Ein N/P‐Analogon des Cyclotetraphosphazens: Reaktionen und Struktur des Octaphenyl‐1,5,2λ⁵,3,4λ⁵,6λ⁵,7,8λ⁵‐diazahexaphosphocins und seines PdCl₂‐Komplexes

Abstract

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.

Methylation of some cyclic triphosphenium ions

“…As mentioned in the Section Experimental, there were also small amounts of some phosphorus-containing impurities in the starting material for this system. In all of the mixtures except the one derived from dppE (6,12), signals observed late in the reaction sequence between 193.3 and 193.0 ppm suggested the formation of some MePCl 2 [15]. It should be pointed out that in all systems there was some PCl 3 still present even after disappearance of the resonance from the diphosphane starting material.…”

“…Subsequently several other examples have been reported, including ions with a five-membered ring [1][2][3][4][5][6], a six-membered ring [4][5][6][7], two linked six-membered rings [4,7], and a seven-membered ring [5,6], as well as four- [8] and eight-membered neutral species with either one [9,10] or two [11,12] units of three linked phosphorus atoms. The ions are all characterized by a lowfrequency 31 P NMR shift for the central phosphorus atom and a large 1 J PP (>400 Hz) value.…”

Structural and 31P NMR solution studies on some cyclic triphosphenium ions and their 2‐arsa‐analogues

“…Subsequently other triphosphenium cations with a fivemembered ring, a six-membered ring or two linked six-membered rings have been described [3,4], as well as four- [5] and eight-membered ring neutral species with either one [6,7] or two [8,9] units of three linked phosphorus atoms. All of these species showed quite large (250-500 Hz) 1 J P A P B coupling constants.…”

Protonation of some cyclic triphosphenium ions

“…2(a), although the system is delocalized [6,7,[18][19][20][21]. In the protonated derivative, the middle phosphorus P A is expected to become effectively a neutral P(III) species coordinated by two positively charged P B atoms, Fig.…”