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End date: 2024 × Start date: 2020 × End date: 2024 × Start date: 2020 × DDC: 540 × Type: article × Publisher: Weinheim : Wiley-VCH × WGL Institute: LIKAT ×

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    On New Staudinger Type Reactions of Phosphorus Centered Biradicaloids, [P(μ-NR)]2 (R = Ter, Hyp), with Ionic and Covalent Azides
    (Weinheim : Wiley-VCH, 2020) Schulz, Axel; Hinz, Alexander; Rölke, Anne; Villinger, Alexander; Wustrack, Ronald
    Phosphorus centered biradicaloids of the type [P(μ-NTer)]2 [R = Ter = terphenyl = 2,6-bis(2,4,6-trimethylphenyl)phenyl, Hyp = tris(trimethylsilyl)silyl] were treated with covalent (R-N3) and ionic azides (AgN3 and Hg(N3)2). While the reaction with the ionic azides led exclusively to the formation of diazides, [N3P(μ-NTer)]2, triaza-diphospha-pentadienes, RN=P–N(R')–P=NR, were observed in the reaction with covalent azides featuring a Staudinger type reaction followed by PN bond rearrangement reactions. This new Staudinger type mechanism as well as the structure, bonding and thermodynamics along different reaction paths are discussed based on DFT computations.
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    Cycloaddition of Alkenes and Alkynes to the P-centered Singlet Biradical [P(μ-NTer)]2
    (Weinheim : Wiley-VCH, 2020) Chojetzki, Lukas; Schulz, Axel; Villinger, Alexander; Wustrack, Ronald
    The reaction of biradical [P(μ-NTer)]2 (1, Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl) towards different alkenes (R = 2,3-dimethyl–butadiene, 2,5-dimethyl-2,4-hexadiene, 1,7-octadiene, 1,4-cyclohexadiene) and alkynes (R = 1,4-diphenyl-1,3-butadiyne) was studied experimentally. Although these olefins can react in different ways, only [2+2] cycloaddition products (1R) were observed. The reaction with 2,3-dimethylbutadiene also led to the [2+2] product (1dmb). Thermal treatment of 1dmb above 140 °C resulted in the recovery of biradical 1 upon homolytic bond cleavage of the two P–C bonds and the release of 2,3-dimethylbutadiene. In contrast to this reaction, all other [2+2] additions products (1R, R = 1,7-octadiene, 1,4-cyclohexadiene, 1,4-diphenyl-1,3-butadiyne) began to decompose at temperatures between 200 °C and 300 °C. Only unidentified products were obtained but no temperature-controlled equilibrium reactions were observed. Computations were carried out to shed light into the formal [2+2] as well as the possible [4+2] addition reaction.