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Die im Titel genannte Achtringverbindung 6 stellt ein Analogon zum Octaphenyl‐cyclotetraphosphazen dar, in dem zwei gegenüberliegende Stickstoff‐Ringglieder durch zweifach‐koordinierten Phosphor ersetzt sind. Sie ist aus (Ph2P)2NLi und P4 zugänglich und wird von sehr starken Nucleophilen an den PP‐Bindungen angegriffen und im Sinne einer Syntheseumkehr abgebaut. Sie wird selektiv am zweifach‐koordinierten Phosphor methyliert und bildet mit PdCl2 und PtCl2 durch Koordination dieser Phosphorglieder cis‐Chelate. Die Strukturen von 6 und des PdC12‐Komplexes 8 wurden röntgenographisch bestimmt und ermöglichen eingehende Strukturvergleiche. Insgesamt ergibt sich bei aller Cyclophosphazen‐Ähnlichkeit ein phosphidischer Charakter des zweifach‐koordinierten Phosphors in 6. Eine MNDO‐Berechnung bestätigt das ebenfalls.

Salicylic aldehyde (2a) adds to 2-methyl-5-phenyl-2H-compound forms dimers by a double hydrogen bond bet-1,2,4,3-triazaphosphole (1) to yield the bicyclic phosphonic ween two HN-PO units. Substituted salicylic aldehydes as amide 3a. The OH group adds to the P=N bond, the carbon well as ortho-hydroxyacetophenone and benzophenone reatom of the carbonyl group is inserted into the other P-N act in the same way. bond, and the phosphorus atom is oxidized. In the crystal the The phosphorus atom of a 2H-1,2,4,3-triazaphosphoIe such as 1 [1,2] is capable of both accepting and donating a pair of electrons. As a consequence it adds alcohols and other protic nucleophiles to its P = N bond and is oxidized by sulfur or halogen. Alcohols or phenols with appropriate additional functions can at the same time make use of both triazaphosphole reactivities. Glycols, 2-azido alcohols or oheterodienylphenols thus yield spirocyclic phosphorane~[~I. Salicylic aldehyde offers itself as another possible difunctional partner, although the nature of its second function is different. For the reaction with the triazaphosphole phosphorus atom it provides a nucleophilic hydroxyl and an electrophilic carbonyl group at a suitable three-bond distance. Results and DiscussionFrom the benzene solution of 2-methyl-5-phenyl-2H-1,2,4,3-triazaphosphole (1) and the 2-hydroxybenzaldehydes 2a-d (R' = H, R2-R5 = H, OMe, NOz) or 2-hydroxyacetophenone (2e) (R1 = Me, R2-R5 = H) or 2-hydroxybenzophenone (20 (R' = Ph, R2-R5 = H) products 3a-f precipitate. They are colorless except for the orangeyellow nitro derivative 3d. The reaction requires several days at ambient temperature for completion and of course proceeds more rapidly under reflux conditions. The compounds 3 consist of an equimolar combination of the two components as revealed by elemental analysis. It turned out, however, that the product in this case is not a spirocyclic A single-crystal X-ray analysis (see below) revealed the structure of example 3a. The NMR spectra of all other products (Tables 1 and 2) also correspond to those of 3a.The phenolic oxygen atom is bound to the phosphorus atom as expected, and the phosphorus atom is oxidized[*]X-ray structure analysis.

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