ISSN:
0749-1581
Keywords:
Tungsten(II) hydrido-pyrazolylborate complexes
;
183W-1H long-range shift correlation
;
1H NOESY
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
183W NMR spectra for several tungsten carbonyl complexes were recorded using heteronuclear multiple-quantum spectroscopy. The measurements involved the use of both one-bond and long-range coupling constants, with the latter technique demonstrating a general approach to obtaining 183W spectra in Tp′ [Tp′ = tris(3,5-dimethylpyrazolyl)borohydride] and Cp tungsten compounds. Differences in the 183W chemical shifts between the Tp′ and Cp complexes are explained in terms of σ-donor and π-acceptor capabilities of the ligands. It is suggested that the very small 1J(183W,1H) value of 7 Hz in WH(Tp′)(CO)3 arises from an interaction of an H+ with a [W(Tp′)(CO)3]- orbital with a relatively large d-component. For WH(Tp′)(CO)(PHC≡CMe) (3), the very lowfield hydride chemical shift, δ = 10.8, is suggested to arise, in part, from anisotropic effects. 1H NOESY measurements on 3 show that the hydride lies in a deshielding region with respect to both the acetylene and two pyrazolylborate rings, the acetylene is bent such that the CH3 and Ph groups move toward one another and there is a second isomer of 3, presumably related to the geometry of the coordinated acetylene with respect to the W—C≡O bond.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260310112
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