1887

n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Karakterisering van Grubbs-tipe-prekatalisatore met behulp van kernmagnetieseresonansiespektrometrie - original research

Volume 38 Number 1
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173

Abstract

Sedert die ontdekking van die ruteniumbevattende prekatalisatore, Grubbs 1 (1) en Grubbs 2 (2), is ’n toename in die ontwikkeling van soortgelyke prekatalisatore getoon. Daar is egter nie met die karakterisering van die prekatalisatore met behulp van kernmagnetieseresonansiespektrometrie (KMR) tred gehou nie. Die gerapporteerde KMRanalises en -karakterisering is meestal tot 1H-, 31P-, COSY-analise beperk met seldsame vermelde 13C-analise. Die hoë natuurlike isotoopvoorkoms van 1H- en 31P-kerne, 99.98% en 100% onderskeidelik, is ’n bydraende faktor tot die vinnige en eenvoudige opname van hierdie spektra. Die leemte in literatuurdata en- opnameparameterstelle aangaande 13C-KMR-analise, word aan die lae natuurlike isotoopvoorkoms van 13C-kerne (1.10%) en die ingeperkte stabiliteit van die katalisatore in oplossing toegeskryf.

In hierdie ondersoek is prekatalisator 1 gebruik om ’n KMR-parameterstel te ontwikkel. Daarna is twee verdere kommersiële Grubbs-tipe-prekatalisatore, 2 en 3, met behulp van hierdie KMR-parameterstel geanaliseer. Die KMR-spektra is weens die lang opnametyd en die onstabiliteit van die prekatalisatore in oplossing in drie stappe opgeneem. Eerstens, is 1H-, COSY-, HSQC- en HMBC-spektra opgeneem, wat altesaam vier ure geduur het. Tweedens, is DEPT135-spektra opgeneem, wat drie ure in beslag geneem het. Laastens is die 13C-spektra opgeneem waarvoor 7 ure in beslag geneem is.

Die KMR-parameterstel wat vanaf die kommersiële prekatalisatore afgelei is, is gevolglik aangewend om ses verdere gesintetiseerde, nie-kommersiële Grubbs-tipeprekatalisatore, 4 tot 9, gedeeltelik te karakteriseer. Deur die voorkoms van oorvleuelende pieke in die aromatiese en alifatiese gebiede is die spektrumresolusie verlaag. Gevolglik is die volledige karakterisering nie moontlik gemaak nie.



Characterisation of Grubbs-type precatalysts with nuclear magnetic resonance spectrometry: Since the discovery of the ruthenium-based precatalysts (1) and (2), an increase in the development of similar precatalysts has been observed. However, the nuclear magnetic resonance (NMR) spectroscopic characterization of these precatalysts could not parallel the development in the field. The NMR analyses and characterisation, reported in the literature, is limited to 1H, 31P, COSY and in rare cases 13C analyses. The ease and short duration of the spectral recording of 1H and 31P nuclei are ascribed to their high, natural isotope abundance of 99.98% and 100% respectively. The lack of reported 13C NMR data of these precatalysts is attributed to the low natural isotope abundance of 13C-nuclei (1.10%) and the observed instability of the catalysts in solution. In this investigation, precatalyst 1 was employed to determine a NMR parameter set, after which two additional commercial Grubbs-type precatalysts, 2 and 3, were analysed with the deduced NMR parameter set. The obtained peak shift values were compared with literature reported values. The excessive recording time and the instability of the precatalysts in solution necessitated recording the NMR spectra in three steps. Firstly, the 1H, COSY, HSQC and HMBC spectra were recorded over a total duration of four hours. Secondly, DEPT135-spectra were recorded, over a period of three hours. Lastly, the 13C-spectra were recorded over seven hours.

Subsequently, the developed NMR parameter set was applied to partially elucidate the structure of six synthesised, non-commercial Grubbs-type precatalysts, 4 to 9. The overlapping peaks, in the aromatic and aliphatic regions of the spectra, decreased the resolution and consequently hampered total structure elucidation.

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/content/journal/10520/EJC-16140178c9
2019-01-01
2019-10-18

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