Radical Reactivity of the Biradical [⋅P(μ-NTer)2P⋅] and Isolation of a Persistent Phosphorus-Cantered Monoradical [⋅P(μ-NTer)2P-Et]

The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ-NTer)₂P⋅] ( 1 ) (Ter=2,6-bis-(2,4,6-trimethylphenyl)-phenyl) is reported, yielding trans-addition products of the type [Br−P(μ-NTer)₂P−R] ( 2 ), so-called 1,3-substituted cyclo-1,3-diphospha-2,4-diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo-1,3-diphospha-2,4-diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in-situ detection of the phosphorus-centered monoradical [⋅P(μ-NTer)₂P-R].< To provide further evidence for the radical mechanism, [⋅P(μ-NTer)₂P-Et] ( 3Et ⋅) was synthesized directly by reduction of the bromoethane addition product [Br-P(μ-NTer)₂P-Et] ( 2 a ) with magnesium, resulting in the formation of the persistent phosphorus-centered monoradical [⋅P(μ-NTer)₂P-Et], which could be isolated and fully characterized, including single-crystal X-ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ-NTer)₂P-Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ-NTer)₂P⋅] ( 1 ) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ-NTer)₂P⋅] with EtBr. In the field of hetero-cyclobutane-1,3-diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P-centered biradicals and P-centered monoradicals in terms of radical reactivity.     

Photochemical Transformations with Iodine Azide after Release from an Ion‐Exchange Resin

This report discloses the photochemical homolytic cleavage of iodine azide after its formation following release from polymer‐bound bisazido iodate(I) anions. A series of radical reactions are reported including the 1,2‐functionlization of alkenes and the unprecedented chemoselective oxidation of secondary alcohols in the presence of primary alcohols.     

Polymerforschung und -technologie im Iran

Im Laufe der letzten Jahre wurden - von den meisten westlichen Fachkollegen unbemerkt - an mehreren iranischen Universitäten und Forschungsinstituten Abteilungen eingerichtet, die sich in Forschung und Lehre mit Chemie, Physik, Anwendungs- und Verfahrenstechnik der Polymere beschäftigen. Das 1986 gegründete Polymer Research Center of Iran organisierte im Mai dieses Jahres das 1. Internationale Seminar.     

On the Influence of the Distortion Distribution on the Determination of Roentgenographic Particle Sizes and Distortions (II) Distortion Distributions and Evaluation Procedure

It is shown that a Gaussian distribution of the distortion not enables in each case an exact evaluation of experimentally measured Debye-Scherrer lines. – After a discussion of simple possibilities for set up of simple and more common distortion distributions with more than one free parameter is given a procedure independent on the distortion distributions for the determination of roentgenographic particle sizes and distortions.     

The crystal structure of 1-anilino-3-phenylimino propene-(1), C15H14N2

The 1-Anilino-3-phenylimino propene-(1) crystallizes in the Iba2 space group having the lattice constants a = 20.132 Å; b = 16.102 Å; c = 7.683 Å. The elementary lattice cell contains 8 molecules. The intensities were measured by means of an automatic fourcircle diffractometer. The structure was clarified by a direct phase determination. The refinement was carried out by means of the least squares method for 1532 symmetryindependent reflections up to an R-value of 0.10. The molecular structure is more similar to that of the asymmetric polymethine merocyanines, and less to the symmetrical polymethine cyanines. This is due to the different electronic structure of the amino and imino groups in the molecule. The molecules are electrically neutral. The intermolecular contacts are made through N-H…N hydrogen bridges and van-der-Waals contacts between C- and H-atoms.