Stable Cubic Phosphorus‐Containing Radicals

Armstrong, Andrea; Chivers, Tristram; Parvez, Masood; Boeré, René T.

doi:10.1002/anie.200353108

Cited by 78 publications

(53 citation statements)

References 25 publications

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“…The difference in appearance between this EPR spectrum and that of 3a in THF (Figure 3) can be attributed in large part to the presence of the higher-spin nucleus 127 I. As was observed previously for 3a, 14 the EPR spectrum of 3c in hexane (see Supporting Information) is not dependent upon sample concentration, though significant line broadening occurs (vide supra) even for extremely dilute solutions. This spectrum can be simulated accurately using HFCCs (Table 4) which are quite similar to those used to simulate the EPR spectrum of 3c in THF, confirming that this radical retains its cubic structure in the non-coordinating solvent hexane.…”

Section: The Structures Of the Distorted-cubic Model Radicals {Li2[p(supporting

confidence: 73%

“…14,15 The remarkable stability of these radicals can be attributed to the delocalization of spin density over two or four nitrogen atoms, respectively, as well as the presence of bulky isopropyl or tert-butyl substituents to impede their reactivities.…”

Section: Bmentioning

confidence: 99%

“…Initial studies 14 of 3b and 3c indicated that the EPR spectra of these two radicals are dependent on both temperature and sample concentration. At extreme dilution, distortions in the EPR spectrum of 3b had been suggested to result from disruption of the cubic framework to form a monocyclic radical; alternatively, it is conceivable that a mixture of paramagnetic species is present in solution.…”

Section: Bmentioning

confidence: 99%

“…However, conclusive evidence that 3b exists as a cube at this concentration has been obtained previously in the form of a low-temperature EPR spectrum, which clearly indicated HFCCs to three equivalent 14 N atoms. 14 The limiting EPR spectrum of 3b in THF (ca. 1.5 mM), which was reported in a preliminary communication, 14 does not display the obvious inversion symmetry that is characteristic of a single paramagnetic species in solution and is observed in the EPR spectra of both 3a and 3d.…”

Section: The Structures Of the Distorted-cubic Model Radicals {Li2[p(mentioning

confidence: 99%

“…14 The limiting EPR spectrum of 3b in THF (ca. 1.5 mM), which was reported in a preliminary communication, 14 does not display the obvious inversion symmetry that is characteristic of a single paramagnetic species in solution and is observed in the EPR spectra of both 3a and 3d. This spectral distortion, indicating the presence of a second paramagnetic species in solution, supports the hypothesis that at extreme dilution in THF, partial dissociation of the cubic framework of 3b occurs, presumably due to THFsolvation of the lithium cations (Scheme 1).…”

Section: The Structures Of the Distorted-cubic Model Radicals {Li2[p(mentioning

confidence: 99%

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Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)₃(NR‘)]^•^2-

et al. 2005

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The reaction of Cl 3 PNSiMe 3 with 3 equiv of LiHNR (R ) i Pr, Cy, t Bu, Ad) in diethyl ether produces the corresponding tris(amino)(imino)phosphoranes (RNH) 3 PNSiMe 3 (1a, R ) i Pr; 1b, R ) Cy; 1c, R ) t Bu; 1d, R ) Ad); subsequent reactions of 1b−d with n BuLi yield the trilithiated tetraimidophosphates {Li 3 [P(NR) 3 (NSiMe 3 )]} (2a, R ) Cy; 2b, R ) t Bu; 2c, R ) Ad). The reaction of [( t BuNH) 4 P]Cl with 1 equiv of n BuLi results in the isolation of ( t BuNH) 3 PN t Bu (1e); treatment of 1e with additional n BuLi generates the symmetrical tetraimidophosphate {Li 3 [P(N t Bu) 4 ]} (2d). Compounds 1 and 2 have been characterized by multinuclear ( 1 H, 13 C, and 31 P) NMR spectroscopy; X-ray structures of 1b,c were also obtained. Oxidations of 2a−c with iodine, bromine, or sulfuryl chloride produces transient radicals in the case of 2a or stable radicals of the formula {Li 2 [P(NR) 3 (NSiMe 3 )]LiX•3THF} • (X ) Cl, Br, I; R ) t Bu, Ad). The stable radicals exhibit C 3 symmetry and are thought to exist in a cubic arrangement, with the monomeric LiX unit bonded to the neutral radical {Li 2 [P(NR) 3 (NSiMe 3 )]} • to complete the Li 3 N 3 PX cube. Reactions of solventseparated ion pair {[Li(THF) 4 ]{Li(THF) 2 [(µ-N t Bu) 2 P(µ-N t Bu) 2 ]Li(THF) 2 } (6) with I 2 or SO 2 Cl 2 produce the persistent spirocyclic radical {(THF) 2 Li(µ-N t Bu) 2 P(µ-N t Bu)Li(THF) 2 } • (10a); all radicals have been characterized by a combination of variable concentration EPR experiments and DFT calculations.

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Section: The Structures Of the Distorted-cubic Model Radicals {Li2[p(supporting

confidence: 73%

Section: Bmentioning

confidence: 99%

Section: Bmentioning

confidence: 99%

Section: The Structures Of the Distorted-cubic Model Radicals {Li2[p(mentioning

confidence: 99%

Section: The Structures Of the Distorted-cubic Model Radicals {Li2[p(mentioning

confidence: 99%

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Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)₃(NR‘)]^•^2-

et al. 2005

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Stable Radicals of the Heavy p‐Block Elements

Konu

Chivers

2010

Stable Radicals

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Cyclische Gruppe‐15‐Radikalkationen

et al. 2015

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Biradikaloide Cyclo-1,3-dipnikta-2,4-diazan-1,3diyle des Typs [E(m-NTer) 2 E] (2,E=P, As,T er = 2,6-Dimesitylphenyl) wurden mit Silbersalzen schwachkoordinierender Anionen wie [AgL n ][B(C 6 F 5 ) 4 ]( L = Donormolekül) monooxidiert, um neue cyclische Radikalmonokationen,[ E(m-NTer) 2 E] +· (3 + C), zu erzeugen. Wenn kleinere und basischere Anionen im Silbersalz vorhanden sind, werden die Anionen kovalent an den Radikalzentren gebunden, und die Reaktion führt zu Dipniktadiazanen, [FP(m-NTer) 2 PF] (5)u nd [(CF 3 CO 2 )P(m-NTer) 2 P(CF 3 CO 2 )].E ine Zwei-Elektronen-Oxidation des Biradikaloids zum Dikation [E(m-NTer) 2 E] 2+ wurde nicht beobachtet. Theoretische Studien und EPR-Daten belegen, dass die Spindichte fast ausschließlich auf den schweren Pniktogenen Ed es vormaligen Biradikaloids lokalisiert ist. Die Bindungssituation der Radikalkationen weist eine seltene transannulare Ein-Elektronen-p-Bindung ohne s-Bindung auf.Stabile und transiente Radikale von Hauptgruppenelementen finden in jüngerer Zeit großes Interesse.Ü bersichtsartikel zu diesem Thema wurden durch Power [1] und, mit dem Schwerpunkt auf Carben-substituierten Radikalen, von Bertrand et al. [2] verçffentlicht. Ausgewählte Beispiele für Bor-, [3][4][5][6] Kohlenstoff-, [7,8] Stickstoff-, [9] Phosphor- [10,11] und Silicium-zentrierte [12,13] Radikale kçnnen in der Literatur gefunden werden. Jüngst berichteten Beckmann et al. über die Oxidation von Dichalkogeniden und die anschließende Isolierung von Radikalkationen. [14] Unser Interesse besteht besonders an Radikalen, die auf Elementen der Gruppe 15 zentriert sind, von denen auch einige Beispiele bekannt sind (Schema 1). Durch thermische Bindungsspaltung oder -bildung konnte die Erzeugung bzw. Rekombination von P-zentrierten Radikalen in mehreren Fällen von Diphosphanen und entsprechend auch bei den schweren Homologen beobachtet werden (A). [15][16][17][18][19][20] Durch sterisch anspruchsvolle Substituenten konnten Radikale,d ie durch die Oxidation von Triarylphosphanen, [21] Te traaryldiphosphanen [22] und Phosphaalkenen [23] erzeugt wurden, an der Dimerisierung gehindert werden. Dipniktene wurden reduziert, sodass Radikalanionen (B)e rhalten wurden, während Dipniktane zu Radikalkationen oxidiert wurden (C und D). [24,25] Carben-substituierte Radikale wurden von Erst kürzlich wurde von Grützmacher et al. über die Herstellung der Carben-substituierten P 3 -u nd PA sP-Radikale (E)b erichtet. [30] Radikalspezies,d ie das Diphosphacyclobutan als zentrales Strukturmotiv aufweisen, wurden von Ito,Y oshifuji et al. untersucht, [31,32] während Wang et al. cyclische Diphosphadiazane und Te traphosphane oxidieren konnten (G, H). [33] Kürzlich berichtete unsere Gruppe über verschiedene offenschalige Gruppe-15-Singulett-Biradikaloide (2), die durch die Reduktion entsprechender Dichlordipniktadiazane Schema 1. Ausgewählte stabile Gruppe-15-Radikale.

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Stable Cubic Phosphorus‐Containing Radicals

Cited by 78 publications

References 25 publications

Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)₃(NR‘)]^•^2-

Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)₃(NR‘)]^•^2-

Stable Radicals of the Heavy p‐Block Elements

Cyclische Gruppe‐15‐Radikalkationen

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Stable Cubic Phosphorus‐Containing Radicals

Cited by 78 publications

References 25 publications

Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)3(NR‘)]•2-

Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)3(NR‘)]•2-

Stable Radicals of the Heavy p‐Block Elements

Cyclische Gruppe‐15‐Radikalkationen

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Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)₃(NR‘)]^•^2-

Cubic and Spirocyclic Radicals Containing a Tetraimidophosphate Dianion [P(NR)₃(NR‘)]^•^2-