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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 [...]

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.

Research was conducted to examine the synthesis of phosphoranylidene carbenoids Mes*-P(=E)=C(X)Li(THF)3 (E = NMes*, C(SiMe3)2; X = Br, Cl, F) and to characterize their molecular structures using low-temperature X-ray diffractometry and multinuclear NMR studies. Results confirm the presence of moomeric molecules with THF-solvated metal atoms in both solution and solid state. NMR studies demonstrate that the dynamic exchange between the two components in solution can be directly monitored in 2D 6Li, 31P shift correlations.

The phosphavinylidene carbenoid DME-solvate (Z)-Mes*-P=C(Cl){Li(DME)2} or the corresponding THF-solvate was distinguished by nuclear magnetic resonance spectroscopy and single-crystal X-ray diffractometry. Carbenoids were believed to be possible building blocks in organic chemistry and exhibit unique bonding capacity. It was observed that the carbenoid complex was a closely bound ion pair with its carbenic core acting mainly as a cryptocarbanion.

The reactivity of the bis(triphenylphosphonio)isophosphindolide triflate was analyzed during the reaction of the bis(phosphonio)isophosphindolide cation with Hg2+. A phosphinito complex was formed by the reaction of the bis(phosphonio)isophosphindolide cation with HgCl2 and H2O or MeOH. The conversion of bis(triphenylphosphonio)isophosphindolide to phosphonium ions also involved 1,1-oxidative additions at the two coordinate phosphorus which was similar to isoelectronic compounds.

The single-crystal X-ray diffraction and solution and solid-state [super 31]P NMR spectroscopy were employed to prepare and characterize a series of P-phospholyl-substituted N-heterocyclic phosphines. The experimental observations and population analysis of computed electron densities classified the P-P bonds in the molecules under study as 'dative' rather than 'normal' covalent bonds and addressed the compounds as hybrids between covalent diphosphines and phosphenium-phospholide contact ion pairs.

NMR studies of diamino phosphenium ions and p-chlorophosphines reactions shows they react via chloride scrambling, and not by the formation of P-P bonded phosphenium-phosphine complexes. A computational study in the gas phase show the formation of halide-bridge adducts is preferred over the energetically less favorable P-P bonded structures.