phosphatases", J. Biol. Chem., 258, 397-407 (1983).
10. J. K. Nicholson, P. J. Sadler, K. Cain, D. E. Holt, M. Webb and G. E. Hawkes, "88 MHz cadmium-113 NMR studies of native rat liver metallothioneins", Biochem. J., 211, 251-255 (1983).
11. Cadmium-113 NMR. Armitage, Ian M.; Boulanger, Yvan. Dep. Mol. Biophys. Biochem., Yale Univ., New Haven, CT, USA. Editor(s): Laszlo, Pierre. NMR Newly Accessible Nucl., 2, 337-65 (1983).
12. I. G. Dance, "Applications of cadmium NMR to polycadmium complexes. II. [Cd_x(SPh)_y]^2x-y species in solution in relation to metallothionein aggregates", Inorg. Chim. Acta, 108, 227-230 (1985).
13. I. G. Dance, "Applications of cadmium NMR to polycadmium complexes. III. Effects of zinc/cadmium and selenium/sulfur substitution in the tetraadamantanoid cage [S₄Cd₁₀(SPh)₁₆]^4- in relation to heterometal metallothioneins", Aust. J. Chem., 38, 1745-1755 (1985).
14. I. G. Dance, R. G. Garbutt and D. C. Craig, "Applications of cadmium NMR to polycadmium complexes. IV. Reactions of [Cd₁₀(SCH₂CH₂OH)₁₆]⁴⁺ with chloride ion, and the crystal and molecular structure of hexadeca(2-hydroxyethanethiolato)tetrachlorodecacadmium [Cd₁₀(SCH₂CH₂OH)₁₆Cl₄]", Aust. J. Chem., 39, 1339-1463 (1986).
15. M. A. Kennedy and P. D. Ellis, "Cadmium-113 nuclear magnetic resonance spectroscopy of Cd²⁺-substituted heme and myoglobin", J. Am. Chem. Soc., 111, 3195-3203 (1989).
16. J. E. Coleman, "Cadmium-113 nuclear magnetic resonance applied to metalloproteins", Methods in Enzymology, 227 (Metallobiochemistry, Pt. D) 16-43 (1993).
17. F. He, X. Mao, "Study of the coordination sites of histidine to cadmium (II)", Bopuxue Zazhi, 13, 25-34 (1996).

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