Synthese, Reaktivität und Eigenschaften des sym-Dimethyltetraphenylcarbodiphosphorans

Flosdorf, Kimon

Thesis

Open Access

Synthese, Reaktivität und Eigenschaften des sym-Dimethyltetraphenylcarbodiphosphorans

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dkf.pdf (27.22 MB)

Date

2025-09-12

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Flosdorf, Kimon

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Person

Dehnen, Stefanie

Person

Kuzu, Istemi

Abstract

The synthesis, properties, and reactivity of sym-dimethyltetraphenylcarbodiphosphane {CDP(Me)} were investigated in this work. First, the preparation of CDP(Me) from bis(diphenylphosphino)methane was optimized. Particular attention was paid to the NMR spectra of the (intermediate) products obtained. For this purpose, a method was developed that makes it possible to calculate the non-measurable, virtual coupling constant of the phosphorus atoms approximately. A corresponding calculation program was implemented to enable repeated and practical application of the method. The reactions of CDP(Me) with iodomethane, dimethyl sulfate, and (SiMe3)(OTf) in solution yielded the respective 1:1 compounds {CDP(Me)Me}I, {CDP(Me)Me}(MeSO4), and {CDP(Me)SiMe3}(OTf). In all cases, it was not possible to isolate the 1:2 compound. Mass spectrometric and NMR spectroscopic evidence was found for the successful formation of {CDP(Me)(SiMe3)2}(OTf)2. Reactions of CDP(Me) with PPhClX (X = Ph, Cl) also yielded the 1:1 compound in each case. Attempts to produce a phosphanyliden adduct were unsuccessful. Through the methylation of {CDP(Me)PPh2}Cl, it was possible to produce the triple-symmetric cation {CDP(Me)P(Me)Ph2}. CDP(Me) was reacted with B(C6F5)3 to investigate whether a frustrated Lewis pair (FLP) forms, as is the case for hexaphenylcarbodiphosphorane {CDP(Ph)}. In contrast to the more sterically demanding CDP(Ph), however, the "normal" Lewis acid-base adduct {CDP(Me)B(C6F5)3} was formed. The reactions of CDP(Me) with coin metal halides were investigated. As expected, the reaction with copper(I) chloride yielded [Cu{CDP(Me)}Cl]. Contrary to expectations, the reaction with silver(I) chloride yielded the tricentric complex [Ag{μ2-CDP(Me)}ClAg{μ2-CDP(Me)}AgCl2], in which two CDP(Me) units act as μ2-bridging ligands. To investigate the ability of carbodiphosphoranes to act as 4e− donors, the complex [Fe{CDP(Me)}{N(SiMe3)2}2] was prepared. The complex was investigated with regard to its static magnetic properties using SQUID. Quantum chemical calculations performed on [Fe{CDP(Ph)}{N(SiMe3)2}2] as an example provided evidence for 4e− donation from CDP(Ph). The complex [Ni{CDP(Me)}(CO)3] was obtained by reacting CDP(Me) with nickel tetracarbonyl, which was used to determine the Tolman Electronic Parameter (TEP) and the Percent Buried Volume (%Vbur) of CDP(Me). This reaction also allowed the isolation of the dinuclear complex [Ni2{μ2-CDP(Me)}(CO)4(μ2-CO)]. The molecular structures of all isolatable compounds were determined by single crystal structure analysis. Where possible, all compounds were characterized by mass spectrometry and 1H, 13C, and 31P NMR spectroscopy. The results of this work showed that although the reactivity of CDP(Me) and CDP(Ph) are similar in many respects, there are also striking differences. These differences can be attributed to the greater electron density and lower steric hindrance of CDP(Me).