This microreview describes progress in the development and coordination chemistry of donor‐functionalized phosphinines – the phosphorus analogues of pyridines – that has been made during the last five years. The stepwise assembly of 2,4,6‐triarylphosphinines starting from functionalized benzaldehyde and acetophenone derivatives allows the incorporation of additional substituents into specific positions of the aromatic phosphorus heterocycle. This strategy can be used to synthesize chelating phosphinines, which is an essential aspect especially for the preparation of phosphinine‐based transition metal complexes containing metal centres in medium‐to‐high oxidation states. Access to such coordination compounds used to be very difficult because monodentate phosphinines cannot be used for this purpose, due to their weak σ‐donor properties but strong π‐accepting capacities. Moreover, metal complexes of less highly substituted phosphinines turned out to be extremely sensitive to nucleophilic attack, making their straightforward synthesis, characterization and application rather unattractive. The recent strategies in this area facilitate synthetic access to a completely new set of phosphinine‐metal complexes for the first time, leading to a much broader scope for potential applications. New developments in the areas of homogeneous catalysis and materials sciences can consequently be foreseen in the near future.
This highlight review provides an overview of recent developments in the chemistry of pyridyl-functionalized λ 3 σ 2 -phosphinines and 3H-1,2,3,4-triazaphospholes. The access to novel chelating, low-coordinate phosphorus heterocycles can lead to a much broader scope for potential applications. New developments in areas such as homogeneous catalysis, molecular materials, and supramolecular chemistry can consequently be foreseen in the near future.
A hitherto unprecedented electronic situation has been observed for a substituted, pyridyl-functionalized phosphinine. In contrast to previous studies, this compound shows considerable π-donor properties as the result of the rather strong +M effect of the CH3S-substituent, changing the electronic properties of this low-coordinate and aromatic phosphorus heterocycle substantially.
To facilitate the use of biomethane in existing transmission and distribution infrastructures, CEN/TC 408 developed specifications (EN 16723) for injecting biomethane into the natural gas grids and using it as a transport fuel. Currently, the test methods cited in EN 16723 lack metrological aspects and have not been specifically developed for biomethane. To address this need, ISO/TC193/SC1/WG25 “Biomethane” has been created to work on standardized methods. To assess conformity of biomethane with the specification and to provide essential input to WG25, test methods are being developed in this research for a group of impurities such as siloxanes, halogenated volatile organic compounds, hydrogen chloride, hydrogen fluoride. A further objective of this research is to develop fit-for-purpose measurement standards for these parameters, to enable SI-traceable calibration and facilitate accurate measurement results. An overview of the progress made with respect to the development of measurement standards and test methods for trace level concentrations of impurities is presented, with a focus on static measurement standards of siloxanes and halogenated volatile organic compounds, dynamic gas standards of HCl and HF, as well as corresponding test methods based on gas chromatography and spectroscopic techniques. The work presented is pivotal for the development of metrological infrastructure for biomethane conformity assessment.
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