Phosphorous Substituted Carbodiimides

The first phosphorus substituted carbodiimide was synthesized by Kohler and Kotte in 

The authors assumed that the molecules had a cyanamid structure. The correct carbodiimide structure was elucidated later. Solid carbodiimide modified phosphates are 

Phosphorous substituted carbodiimides are less stable than most of the other carbodiimides. For example, the carbodiimides Ph2P(0)N=C=NR cannot be distilled without decomposition. However, carbodiimides (Et0)2P(0)N=C=NR can be purified by vacuum distillation. 

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Phosphorous substituted carbodiimides 4 are synthesized by dehydrosulfurization of the corresponding thioureas 3 with HgO. ... 

The silver salt of cyanamide reacts with BrFaP or Ph2P(X)Cl to give bis-phosphorous substituted carbodiimides. For example, a 52 % yield of bis(difluorophosphinyl)carbodiimide 12 is obtained from the silver salt of cyanamide and bromodifluorophosphine. ... 

The reaction of bis(trimethylsilyl)carbodiimide with P(S)P3 at 140-150 °C gives 35 % of the mono phosphorous substituted carbodiimide 20. ... 

The remaining chapters are carbodiimides with unsaturated substituents, halogenated carbodiimides, acyl-, thioacyl- and imidoylcarbodiimides, silicon substituted carbodiimides, nitrogen substituted carbodiimides, phosphorous substituted carbodiimides, sulfur substituted carbodiimides, metal substituted carbodiimides, cyclic carbodiimides, polymeric carbodiimides and application of carbodiimides. 

Carbodiimides are a unique class of reactive organic compounds having the heterocumu-lene structure R—N=C=N—R. They can be formally considered to be the diimides of carbon dioxide or the anhydrides of 1,3-substituted ureas, and they are closely related to the monoimides of carbon dioxide, the isocyanates. The substituent R can be alkyl, aryl, acyl, aroyl, imidoyl or sulfonyl, but nitrogen, silicon, phosphorous and metal substituted carbodiimides are also known. The unsubstituted carbodiimide HN=C=NH is isomeric with cyanamide, H2NCN. Mono substituted carbodiimides, generated in the thermolysis of 1-substituted tetrazoles, can be isolated at liquid nitrogen temperature but isomerize to the cyanamides at higher temperatures. ... 

The reaction of phosphorous substituted carbonimidoyl dichlorides 10 with arylamines in the presence of triethylamine affords the corresponding carbodiimides 11. The reaction proceeds via the intermediate chloroformamidines. The dehydrochlorination of the intermediate chloroformamidine occurs in diethyl ether at room temperature. 

The oxygen in the free hydroxyl groups of diesters of phosphoric acid has been specifically analyzed by Dostrovsky and Halmann (1956) by condensation with tolyl carbodiimide. The substituted urea formed is separated and purified. On heating a sample (30 mg.) to 320°C. with copper bronze powder (1 mg.), carbon dioxide is evolved which contains the oxygen of the free hydroxyl groups of the phosphate. This method is fully described by Halmann (1959) and can presumably be used with monoesters of phosphoric acid and with various phosphonic and sulfonic acids. (See also Pinchas et al., 1962.)... 

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