Accessing heavy allyl-analogous [(TerN)2E]− (E = Sb, Bi) ions and their reactivity towards ECl3

The attempted preparation of the biradicaloid [E(μ-NTer)]2 (E = Sb, Bi) yielded salts of the anion [(TerN)2E]−. These heteroatom allyl analogues could be further utilized in the reaction with pnictogen(III) chlorides to form the first 1,3-dichloro-1-bisma-3-stiba-2,4-diazane [ClSb(μ-NTer)2BiCl]

Reduction of dichloro(diaza-phospha)stibanes – isolation of a donor-stabilized distibenium dication

A reaction of antimonytrichloride SbCl3 with potassium bis(terphenylimino)phosphide K[(TerN)2P] smoothly afforded a novel class of mixed diazadipnictanes, namely dichloro(diaza-phospha)stibane [Ter2N2P(III)Sb(III)Cl2], which is considered to exist as open chain-like and cyclic isomers in an equilibrium. [Ter2N2PSbCl2] is a versatile starting material for reduction and halide abstraction experiments. Halide abstraction led to the formation of a cyclic diazastibaphosphenium cation [P(μ-NTer)2SbCl]+. Upon reduction of [Ter2N2PSbCl2], the transient existence of the novel mixed biradicaloid [P(μ-NTer)2Sb] was proven by a trapping experiment with an alkyne, while reduction in the absence of trapping agents afforded the eight-membered heterocycle [Sb2-{μ-(TerN)2P}2]. This constitutional isomer of a dimerized biradicaloid features a bonding situation that indicates the presence of a donor-stabilized [Sb2]2+ ion

Low temperature isolation of a dinuclear silver complex of the cyclotetraphosphane [ClP(μ-PMes*)]2

The reaction of the cyclotetraphosphane [ClP(μ-PMes*)]2 (1, Mes* = 2,4,6-tri-tert-butylphenyl) with Ag[Al(ORF)4] (RF = CH(CF3)2) resulted in a labile, dinuclear silver complex of 1, which eliminates AgCl above −30 °C. Its properties were investigated by spectroscopic methods, single crystal X-ray diffraction and DFT calculations

On New Staudinger Type Reactions of Phosphorus Centered Biradicaloids, [P(μ-NR)]2 (R = Ter, Hyp), with Ionic and Covalent Azides

Phosphorus centered biradicaloids of the type [P(μ-NTer)]2 [R = Ter = terphenyl = 2,6-bis(2,4,6-trimethylphenyl)phenyl, Hyp = tris(trimethylsilyl)silyl] were treated with covalent (R-N3) and ionic azides (AgN3 and Hg(N3)2). While the reaction with the ionic azides led exclusively to the formation of diazides, [N3P(μ-NTer)]2, triaza-diphospha-pentadienes, RN=P–N(R')–P=NR, were observed in the reaction with covalent azides featuring a Staudinger type reaction followed by PN bond rearrangement reactions. This new Staudinger type mechanism as well as the structure, bonding and thermodynamics along different reaction paths are discussed based on DFT computations

Methyl 5-chloro-2-hydr­oxy-3-(4-methoxy­phen­yl)-4,6-dimethyl­benzoate

In the title compound, C17H17ClO4, the dihedral angle between the mean planes of the two benzene rings is 65.92 (5)°. The methyl ester group lies within the ring plane [deviations of O atoms from the plane = −0.051 (2) and 0.151 (2) Å] due to an intra­molecular O—H⋯O hydrogen bond. In the crystal, mol­ecules are held together by rather weak non-classical inter­molecular C—H⋯O hydrogen bonds, resulting in dimeric units about inversion centers, forming eight- and ten-membered ring systems as R 2 2(8) and R 2 2(10) motifs

Cycloaddition of Alkenes and Alkynes to the P-centered Singlet Biradical [P(μ-NTer)]2

The reaction of biradical [P(μ-NTer)]2 (1, Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl) towards different alkenes (R = 2,3-dimethyl–butadiene, 2,5-dimethyl-2,4-hexadiene, 1,7-octadiene, 1,4-cyclohexadiene) and alkynes (R = 1,4-diphenyl-1,3-butadiyne) was studied experimentally. Although these olefins can react in different ways, only [2+2] cycloaddition products (1R) were observed. The reaction with 2,3-dimethylbutadiene also led to the [2+2] product (1dmb). Thermal treatment of 1dmb above 140 °C resulted in the recovery of biradical 1 upon homolytic bond cleavage of the two P–C bonds and the release of 2,3-dimethylbutadiene. In contrast to this reaction, all other [2+2] additions products (1R, R = 1,7-octadiene, 1,4-cyclohexadiene, 1,4-diphenyl-1,3-butadiyne) began to decompose at temperatures between 200 °C and 300 °C. Only unidentified products were obtained but no temperature-controlled equilibrium reactions were observed. Computations were carried out to shed light into the formal [2+2] as well as the possible [4+2] addition reaction

Azadiphosphaindane-1,3-diyls: A Class of Resonance-Stabilized Biradicals

Conversion of 1,2-bis(dichlorophosphino)benzene with sterically demanding primary amines led to the formation of 1,3-dichloro-2-aza-1,3-diphosphaindanes of the type C6H4(μ-PCl)2N-R. Reduction yielded the corresponding 2-aza-1,3-diphosphaindane-1,3-diyls (1), which can be described as phosphorus-centered singlet biradical(oid)s. Their stability depends on the size of the substituent R: While derivatives with R=Dmp (2,6-dimethylphenyl) or Ter (2,6-dimesitylphenyl) underwent oligomerization, the derivative with very bulky R=tBuBhp (2,6-bis(benzhydryl)-4-tert-butylphenyl) was stable with respect to oligomerization in its monomeric form. Oligomerization involved activation of the fused benzene ring by a second equivalent of the monomeric biradical and can be regarded as formal [2+2] (poly)addition reaction. Calculations indicate that the biradical character in 1 is comparable with literature-known P-centered biradicals. Ring-current calculations show aromaticity within the entire ring system of 1. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH Gmb

Salts of HCN-Cyanide Aggregates : [CN(HCN)2]− and [CN(HCN)3]−

Although pure hydrogen cyanide can spontaneously polymerize or even explode, when initiated by small amounts of bases (e.g. CN−), the reaction of liquid HCN with [WCC]CN (WCC=weakly coordinating cation=Ph4P, Ph3PNPPh3=PNP) was investigated. Depending on the cation, it was possible to extract salts containing the formal dihydrogen tricyanide [CN(HCN)2]− and trihydrogen tetracyanide ions [CN(HCN)3]− from liquid HCN when a fast crystallization was carried out at low temperatures. X-ray structure elucidation revealed hydrogen-bridged linear [CN(HCN)2]− and Y-shaped [CN(HCN)3]− molecular ions in the crystal. Both anions can be considered members of highly labile cyanide-HCN solvates of the type [CN(HCN)n]− (n=1, 2, 3 …) as well as formal polypseudohalide ions. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

Regioselective Suzuki–Miyaura Cross-Coupling Reactions of the Bis(triflate) of 1,4-Dihydroxy-9H-fluoren-9-one

1,4-Diaryl-9H-fluoren-9-ones were prepared by regioselective Suzuki–Miyaura cross-coupling reaction of the bis(triflate) of 1,4-dihydroxy-9H-fluoren-9-one. The reactions proceeded with excellent site selectivity. The first attack occurs at position 1, due to electronic reason

Synthetic strategies to bicyclic tetraphosphanes using P1, P2 and P4 building blocks

Different reactions of Mes* substituted phosphanes (Mes* = 2,4,6-tri-tert-butylphenyl) led to the formation of the bicyclic tetraphosphane Mes*P4Mes* (5) and its unknown Lewis acid adduct 5·GaCl3. In this context, the endo–exo isomer of 5 was fully characterized for the first time. The synthesis was achieved by reactions involving “self-assembly” of the P4 scaffold from P1 building blocks (i.e. primary phosphanes) or by reactions starting from P2 or P4 scaffolds (i.e. a diphosphene or cyclic tetraphosphane). Furthermore, interconversion between the exo–exo and endo–exo isomer were studied by 31P NMR spectroscopy. All compounds were fully characterized by experimental as well as computational methods