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Accurate computations of 77Se NMR chemical shifts with the GIAO-CCSD method

✍ Scribed by Michael Bühl; Jürgen Gauss; John F. Stanton

Publisher
Elsevier Science
Year
1995
Tongue
English
Weight
358 KB
Volume
241
Category
Article
ISSN
0009-2614

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✦ Synopsis

Relative NMR chemical shifts (8(Se)) have been computed at the GIAO-MBPT(2) and GIAO-CCSD levels for the selenium-containing compounds H2Se, SeCO and CSe 2. With a large basis set, 775e shifts calculated at the GIAO-CCSD level for these molecules are -335, -468 and 281 ppm, respectively, relative to Me2Se. The results for H2Se and CSe 2 are in good agreement with gas phase NMR measurements of -345 and 243 ppm, while the value for SeCO is close to a value measured in solution (-447 ppm). Correlation contributions to the shielding are severely overestimated at the GIAO-MBPT(2) level; inclusion of higher-order effects such as those included in GIAO-CCSD is essential for a quantitative description of selenium chemical shifts. The 8(Se) value of 2618 ppm predicted for the transient H2C=Se at the GIAO-CCSD level indicates that the selenium nucleus in this molecule is more deshielded than in any other known compound.

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