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The synthesis of a new bis‐NHP complex (NHP=N‐heterocyclic phosphenium) of chromium via salt metathesis and studies of its reactivity are reported. Photochemical reactions with H2 and selected olefins give rise to non‐isolable H2‐ and π‐alkene complexes identified spectroscopically, while internal alkynes react via activation of the triple bond to yield isolable metalla‐phospha‐cyclobutenes characterized by spectroscopic and XRD data. DFT studies give a preliminary account of the bonding in H2‐ and alkene‐complexes and explain the different reactivity towards alkenes and alkynes as the consequence of kinetic effects. Photolysis of the bis‐NHP‐complex in the presence of H2 and olefins or alkenes enables the catalytic hydrogenation of the organic substrates, while the π‐ethene complex mediates the catalytic hydrogenation of ethene in a dark reaction. The similarities and differences between both catalytic processes are shortly discussed. [ABSTRACT FROM AUTHOR]

Two N-heterocyclic phosphines with exocyclic SCN substituents were synthesised via metathesis of chlorophosphine precursors with KSCN and fully characterised. The crystallographic studies reveal that the products exhibit pronounced structural differences. The thiocyanato unit binds in one case via the nitrogen atom to yield a molecular structure with a slightly elongated P-N single bond and, in the other case, via the sulfur atom to form a structure that is best described as an ion pair and forms a one-dimensional coordination polymer in the crystal. DFT calculations suggest that the P-N and P-S interactions can be described as covalent and dative bonds, respectively, and that the structural differences correlate with the different cation stabilities of the individual phosphenium cation fragments. Key words: N-heterocyclic phosphines, ambident Lewis bases, dative bonds, coordination isomerism. Nous avons synthétisé deux phosphines N-hétérocycliques portant des substituants SCN exocycliques par voie de métathèse de précurseurs chlorophosphine avec le KSCN, et nous les avons soumis à une caractérisation complète. Les analyses cristallographiques révèlent que les produits présentent des différences structurales importantes. L'unité thiocyanate se lie dans un cas par l'atome d'azote pour produire une structure moléculaire caractérisée par une liaison simple P-N légèrement allongée, et dans l'autre cas, par l'atome de soufre pour former une structure qui s'apparente davantage à une paire d'ions créant un polymère de coordination unidimensionnel dans le cristal. Les calculs DFT indiquent que les interactions P-N et P***S pourraient être décrites comme des liaisons covalentes et bipolaires, respectivement, et que les différences structurales sont corrélées avec la stabilité des différents fragments cationiques de phosphénium. [Traduit par la Rédaction] Mots-clés: phosphines N-hétérocycliques, bases de Lewis ambidentates, liaisons bipolaires, isomérisme de coordination., Introduction The reaction between a Lewis acid (electron pair acceptor) and a Lewis base (electron pair donor) to form a complex (or Lewis pair) is one of the most fundamental [...]

The article titled "Cover Feature: The Noble Addendum of a Phosphenium Ligand to a Base Metal: Coordination, Activation, and Hydrogenation of Alkenes and Alkynes on a Chromium Complex" explores the chemical diversity and reactivity of a bis‐phosphenium complex of chromium. The research focuses on the catalytic hydrogenation of alkenes through two molecular pathways: a photochemical route and a dark reaction. The dark reaction involves a ligand exchange reaction with alkynes, resulting in the production of metallacycles. The article provides further details on these processes and their implications. [Extracted from the article]

P-hydrogen-substituted 1,3,2-diazaphospholenes were prepared by an improved procedure from diazadines. Extensive studies of the reaction behavior confirmed that these compounds behave as molecular hydrides that reduce organic carbonyl compounds and undergo halide/hydride metathesis with halides of various main-group elements.

Ferrocene‐1,1′‐dithiol reacts with PCl3 and P(NMe2)3 to give [3]ferrocenophanes with SPS‐ansa‐bridges comprising potentially reactive P−Cl and P−N bonds at the central bridge atom. The products were characterized by NMR data and single‐crystal XRD studies. The P‐chloro‐derivative exists both in the solid state and in solution as a mixture of two energetically nearly degenerate conformers with different stereochemical disposition of the ansa‐bridge. Activation parameters for the dynamic equilibration between both isomers in solution were determined by dynamic NMR spectroscopy. Computational studies suggest that the isomerization proceeds via a torsional motion of the bridging SPS‐unit rather than via configuration inversion at the phosphorus atom. [ABSTRACT FROM AUTHOR]