A diphosphine with an unsupported PP bond connecting two carbon‐free “inorganic” 1,3,2,4,5‐diazaphosphadisilolidine rings was prepared by reductive coupling of a P‐chloro‐substituted monocyclic precursor molecule. VT‐EPR studies revealed that the diphosphine exists in solution, like other compounds of this kind, in dynamic equilibrium with the corresponding phosphinyl radicals. Determination of the radical concentration from the EPR spectra permitted to calculate thermochemical parameters for the homolytic PP bond fission. The results disclose that both the enthalpy and entropy of dissociation are higher than in topologically related bi(diazaphospholidines). The impact of the entropy term allows explaining that, regardless of the presence of an energetically rather stable PP bond, the onset of dissociation is observable even at ambient temperature. Irradiation experiments showed that radical formation cannot only be induced thermally, but also by photolysis.

中文翻译：

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带有无机骨架的N-杂环二膦的合成及其热裂解和光裂解

通过还原偶联一个P-氯取代的单环前体分子，制备了一个具有无支撑PP键的二膦连接两个无碳的“无机” 1,3,2,4,5-二氮杂磷二甲硅烷基环。VT-EPR研究表明，与其他此类化合物一样，二膦与相应的次膦酰基基团动态平衡存在于溶液中。由EPR光谱确定自由基浓度可以计算出均相PP键裂变的热化学参数。结果表明，解离的焓和熵都高于拓扑相关的双（二氮杂膦烷）。熵项的影响可以解释为，无论是否存在能量上相当稳定的PP键，即使在环境温度下也可以观察到解离的开始。