Some applications of multinuclear NMR

Abstract

This work makes use of the rapidly expanding technique of Fourier Transform Nuclear Magnetic Resonance (FT-NMR) Spectroscopy to study a number of different areas of chemistry. Work was carried out into the study of new pulse sequences, and composite pulses, to improve the observing conditions for low frequency nuclei. These techniques were applied to the study of ⁷³Ge NMR, a spin ⁹/₂ nucleus of low resonance frequency. The polarisation transfer pulse sequence INEPT has found considerable use in ¹³C NMR but is less widely used for other nuclei, despite its inherent advantages. This sequence was used in a ²⁹Si NMR study to determine the ²J coupling constants of compounds in the series Mec₍₄₋ₓ₎Si(GeH₃)ₓ (x = 1,2,3). Inversion of peaks as a result of the INEPT sequence help clarify the couplings in this twelve spin system. ¹¹B NMR was used to study the adducts formed by the reaction of the boron trihalides BCl₃, BBr₃, and BI₃ with the donors PPh₃, NPh₃, and AsPh₃. Other techniques have not been able to provide a clear picture of what is happening in these reactions, but NMR has provided a much clearer picture. Unfortunately it has not provided a definite answer on the pathway of halogen exchange within the adducts formed. Another system undergoing halogen exchange was also studied, this time using ¹¹⁰Sn NMR. In the reactions of Et₄NSnX₃ with Y₃SnCo(CO)₄ (X,Y = Cl, Br) a crystal structure of the products could not be refined because of disorder in the halogen atoms. While other techniques were able to show that a number of different species existed in solution ¹¹⁹Sn NMR was able to show what these species were and was able to indicate the amount of each existing in solution.