Symmetry-Amplified J Splittings for Quadrupolar Spin Pairs: A Solid-State NMR Probe of Homoatomic Covalent Bonds
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- 作者：Fr茅d茅ric A. Perras ; David L. Bryce
- 刊名：Journal of the American Chemical Society
- 出版年：2013
- 出版时间：August 28, 2013
- 年：2013
- 卷：135
- 期：34
- 页码：12596-12599
- 全文大小：277K
- 年卷期：v.135,no.34(August 28, 2013)
- ISSN：1520-5126
文摘
Chemically informative J couplings between pairs of quadrupolar nuclei in dimetallic and dimetalloid coordination motifs are measured using J-resolved solid-state NMR experiments. It is shown that the application of a double-quantum filter is necessary to observe the J splittings and that, under these conditions, only a simple doublet is expected. Interestingly, the splitting is amplified if the spins are magnetically equivalent, making it possible to measure highly precise J couplings and unambiguously probe the symmetry of the molecule. This is demonstrated experimentally by chemically breaking the symmetry about a pair of boron spins by reaction with an N-heterocyclic carbene to form a 尾-borylation reagent. The results show that the J coupling is a sensitive probe of bonding in diboron compounds and that the J values quantify the weakening of the B鈥揃 bond which occurs when forming an sp2鈥搒p3 diboron compound, which is relevant to their reactivity. Due to the prevalence of quadrupolar nuclei among transition metals, this work also provides a new approach to probe metal鈥搈etal bonding; results for Mn2(CO)10 are provided as an example.