An Unusual Isomerization to Tetraazastiboles

Abstract

Dedicated to Professor Peter Klüfers on the occasion of his 60th birthdayPentazoles are aromatic molecules consisting of a fivemembered nitrogen-atom ring (Scheme 1), one of which is bonded to a hydrogen atom (HN 5 ) or an organic substituent (RN 5 ; R is usually an aryl group). They form a class of highly endothermic and explosive compounds. The existence of an all-nitrogen aromatic azole ring, RN 5 (R = C 6 H 5 ), was considered by Clusius and Hurzeler [1] and shown by Huisgen and Ugi [2] in the reaction of phenyldiazonium chloride, [C 6 Substitution of one nitrogen atom in pentazoles by a heavier element of Group 15 leads to isovalent tetraazapnictoles (Scheme 1), RN 4 E (E = P, As, Sb, Bi), which also have electronic structures that are related to those of aromatic hydrocarbons with (4n + 2)p electrons.[3] Only recently, two examples of tetraazapnictoles (E = P, R = Mes* = 2,4,6-tritert-butylphenyl or m-Ter = 2,6-bis(2,4,6-trimethylphenyl)-phenyl;[4a, 5] E = As, [6] R = Mes*) have been isolated and fully characterized. Two different synthetic routes to tetraazapnictoles have been described: [4,6]

Low‐Temperature Isolation of the Bicyclic Phosphinophosphonium Salt [Mes*2P4Cl][GaCl4]

“…[1][2][3] In particular,( pseudo)halogen-substituted cyclic dipnictadiazanes (B,Scheme 1) proved to be versatile starting materials for the synthesis of (transient) compounds with NPn multiple bonds (for example, A)g enerated by cycloreversion reactions, [4][5][6][7][8] larger ring systems by subsequent cycloaddition reactions or ring expansion, [4,9,10] as well as cationic species which are formed by abstraction of halogen atoms (C). [1][2][3] In particular,( pseudo)halogen-substituted cyclic dipnictadiazanes (B,Scheme 1) proved to be versatile starting materials for the synthesis of (transient) compounds with NPn multiple bonds (for example, A)g enerated by cycloreversion reactions, [4][5][6][7][8] larger ring systems by subsequent cycloaddition reactions or ring expansion, [4,9,10] as well as cationic species which are formed by abstraction of halogen atoms (C).…”

“…Ring systems composed of Group 15 elements (pnictogens, Pn) are af ascinating aspect of main-group chemistry. [1][2][3] In particular,( pseudo)halogen-substituted cyclic dipnictadiazanes (B,Scheme 1) proved to be versatile starting materials for the synthesis of (transient) compounds with NPn multiple bonds (for example, A)g enerated by cycloreversion reactions, [4][5][6][7][8] larger ring systems by subsequent cycloaddition reactions or ring expansion, [4,9,10] as well as cationic species which are formed by abstraction of halogen atoms (C). [11][12][13][14][15] In this regard, we are currently interestedinthe reactivity of analogous ring systems solely based on phosphorus (that is, [XP(m-PR)] 2 )t oe valuate possible reaction routes to similar, unprecedented phosphorus species.F or example,r eports of cationic phosphorus ring systems include phosphinophosphonium frameworks (I-III,S cheme 2), [16][17][18][19][20] related cyclic and bicyclicpolyphosphorus frameworks (V, VI) [21] and, in awider sense,s everal cluster cations (IV), [22][23][24][25] as well as bicyclic systems with cationic substituents.…”

A Bismuth–Arene σ‐Complex – On the Edge of Menshutkin‐Type Complexes

“…Since all attempts to synthesize the desired RN 4 Bi heterocycle using inter molecular [3+2] cycloaddition reactions failed, we changed our approach to intra molecular cycloaddition reactions. In analogy to the synthesis of tetrazastiboles, attempts were made to synthesize various azido derivatives of 1 , which might be isomerized to a tetrazabismuthole by Lewis‐acid induced Me 3 SiCl elimination and subsequent intramolecular [3+2] cycloaddition. For this reason, 1 was treated with NaN 3 in thf to generate the azido‐chloride or the diazido substituted compounds Mes*N(SiMe 3 )Bi(Cl)N 3 and Mes*N(SiMe 3 )Bi(N 3 ) 2 .…”

“…The aim of these investigations was the synthesis of a bismadiazonium salt (R‐N≡Bi + ) and a tetrazabismuthole (R‐N 4 Bi) in a formal [3+2] cycloaddition reaction with a covalently bound azide, R‐N 3 . Tetrazapnictoles (R‐N 4 Pn, Pn = element of group 15 = pnictogen) are already known for the lighter congeners of bismuth (Pn = P, As, and Sb) . The formation of such compounds includes Me 3 SiX (X = Cl, [OTf]; OTf = OSO 2 CF 3 ) elimination and cyclisation reactions with azides (Scheme ).…”

Tieftemperatur‐Isolierung des bicyclischen Phosphinophosphoniumsalzes [Mes*2P4Cl][GaCl4]

“…B. A), [4][5][6][7][8] grçßeren Ringsystemen durchC ycloadditionsreaktionen sowie Ringerweiterung [4,9,10] oder auch kationischen Spezies durch Abstraktion von Halogenen (C). [11][12][13][14][15] Infolgedessen interessieren wir uns momentan für die Chemie analoger Ringsysteme,d ie ausschließlich aus Phosphor aufgebaut sind (d. h. [XP(m-PR)] 2 ), um mçgliche Reaktionswege zu vergleichbaren, neuen Phosphorspezies aufzufinden.…”