Reviews ChemistryOpen doi.org/10.1002/open.202000252 1 2 3 Pseudohalogen Chemistry in Ionic Liquids with Non- 4 5 innocent Cations and Anions 6 [a] [a] [a] [a] [a] 7 Sören Arlt, Kevin Bläsing, Jörg Harloff, Karoline Charlotte Laatz, Dirk Michalik, [c] [a, b] [a] [a] [a] 8 Simon Nier, Axel Schulz, Philip Stoer, Alrik Stoffers, and Alexander Villinger 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 ChemistryOpen 2020, 9, 1–11 1 © 2020 The Authors. Published by Wiley-VCH GmbH These are not the final page numbers! �� Wiley VCH Dienstag, 08.12.2020 2099 / 182250 [S. 1/11] 1 Reviews ChemistryOpen doi.org/10.1002/open.202000252 1 Within the second funding period of the SPP 1708 “Material [PPN][X(HCN)3] (X=N3, OCN) and [PPN][SCN(HCN)2] were ob- 2 Synthesis near Room Temperature”,which started in 2017, we tained when the crystallization was carried out at low temper- 3 were able to synthesize novel anionic species utilizing Ionic atures. Interestingly, reaction of [PPN]OCP with HCN was 4 À Liquids (ILs) both, as reaction media and reactant. ILs, bearing noticed, which led to the formation of [P(CN)2] , crystallizing as 5 the decomposable and non-innocent methyl carbonate anion HCN disolvate [PPN][P(CN·HCN)2]. Furthermore, we were able to 6 À [CO3Me] , served as starting material and enabled facile access isolate the novel cyanido(halido) silicate dianions of the type 7 2À 2À to pseudohalide salts by reaction with Me3SiÀ X (X=CN, N3, [SiCl0.78(CN)5.22] and [SiF(CN)5] and the hexa-substituted [Si 8 2À OCN, SCN). Starting with the synthesized Room temperature (CN)6] by temperature controlled halide/cyanide exchange 9 Ionic Liquid (RT-IL) [nBu3MeN][B(OMe)3(CN)], we were able to reactions. By facile neutralization reactions with the non- 10 crystallize the double salt [nBu3MeN]2[B(OMe)3(CN)](CN). Fur- innocent cation of [Et3HN]2[Si(CN)6] with MOH (M=Li, K), Li2[Si 11 thermore, we studied the reaction of [WCC]SCN and [WCC]CN (CN)6]·2 H2O and K2[Si(CN)6] were obtained, which form three 12 (WCC=weakly coordinating cation) with their corresponding dimensional coordination polymers. From salt metathesis 13 protic acids HX (X=SCN, CN), which resulted in formation of [H processes of M2[Si(CN)6] with different imidazolium bromides, 14 À À (NCS)2] and the temperature labile solvate anions [CN(HCN)n] we were able to isolate new imidazolium salts and the ionic 15 (n=2, 3). In addition, the highly labile anionic HCN solvates liquid [BMIm]2[Si(CN)6]. When reacting [Mes(nBu)Im]2[Si(CN)6] 16 were obtained from [PPN]X ([PPN]=μ-nitridobis(triphenylphos- with an excess of the strong Lewis acid B(C6F5)3, the voluminous 17 2À phonium), X= N3, OCN, SCN and OCP) and HCN. Crystals of adduct anion {Si[CN·B(C6F5)3]6} was obtained. 18 19 1. Introduction ionic liquids as precursors for inorganic materials,[81–83] ionic-liquid- 20 modified hybrid materials,[84–87] as well as the low-temperature 21 With this Minireview, we would like to summarize our results synthesis of thermoelectric materials[88–92] were investigated. More- 22 obtained during the 2nd period of the SPP 1708 “Material over, theoretical[93–106] and solubility[107–114] aspects during the 23 Synthesis near Room Temperature”. SPP 1708 was mainly set up synthesis process were studied. Among the publications with 24 to identify and demonstrate the advantages (but also the respect to main group molecule chemistry, some highlights are 25 disadvantages) of ILs when used as reaction media for synthesis in the isolation and characterization of [P Se ]+ by Ruck et al.,[115] the 26 3 4 contrast to common inorganic and organic solvents. In synthesis, cluster anions of the type [M Sn Se ]10À (M=Mn, Zn, Cd) by 27 4 4 17 ILs can play an active role as template, e.g. for the precipitation of Dehnen et al.[72] and the isolation of elusive hydrogen bonded 28 nanoparticles,[1–4] or it is more or less inert providing a highly polar poly(hydrogen halide) halogenates [X(HY)]À (X=Br, I, ClO À ; Y=Cl, 29 4 reaction media composed of ions.[5] Even after six years of SPP Br, CN) by Hasenstab-Riedel and coworker.[116] 30 1708, utilization of ILs as reaction media for the synthesis of Following our interests in pseudohalide chemistry, we 31 inorganic compounds is still a fairly new area steadily growing and focused on the synthesis of small molecules with the primary 32 with the focus on metal/metal oxide/metal nitride/metal halide goal to make very simple isolable compounds. During the first 33 (nano)particles of different types,[6–10] semiconductors,[11] and funding period we were able to synthesize and characterize 34 inorganic solids (e.g. zeolites).[12–24] Besides application in classic salts bearing new heteroleptic cyanido(fluorido)phosphate 35 solid state chemistry, ILs can be used as reaction media to prepare anions of the general formula [PF (CN) ]À (n=1À 4),[117,118] as 36 6À n n (oligomeric) metal complexes, metal organic frameworks, coordi- well as the homoleptic tetracyanidoborate anion [B(CN) ]À ,[119] 37 4 nation polymers[25–35] or cluster compounds incorporating main by very mild Lewis-acid catalyzed synthesis protocols, when 38 group elements.[36–41] Within SPP 1708, the synthesis of intermetal- starting from ILs. We succeeded in the synthesis and structural 39 lic cluster and nanoparticles,[3,42–56] the controlled synthesis of characterization of molecular pnictogen tricyanides E(CN) (E= 40 3 polyanions and cations,[57–61] solvent-free chalcogenidometal-con- Sb, Bi), which were stabilized in the IL [BMIm][OTf] ([BMIm]=1- 41 taining materials,[62–75] deposition of nanocrystalline materials,[76–80] nButyl-3-methylimidazolium, [OTf]=F CSO OÀ ), thus preventing 42 3 2 these species from oligomerization.[120] Utilizing ILs, we were 43 2À [a] Dr. S. Arlt, Dr. K. Bläsing, Dr. J. Harloff, K. C. Laatz, Dr. D. Michalik, able to synthesize salts with homoleptic [E(CN) ] anions (E= 44 5 Prof. A. Schulz, P. Stoer, Dr. A. Stoffers, Dr. A. Villinger Sb, Bi), but never formed any higher substituted species like [Bi 45 Anorganische Chemie, Institut fur Chemie, Universität Rostock 3À 5À A.-Einstein-Str. 3a 18059 Rostock (Germany) (CN)6] or [Bi2(CN)11] , which we obtained when using 46 [121] E-mail: [email protected] common organic solvents such as acetonitrile. Our attempts 47 [b] Prof. A. Schulz in synthesizing cyanidoarsenates of the type [As(CN) ]nÀ (n= 48 3 +n Materialdesign, Leibniz-Institut für Katalyse an der Universität Rostock À À A.-Einstein-Str. 29a 1 3) always led to formation of an isomer of [As(CN)4] , the 49 À 18059 Rostock (Germany) arsazolide heterocycle [AsC N ] , regardless of whether we used 50 4 4 [c] S. Nier ILs or organic solvents like acetonitrile.[122] 51 Anorganische Chemie, Institut für Chemie, Philipps-Universität Marburg Here, we mainly want to summarize on novel pseudohalide- 52 Hans-Meerwein-Straße 4 containing anions that were obtained using ILs as reaction 53 35032 Marburg (Germany) E-mail: [email protected] media. 54 © 2020 The Authors. Published by Wiley-VCH GmbH. This is an open access 55 article under the terms of the Creative Commons Attribution License, which 56 permits use, distribution and reproduction in any medium, provided the original work is properly cited. 57 ChemistryOpen 2020, 9, 1–11 www.chemistryopen.org 2 © 2020 The Authors. Published by Wiley-VCH GmbH These are not the final page numbers! �� Wiley VCH Dienstag, 08.12.2020 2099 / 182250 [S. 2/11] 1 Reviews ChemistryOpen doi.org/10.1002/open.202000252 2. Synthesis of Pure Pseudohalide Containing which the latter was synthesized as the [Ph P]+ salt by exposure 1 4 [123–125] of CO to a concentrated solution of [Ph P]CN in acetonitrile. 2 ILs from ILs with Decomposable Anions 2 4 First, we tried to isolate pseudohaloformate anions from 3 concentrated and cooled reaction solutions of [R MeN][CO Me] 4 3 3 We started this project with the synthesis of various and Me SiÀ X in acetonitrile.[133] But even at À 40 °C the release 5 3 trialkylmethylammonium- ([R MeN]: R=Et, nPr, nBu)[123,124] and of gaseous CO was observed and no new signals for any 6 3 2 methyltriphenylphosphonium methylcarbonates.[125] They were [CO X]À species could be observed by means of 13C{1H} NMR 7 2 formed in autoclave reactions at autogenous pressure spectroscopy. Subsequently, a solvent free process was used, 8 (Scheme 1), due to a modified reaction, which was first from which the [CO CN]À anion was synthesized with [Et MeN]+ 9 2 3 described by Werntz[126] and taken up again in later years by as counter cation, when heating pure [Et MeN]CN to 150 °C in a 10 3 various working groups.[127–129] CO atmosphere at a pressure of 3 bar. Initially, the salt 11 2 In a subsequent reaction we synthesized the pseudohalides remained solid at high temperature but then liquefied when it 12 of the type [R MeN]X (R=Et, nBu: X=CN, N , OCN, SCN;[123] R= was cooled down to room temperature.