77Se couplings

An experimental determination of the spin density distribution in these complexes was recently reported, based on EPR data on 77Se-enriched (at 100%) diselenolene analogs where the 77Se coupling constants and g tensors could be determined from frozen solutions spectra [60]. A 14% spin density was determined on each Se atom in 77Se-enriched [CpNi(bds)] while a larger 16% spin density on... 

Vicinal l3C,77Se coupling constants of between 28 and 39 Hz have been observed in Z-configurated selenoimidates, which contrast to values lower than 10 Hz in the respective. E-isomers302. 

DMSO-4 solvent. b 13C-77Se coupling constant for C-2 = -136.7 Hz (77JOC3725). 

The radicals S3 and Se3 , which are isostructural with PF2, have been detected in alkali halides doped with sulfur or selenium, the identification being based upon the appearance of two different or 77Se coupling constants (Table VII). Because of sign ambiguity in the tensor, two sets of data result. However, we favor set (ii) because we expect the spin-density on the central atom to be less than that on the corresponding oxy-radicals SOo" and Se02". 

The coupling of the selone to racemic carboxylic acids with dicyclohexylcarbodiimide in dichloromethane with 4-dimethylaminopyridine at 0°C for 0.5-1 hour affords the acylated derivatives. Similar results are obtained using the acid chloride and triethyl amine. Figure 13 (upper part) shows the selenium spectrum for the diastereomeric. Y-acyl derivatives of the oxazo-lidine-2-selone with (A,A)-5-methylheptanoic acid. Clearly the shift difference of about (5 = 0.1 is sufficient for integration of the two singlets. The lower part of the figure shows the remarkably different 77Se resonances observed for four species derived from partially deuterated phenylacetic acid. The diastereomeric mixture of the monodeuteriated substance is easily detected (AS = 0.07, 5.0 Hz). 

An on line dialysis flow system coupled to ICP-MS (VG Plasma Quad PQII, Thermo Elemental, Winsford, Chaeshire, UK) has been employed to determine trace elements in serum samples by IDMS. Isotope dilution was performed on samples incubated with enriched 65Cu, 66Zn, 77Se and 206Pb for 24 h at 36 °C prior to dialysis to quantify total element concentrations.60... 

The mode of attachment of the [M(CO)s] fragment to the 1,2,4-selenadiphosphole ring was established as being via the phosphoms P-2 atom bonded directly to selenium. The 31P NMR spectrum of both compounds 19 and 34 shows a pattern of lines typical for an [AB] spin system with satellites due to further coupling to the 77Se nucleus. Additional... 

Se NMR spectra of selenadiphospholes and diselenaphospholes 44, 45, 78, and 47 were reported (Table 25) <2002CEJ2705>. In compounds 44, 45, 78, and 47, the exocyclic selenium atom is at lower frequency relative to those within the heterocycle. A l/(Se,Se) coupling of 271 Hz is characteristic of compound 45. In molecule 47, the ring atom Se-3 has a 2/(P,Se) coupling to the phosphorus(v) center P-1 of 20 Hz. On the other hand, there is no resolved coupling between the exocyclic Se-1 and the internal phosphorus(m) center P-2. 

Table 25 Chemical shift 8 (ppm) and coupling constants J (Hz) for 77Se NMR spectra of compounds 44, 45, 78, and 47a,b ...

The 31P 1H -NMR spectrum of compound 26 shows a singlet (S 388 ppm) exhibiting 77Se-satellites, with a coupling constant (2/PSe = 88 Hz) whose magnitude is typical for a two-bond phosphorus-selenium coupling <2003JOM(672)1>. 

Key Words High-resolution NMR, INADEQUATE, ADEQUATE, Carbon-carbon coupling constants, Long-range couplings, Double-quantum coherence, 13C NMR, 15N NMR, 29Si NMR, 77Se NMR, Fullerenes, Polymers, Review. 

The NMR spectrum of selenophene (Fig. 2) shows spin-spin interaction of 77Se with the a protons, the coupling constant, J77Sc H being 22.5 Hz. 

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