2001 structure

structure (organic substances)K 9000

11 - 023Diphosphetes–Substituent Stabilized Ring Systems. — Thepreviously postulated stepwise mechanism of the formation of σ2P,σ4P-1,2-diphosphetes as (I) through reaction of phosphaacetylene with phosphinocarbeneis confirmed by quantum chemical methods.Investigation of different calculatedstructural and electron density related parameters and the molecular orbitalsreveals that electron delocalization plays an important role in the stabilizationof (I) and, thus, affirms the crucial role of the amino (on σ4-P) and thesilyl (on neighbouring C) substituent, which both together increase electrondelocalization. Increasing the valence of the σ2-P atom through substitution,e.g. (II), destabilizes the diphosphete ring, which remains only stable as result ofthe effect of amino and silyl substituents. — (BERTRAND, GUY; EISFELD,WOLFGANG; NYULASZI, LASZLO; REAU, REGIS; REGITZ, MANFRED;SZIEBERTH, DENES; Perkin 2 (2000) 11, 2324-2327; Lab. Chim. Coord.,CNRS, Inst. Natl. Polytech., Univ. Paul Sabatier, F-31077 Toulouse, Fr.; EN)

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