Three-membered Rings with Two Heteroatoms including Phosphorus to Bismuth

Weber L. Three-membered Rings with Two Heteroatoms including Phosphorus to Bismuth. In: Katrizky AR, Ramsden CA, Scriven EFV, Taylor RJK, eds. Comprehensive Heterocyclic Chemistry III : a Review of the Literature 1995-2007. Vol. 1. Oxford: Elsevier; 2008: 695-747.The chapter describes the synthesis, structures, bonding, and chemical properties of three-membered ings with two heteroatoms including phosphorus, arsenic, and antimony. Covering the literature of the years between 1996 to 2006 diphosphiranes, diphosphirenes, diphosphirenium- and diphosphirenylium complexes, phosphaarsiranes and phosphastibiranes are discussed. Structural features are elucidated by NMR-data, single crystal X-ray investigations and quantum chemical studies. Thereby the great difference in organonitrogen and organophosphorus chemistry became evident as pointed out in the case of bisphosphino carbenium- and amidinium-ions. Moreover, diphosphirenyl radicals and dimers thereof are without precedence in organonitrogen chemistry. The progress in the chemistry under discussion is to some extend due to the availability of novel appropriately functionalized phosphaalkenes and phosphaalkynes

Cross‐Coupling between Hydrazine and Aryl Halides with Hydroxide Base at Low Loadings of Palladium by Rate‐Determining Deprotonation of Bound Hydrazine

We report the Pd-catalyzed C–N coupling of hydrazine with (hetero)aryl chlorides and bromides to form aryl hydrazines with catalyst loadings as low as 100 ppm of Pd and KOH. Mechanistic studies revealed two catalyst resting states: an arylpalladium(II) hydroxide and arylpalladium(II) chloride. These compounds are present in two interconnected catalytic cycles and react with hydrazine and base or hydrazine alone to give the product. The selectivity of the hydroxide complex with hydrazine to form aryl over diaryl hydrazine was lower than that of the chloride complex, as well as the catalytic reaction. In contrast, the selectivity of the chloride complex closely matches that of the catalytic reaction, indicating that the aryl hydrazine is derived from this complex. Kinetic studies show that the coupling process occurs by rate-limiting deprotonation of a hydrazine-bound arylpalladium(II) chloride complex to give an arylpalladium(II) hydrazido complex