Die Darstellung von 1,1,3,3,5,5‐Hexakis(dimethylamino)‐λ5‐[1,3,5]triphosphinin (4) und der Bildungsweg aus Methyl‐bis(dimethylamino)difluorophosphoran (1) und n‐Butyllithium werden beschrieben. Das chemische Verhalten der Verbindungen des Typs [R2P=CH–]n wird mit dem der isoelektronischen Dichlorphosphazene [Cl2P=N–]n verglichen. Die Struktur von 4 wird durch NMR‐Spektren und eine Kristallstrukturanalyse belegt.

Ylidylphosphorus Sulfides, Selenides, Disulfides, Sulfide Selenides, and Diselenides We report on the first stable monomeric phosphorus mono‐chalcogenides 2, 8 and the first stable dichalcogenides 4, 10 without bulky or intramolecularly coordinating substituents. They are stabilized by a high contribution of the zwitterionic resonance formula, which follows both from the NMR spectra and from an X‐ray structure determination. Their preparation starts from triphenylphosphoniumylidyl‐dichlorophosphanes 1. For the monochalcogenides they are treated with sodium sulfide or selenide or better with bis(trimethylsilyl) sulfide or selenide. In case of the C‐phenyl and C‐meta‐tolyl representatives and also of the C‐trimethylsilyl compound a number of secondary, partly novel products are obtained. – The dichalcogenides result from the reaction with sodium disulfide and diselenide, respectively, or from the oxidation of the monochalcogenides. – Alkylation of the monochalcogenides results in ylidylalkylchalcogenophosphenium salts 13, 15. In solution they are in equilibrium with more or less of the covalent form 14, 16, depending on the anion and on the solvent. Alkylation is often accompanied by secondary reactions. A diselenide loses selenium on alkylation.

The cyclotrimethylenetriphosphinic acid (1), isoelectronic to the cyclotriphosphoric acid, is formed in the hydrolysis of 1,1,3,3,5,5-hexakis(dimethylamino)-1λ ,3λ ,5λ -[1,3,5]triphosphinine. Compound 1 is stable to acids and bases. On heating for a longer period of time in D O each of the three methylene groups is monodeuterated.

Diphosphabenzole. VII [1]Reaktionen von 1,1,3,3-Tetrakis(dimethylamino)-1 k 5 , 3 k 5 -diphosphet mit 5-Cyano-1-pentin und mit 2-(Cyanmethyl)-1-methylpyrrol Inhaltsu È bersicht. 5-Cyano-1-pentin reagiert mit der a È quimolaren Menge des k 5 -Diphosphets 1 zum k 5 -Diphosphinin (k 5 -Diphosphabenzol) (3), mit der doppelt a È quimolaren Menge 1 zum k 5 -Diphosphinin (4). 2-(Cyanmethyl)-1-methylpyrrol (5) bildet mit 1 als Hauptprodukt die acyclische Verbindung 6. Die Schmelzpunkte von 4´CH 3 CN und 6 sowie die Massen-, NMR-und IR-Spektren von 3, 4 und 6 werden mitgeteilt. Die Kristallstruktur von 4´CH 3 CN zeigt eine offenkettige ylidische CPCP-Sequenz, die mit dem sechsgliedrigen Heterocyclus eines k 5 -Diphosphinins u È ber eine Ethylenbru È cke verknu È pft ist. Die Kristallstruktur von 6 besta È tigt das Vorliegen eines acyclischen konjugierten Doppelylids. Diphosphabenzenes. VII.Reactions of 1,1,3,3-Tetrakis(dimethylamino)-1 k 5 , 3 k 5 -diphosphete with 5-Cyano-1-pentine and 2-(Cyanomethyl)-1-methylpyrrol Abstract. 5-Cyano-1-pentine reacts with the equimolar amount of the k 5 -diphosphete 1 to give the k 5 -diphosphinine (k 5 -diphosphabenzene) (3), while reaction with the double equimolar amount of 1 yields the k 5 -diphosphinine (4). The acyclic compount 6 is the main product of the reaction between 1 and 2-(cyanomethyl)-1-methylpyrrol, 5. Melting points of 4´CH 3 CN and 6, and mass, nmr and ir spectra of 3, 4, and 6 are reported. The crystal structure of 4´CH 3 CN shows an open-chain ylidic CPCP-sequence, which is linked to a k 5 -diphosphinine via an ethylene bridge. The X-ray structure analysis of 6 confirms the existence as an acyclic conjugated double ylid.Keywords: 1 k 5 ,3 k 5 -diphosphete; 1 k 5 ,3 k 5 -[1,3]diphosphinine; 3,5-diphospha-hexa-2,4-diene nitrile; n.m.r, i.r. spectroscopy; Crystal structure.

No abstract