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- ItemAzadiphosphaindane-1,3-diyls: A Class of Resonance-Stabilized Biradicals(Weinheim : Wiley-VCH, 2021) Bresien, Jonas; Michalik, Dirk; Schulz, Axel; Villinger, Alexander; Zander, EdgarConversion 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 GmbH
- ItemPseudohalogen Chemistry in Ionic Liquids with Non-innocent Cations and Anions(Weinheim : Wiley-VCH-Verl., 2020) Arlt, Sören; Bläsing, Kevin; Harloff, Jörg; Laatz, Karoline Charlotte; Michalik, Dirk; Nier, Simon; Schulz, Axel; Stoer, Philip; Stoffers, Alrik; Villinger, AlexanderWithin the second funding period of the SPP 1708 “Material Synthesis near Room Temperature”,which started in 2017, we were able to synthesize novel anionic species utilizing Ionic Liquids (ILs) both, as reaction media and reactant. ILs, bearing the decomposable and non-innocent methyl carbonate anion [CO3Me]−, served as starting material and enabled facile access to pseudohalide salts by reaction with Me3Si−X (X=CN, N3, OCN, SCN). Starting with the synthesized Room temperature Ionic Liquid (RT-IL) [nBu3MeN][B(OMe)3(CN)], we were able to crystallize the double salt [nBu3MeN]2[B(OMe)3(CN)](CN). Furthermore, we studied the reaction of [WCC]SCN and [WCC]CN (WCC=weakly coordinating cation) with their corresponding protic acids HX (X=SCN, CN), which resulted in formation of [H(NCS)2]− and the temperature labile solvate anions [CN(HCN)n]− (n=2, 3). In addition, the highly labile anionic HCN solvates were obtained from [PPN]X ([PPN]=μ-nitridobis(triphenylphosphonium), X=N3, OCN, SCN and OCP) and HCN. Crystals of [PPN][X(HCN)3] (X=N3, OCN) and [PPN][SCN(HCN)2] were obtained when the crystallization was carried out at low temperatures. Interestingly, reaction of [PPN]OCP with HCN was noticed, which led to the formation of [P(CN)2]−, crystallizing as HCN disolvate [PPN][P(CN⋅HCN)2]. Furthermore, we were able to isolate the novel cyanido(halido) silicate dianions of the type [SiCl0.78(CN)5.22]2− and [SiF(CN)5]2− and the hexa-substituted [Si(CN)6]2− by temperature controlled halide/cyanide exchange reactions. By facile neutralization reactions with the non-innocent cation of [Et3HN]2[Si(CN)6] with MOH (M=Li, K), Li2[Si(CN)6] ⋅ 2 H2O and K2[Si(CN)6] were obtained, which form three dimensional coordination polymers. From salt metathesis processes of M2[Si(CN)6] with different imidazolium bromides, we were able to isolate new imidazolium salts and the ionic liquid [BMIm]2[Si(CN)6]. When reacting [Mes(nBu)Im]2[Si(CN)6] with an excess of the strong Lewis acid B(C6F5)3, the voluminous adduct anion {Si[CN⋅B(C6F5)3]6}2− was obtained. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemLow temperature isolation of a dinuclear silver complex of the cyclotetraphosphane [ClP(μ-PMes*)]2(London : Soc., 2015) Bresien, Jonas; Schulz, Axel; Villinger, AlexanderThe 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.
- ItemCorrection: Increasing steric demand through flexible bulk – primary phosphanes with 2,6-bis(benzhydryl)phenyl backbones(London : Soc., 2019) Bresien, Jonas; Goicoechea, Jose M.; Hinz, Alexander; Scharnhölz, Moritz T.; Schulz, Axel; Suhrbier, Tim; Villinger, AlexanderCorrection for 'Increasing steric demand through flexible bulk-primary phosphanes with 2,6-bis(benzhydryl)phenyl backbones' by Jonas Bresien et al., Dalton Trans., 2019, 48, 3786-3794. © 2019 The Royal Society of Chemistry.
- ItemSynthetic strategies to bicyclic tetraphosphanes using P1, P2 and P4 building blocks(London : Soc., 2015) Bresien, Jonas; Faust, Kirill; Hering-Junghans, Christian; Rothe, Julia; Schulz, Axel; Villinger, AlexanderDifferent 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.
- ItemReduction of dichloro(diaza-phospha)stibanes – isolation of a donor-stabilized distibenium dication(London : Soc., 2016) Hinz, Alexander; Rothe, Julia; Schulz, Axel; Villinger, AlexanderA 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.
- ItemHighly selective visible light-induced Ti–O bond splitting in an ansa-titanocene dihydroxido complex(Cambridge : Soc., 2015) Godemann, Christian; Dura, Laura; Hollmann, Dirk; Grabow, Kathleen; Bentrup, Ursula; Jiao, Haijun; Schulz, Axel; Brückner, Angelika; Beweries, TorstenIrradiation of a substituted ansa-titanocene(IV) dihydroxido complex with visible light induces Ti–O bond dissociation. In contrast to previous studies on structurally similar unbridged complexes, no side reactions are observed and formation of the Ti(III) species is highly selective. The formation of OH radicals was proved using a biradicaloid species.
- ItemA Systematic Survey of the Reactivity of Chlorinated N2P2, NP3 and P4 Ring Systems(Weinheim : Wiley-VCH, 2019) Bresien, Jonas; Eickhoff, Liesa; Schulz, Axel; Suhrbier, Tim; Villinger, AlexanderThe 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. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemAccessing heavy allyl-analogous [(TerN)2E]− (E = Sb, Bi) ions and their reactivity towards ECl3(Cambridge : Soc., 2015) Hinz, Alexander; Schulz, Axel; Villinger, AlexanderThe 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].
- ItemA chemical reaction controlled by light-activated molecular switches based on heterocyclopentanediyls(Cambridge : RSC, 2019) Bresien, Jonas; Kröger-Badge, Thomas; Lochbrunner, Stefan; Michalik, Dirk; Müller, Henrik; Schulz, Axel; Zander, EdgarMolecular switches are molecules that can reversibly be shifted between at least two stable states with different physical and chemical properties, making them interesting for application as chemical sensors or molecular machines. We recently discovered that five-membered, cyclic biradicals based on group 15 elements are efficient and robust photochemical switches that can be activated by red light. The quantum yield of the photo-isomerization is as high as 24.6%, and the thermal equilibration of the photo-activation product proceeds rapidly at ambient temperature. The fully reversible process was studied by experimental and high-level ab initio techniques. We could further demonstrate that the biradical character could be completely turned on and off, so the system could be applied to control chemical equilibria that involve activation products of the cyclic biradicals. © 2019 The Royal Society of Chemistry.