Paramagnetic pyrazolylborate complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR spectra and first-principles studies of chemical shifts
Pyykkönen, Ari; Feher, Robert; Köhler, Frank H.; Vaara, Juha (2020-06-19)
Pyykkönen, A., Feher, R., Köhler, F. H., & Vaara, J. (2020). Paramagnetic Pyrazolylborate Complexes Tp2M and Tp*2M: 1H, 13C, 11B, and 14N NMR Spectra and First-Principles Studies of Chemical Shifts. Inorganic Chemistry, 59(13), 9294–9307. https://doi.org/10.1021/acs.inorgchem.0c01176
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see [insert ACS Articles on Request author-directed link to Published Work, see https://doi.org/10.1021/acs.inorgchem.0c01176.
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https://urn.fi/URN:NBN:fi-fe2020081961116
Tiivistelmä
Abstract
The paramagnetic pyrazolylborates Tp₂M and Tp*₂M (M = Cu, Ni, Co, Fe, Mn, Cr, V) as well as [Tp₂M]+ and [Tp*₂M]+ (M = Fe, Cr, V) have been synthesized and their NMR spectra recorded. The ¹H signal shift ranges vary from ∼30 ppm (Cu(II) and V(III)) to ∼220 ppm (Co(II)), and the ¹³C signal shift ranges from ∼180 ppm (Fe(III)) to ∼1150 ppm (Cr(II)). The ¹¹B and ¹⁴N shifts are ∼360 and ∼730 ppm, respectively. Both negative and positive shifts have been observed for all nuclei. The narrow NMR signals of the Co(II), Fe(II), Fe(III), and V(III) derivatives provide resolved ¹³C,¹H couplings. All chemical shifts have been calculated from first-principles on a modern version of Kurland–McGarvey theory which includes optimized structures, zero-field splitting, and g tensors, as well as signal shift contributions. Temperature dependence in the Fe(II) spin-crossover complex results from the equilibrium of the ground singlet and the excited quintet. We illustrate both the assignment and analysis capabilities, as well as the shortcomings of the current computational methodology.
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