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This report describes a one‐pot multi‐step procedure to obtain double azahelicenes via nucleophilic fluorine substitution of 2,2‐di(2‐bromophenyl)‐1,1‐difluoroalkenes and palladium‐catalysed ring closing reaction. The developed synthesis approach allows easy diversification of substituents at all four fragments of the obtained X‐shaped aza[4,6]helicene entity. Yields range from 20 % to 60 % among 12 product examples. X‐ray single crystal analysis reveals formation of (P,P) and (M,M) enantiomer mixture of products. Optical and electrochemical properties of selected products were studied by performing UV/Vis absorption, photoluminescence and cyclic voltammetry measurements. Experimental results are supported by (TD)‐DFT, NICS and NICS2BC calculations. [ABSTRACT FROM AUTHOR]

A series of thienoindolizine structural isomers have been synthesized in a one‐pot, two‐step procedure starting from easily accessible gem‐difluoroalkene functionalized bromothiophenes. The developed method gives easy access to a range of thienoindolizine products containing thieno[3,2‐g]‐, thieno[3,4‐g]‐ and thieno[2,3‐g]indolizine core structures. The described synthesis strategy consists of a base mediated, transition metal free nucleophilic substitution of fluorine atoms by nitrogen containing heterocycles followed by a Pd catalyzed intramolecular cyclization. A series of 22 final product examples has been obtained with yields ranging from 29 % to 95 %. UV/Vis absorption, fluorescence spectroscopy, fluorescence lifetime measurements and cyclic voltammetry were carried out with selected final products to evaluate structural effects on photophysical and electrochemical properties. (TD)DFT and NICS calculations were performed to provide insight into the electronic properties of the four core molecular structures. [ABSTRACT FROM AUTHOR]

Differently substituted phenyl isonitriles (with C−H bonds in ortho‐position) and naphthyl isonitriles were reacted with the cyclic biradical [⋅P(μ‐N‐Ter)2P⋅] (1). Insertion of the isonitrile formed a cyclic five‐membered biradical [⋅P(NTer)2C(R)P⋅] (2R, R=phenyl, naphthyl) in the first step, followed by C−H activation at the aryl substituent, resulting in novel azaphospholes (5R), which could be isolated and fully characterized. The formation of the azaphospholes can be prevented by the addition of a second equivalent of isonitrile, which causes the blocking of the radical centers in 2R by adduct formation (3R). Quantum mechanical calculations showed that a significant increase in the aromaticity of the benzo‐ and naphtho‐azaphospholes is one of the driving forces for the activation process leading to the formation of thermodynamically favored azaphospholes. Targeted activation of C−H bonds using biradical systems represents a new synthetic approach to generate benzo‐ and naphtho‐azaphospholes. [ABSTRACT FROM AUTHOR]

The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ‐NTer)2P⋅] (1) (Ter=2,6‐bis‐(2,4,6‐trimethylphenyl)‐phenyl) is reported, yielding trans‐addition products of the type [Br−P(μ‐NTer)2P−R] (2), so‐called 1,3‐substituted cyclo‐1,3‐diphospha‐2,4‐diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo‐1,3‐diphospha‐2,4‐diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in‐situ detection of the phosphorus‐centered monoradical [⋅P(μ‐NTer)2P‐R].< To provide further evidence for the radical mechanism, [⋅P(μ‐NTer)2P‐Et] (3Et⋅) was synthesized directly by reduction of the bromoethane addition product [Br‐P(μ‐NTer)2P‐Et] (2 a) with magnesium, resulting in the formation of the persistent phosphorus‐centered monoradical [⋅P(μ‐NTer)2P‐Et], which could be isolated and fully characterized, including single‐crystal X‐ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ‐NTer)2P‐Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ‐NTer)2P⋅] (1) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ‐NTer)2P⋅] with EtBr. In the field of hetero‐cyclobutane‐1,3‐diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P‐centered biradicals and P‐centered monoradicals in terms of radical reactivity. [ABSTRACT FROM AUTHOR]

The oxidation of silylated hydrazine, (Me3Si)2N−N(H)SiMe3, with silver salts led to the formation of a highly labile hydrazinium‐yl radical cation, [(Me3Si)2N−N(H)SiMe3].+, at very low temperatures (decomposition > −40 °C). EPR, NMR, DFT and Raman studies revealed the formation of a nitrogen‐centered radical cation along the N−N unit of the hydrazine. In the presence of the weakly coordinating anion [Al{OCH(CF3)2}4]−, crystallization and structural characterization in the solid state were achieved. The hydrazinium‐yl radical cation has a significantly shortened N−N bond and a nearly planar N2Si3 framework, in contrast to the starting material. According to DFT calculations, the shortened N−N bond has a total bond order of 1.5 with a π‐bond order of 0.5. The π bond can be regarded as a three‐π‐electron, two‐center bond. [ABSTRACT FROM AUTHOR]

The oxidation of silylated hydrazine, (Me3Si)2N−N(H)SiMe3, with silver salts led to the formation of a highly labile hydrazinium‐yl radical cation, [(Me3Si)2N−N(H)SiMe3].+, at very low temperatures (decomposition > −40 °C). EPR, NMR, DFT and Raman studies revealed the formation of a nitrogen‐centered radical cation along the N−N unit of the hydrazine. In the presence of the weakly coordinating anion [Al{OCH(CF3)2}4]−, crystallization and structural characterization in the solid state were achieved. The hydrazinium‐yl radical cation has a significantly shortened N−N bond and a nearly planar N2Si3 framework, in contrast to the starting material. According to DFT calculations, the shortened N−N bond has a total bond order of 1.5 with a π‐bond order of 0.5. The π bond can be regarded as a three‐π‐electron, two‐center bond. [ABSTRACT FROM AUTHOR]

Formal coordination of phosphorus(III) by a calix[4]pyrrole Schiff base ligand was achieved through the reaction of this ligand with PCl3 under basic conditions. The reaction product adopts a Pacman conformation with two P−Cl moieties, one in exo and one in endo position. It represents the first non‐metal compound of calix[4]pyrrole Schiff base ligands and of Pacman ligands in general. The spatial neighborhood of the two phosphorus atoms enables cooperative reactions. As a first example, the chloride abstraction with AgOTf is presented, yielding a macrocyclic dication with two embedded phosphorus(III) monocations, which both undergo a cooperative, internal activation reaction with an adjacent C=N double bond. This intramolecular redox process affords two pentacoordinated phosphorus(V) centers within the Pacman dication. All reaction products were fully characterized and all results are supported by computations. [ABSTRACT FROM AUTHOR]

A metal‐free, photoinduced aerobic tandem amine dehydrogenation/Povarov cyclization/aromatization reaction between N‐aryl glycine esters and indoles leads to tetracyclic 11H‐indolo[3,2‐c]quinolines under mild conditions and with high yields. The reaction can be performed by using molecular iodine along with visible light, or by combining an organic photoredox catalyst with a halide anion. Mechanistic studies reveal that product formation occurs through a combination of radical‐mediated oxidation steps with an iminium ion or N‐haloiminium ion [4+2]‐cycloaddition, and the N‐heterocyclic products constitute new analogues of the antiplasmodial natural alkaloid isocryptolepine. [ABSTRACT FROM AUTHOR]

The reactivity of the four‐membered NP3 ring system [RN(μ‐PCl)2PR] (R=Mes*=2,4,6‐tri‐tert‐butylphenyl) towards Lewis acids, Lewis bases, and reducing agents was investigated. Comparisons with the literature‐known, analogous cyclic compounds [ClP(μ‐NR)]2 (R=Ter=2,6‐dimesitylphenyl) and [ClP(μ‐PR)]2 (R=Mes*) are drawn, to obtain a better systematic understanding of the reactivity of cyclic NP species. Apart from experimental results, DFT computations are discussed to further the insight into bonding and electronic structure of these compounds. [ABSTRACT FROM AUTHOR]

A dichloro-cycloazatriphosphane that incorporates a cyclic NP3 backbone could be synthesized using knowledge gained from the chemistry of N2P2 and P4 ring systems. It fills the gap between the congeneric compounds [ClP(μ-NR)]2 and [ClP(μ-PR)]2 (R=sterically demanding substituent), and thus contributes to the systematic development of nitrogen-phosphorus chemistry in general. The title compound was studied with respect to its formation via a labile aminodiphosphene, which readily underwent different rearrangement reactions depending on the solvent. All compounds were fully characterized by experimental and computational methods. [ABSTRACT FROM AUTHOR]

The chemistry of arsenic cyanides has been investigated and is found to be completely different to the chemistry of the heavier analogs antimony and bismuth as well as phosphorus. The reaction of As(CN)3 with cyanide salts resulted in the formation of an unknown cyanido arsazolide heterocycle, which represents a structure isomer of the desired [As(CN)4]−. The structure, bonding, and formation of this unusual heterocycle is discussed featuring an arsenic mediated C−C coupling of cyanides. [AsC4N4]− salts with different counterions such as [PPh4]+, [PPN]+=[Ph3P- N-PPh3]+, Ag+, and [BMIm]+ are reported with [BMIm][AsC4N4] being a low-temperature ionic liquid ( Tm=−62 °C). [ABSTRACT FROM AUTHOR]

The heavy pnictogen tricyanides, E(CN)3 (E=Sb, Bi), were synthesized from EF3 and Me3SiCN in ionic liquids, for example, 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIm][OTf]), which prevents the oligomerization of the molecular E(CN)3 species by formation of [BMIm][E(CN)3(OTf)] salts in solution. Recrystallization of [BMIm][E(CN)3(OTf)] from THF led to the isolation and full characterization of the molecular species E(CN)3 ⋅2 THF. [ABSTRACT FROM AUTHOR]

Various new P-based ring systems were synthesised by transferring established reaction routes from NP chemistry to the analogous PP compounds. Due to the different electronic situations of phosphorus and nitrogen with respect to s and p character of the lone pair, different reactivity of the phosphorus compounds was observed, especially with regard to the specificity of the reactions and the stability of the products. Whereas Mes*NPCl (Mes*=2,4,6-tri- tert-butylphenyl) is stable in the solid state and in solution, the formal phosphorus congener Mes*PPCl is highly reactive and could not be observed. Instead, several formal dimers and trimers of Mes*PPCl could be isolated, which constitute an intriguing variety of three- and four-membered ring systems. [ABSTRACT FROM AUTHOR]

This work describes the synthesis and full characterization of a series of GaCl3 and B(C6F5)3 adducts of diazenes R1NNR2 (R1=R2=Me3Si, Ph; R1=Me3Si, R2=Ph). Trans-PhNNPh forms a stable adduct with GaCl3, whereas no adduct, but instead a frustrated Lewis acid-base pair is formed with B(C6F5)3. The cis-PhNNPh ⋅B(C6F5)3 adduct could only be isolated when UV light was used, which triggers the isomerization from trans- to cis-PhNNPh, which provides more space for the bulky borane. Treatment of trans-PhNNSiMe3 with GaCl3 led to the expected trans-PhNNSiMe3 ⋅GaCl3 adduct but the reaction with B(C6F5)3 triggered a 1,2-Me3Si shift, which resulted in the formation of a highly labile iso-diazene, Me3Si(Ph)NN; stabilized as a B(C6F5)3 adduct. Trans-Me3SiNNSiMe3 forms a labile cis-Me3SiNNSiMe3 ⋅B(C6F5)3 adduct, which isomerizes to give the transient iso-diazene species (Me3Si)2NN ⋅B(C6F5)3 upon heating. Both iso-diazene species insert easily into one BC bond of B(C6F5)3 to afford hydrazinoboranes. All new compounds were fully characterized by means of X-ray crystallography, vibrational spectroscopy, CHN analysis, and NMR spectroscopy. All compounds were further investigated by DFT and the bonding situation was assessed by natural bond orbital (NBO) analysis. [ABSTRACT FROM AUTHOR]

A series of heterodinuclear complexes with acetylene dithiolate (acdt2−) as the bridging moiety were synthesised by a facile one-pot procedure that avoided use of the highly elusive acetylene dithiol. Generation of the W-Ru complex [Tp′W(CN)(CO)(C2S2)Ru(η5-C5H5)(PPh3)] (Tp'=hydrotris(3,5-dimethylpyrazolyl)borate) and the W-Pd complexes [Tp′W(CN)(CO)(C2S2)Pd(dppe)] and [Tp′W(CO)2(C2S2)Pd(dppe)][PF6] (dppe=1,2-bis(diphenylphoshino)ethane), which exhibit a [W(η2-κ2-C2S2)M] core (M=Ru, Pd), was accomplished by using a transition-metal-assisted solvolytical removal of the Me3Si-ethyl thiol protecting groups. All intermediate species of the reaction have been fully characterised. The highly coloured W-Ru complex [Tp′W(CN)(CO)(C2S2)Ru(η5-C5H5)(PPh3)] shows reversible redox chemistry, as does the prototype complex [Tp′W(CO)2(C2S2)Ru(η5-C5H5)(PPh3)][PF6]. Single crystal X-ray diffraction and IR, EPR and UV/Vis spectroscopic studies in conjunction with DFT calculations prove the high electronic delocalisation of states over the acdt2− linker. Comparative studies revealed a higher donor strength and more pronounced dithiolate character of acdt2− in [Tp′W(CN)(CO)(C2S2)Ru(η5-C5H5)(PPh3)] relative to [Tp′W(CO)2(C2S2)Ru(η5-C5H5)(PPh3)]+. In addition, the influence of the overall complex charge on the metric parameters was investigated by single-crystal X-ray diffraction studies with the W-Pd complexes [Tp′WL2(C2S2)Pd(dppe)] (L=(CN−)(CO) or (CO)2). The central [W(C2S2)Pd] units exhibit high structural similarity, which indicates the extensive delocalisation of charge over both metals. [ABSTRACT FROM AUTHOR]