A 2D Polychloride Network Held Together by Halogen–Halogen Interactions

Iodine-Rich Supramolecular Complexes of Chlorobismuthates(III): Unusual Lone Pair Activity and Features of Halogen Bonding in Crystals

The first chrorobismuthate(III) supramolecular hybrids with halogen-bond-linked I2, (Py(CH2)2Py){[BiCl5](I2)} (1) and (Py(CH2)3Py){[BiCl5](I2)0.5} (2), were synthesized via the reaction between Bi2O3, I2, and salts of the corresponding cations in HCl. The compounds featured one- and two-dimensional (2D) supramolecular motifs built by I···Cl contacts; in the case of 1, Bi(III) is pentacoordinated due to the lone pair activity, which also interacted with I2 pi-orbitals, as confirmed by density functional theory (DFT) calculations. Both complexes exhibited moderate thermal stabilities and relatively narrow optical band gaps.

Oxychloridoselenites(IV) with cubane-derived anions and stepwise chlorine-to-oxygen exchange

The novel oxychloridoselenites(IV) [BMIm][Se₃Cl₁₃] (1), [BMIm][Se₄Cl₁₅O] (2), [BMIm]₂[Se₄Cl₁₄O₂] (3), [BMPyr]₂[Se₄Cl₁₄O₂] (4), [BMPyr]₂[Se₆Cl₁₈O₄] (5), [BMIm]₂[SeCl₄O] (6), [BMPyr]₂[Se₂Cl₆O₂] (7), and [BMPyr]₂[Se₆Cl₁₄O₆] (8) are prepared by ionic-liquid-based synthesis. Accordingly, SeCl₄, SeO₂ (1-6), and/or SeOCl₂ (7,8) as the starting materials are reacted in [BMIm]Cl or [BMPyr]Cl as ionic liquid (BMIm: 1-butyl-3-methylimidazolium, BMPyr: 1-butyl-1-methylpyrrolidinium; partially with AlCl₃ in addition). Generally, the composition and structure of title compounds can be derived from the tetrameric, heterocubane-type (SeCl₄)₄ as the initial building unit. Thus, chlorine is successively exchanged by oxygen from 1 to 8. Moreover, the four edge-sharing (SeCl₆) octahedra in (SeCl₄)₄ are increasingly dismantled, ending with a [SeCl₄O]^2- anion as a single pseudo-octahedron in 6. Based on the weakly coordinating ionic liquid, it is possible to selectively obtain the different species via synthesis near room temperature (20-80 °C). The oxychloridoselenite anions [Se₄Cl₁₅O]^-, [Se₄Cl₁₄O₂]^2-, [Se₆Cl₁₈O₄]^2-, and [Se₆Cl₁₄O₆]^2- are obtained for the first time. The title compounds are characterized by X-ray structure analysis based on single crystals and powders as well as by infrared spectroscopy and thermal analysis.

Reactions of noble-metal oxides in ionic liquids near room temperature

The reaction of Ag₂O, Au₂O₃, and HgO with CuCl, CuI, AgCl, AgI, AuCl, and AuI in ionic liquids ([EMIm]Cl, [BMIm]Cl) near room temperature (20-80 °C) is evaluated and results in the new compounds (C₈H₁₄N₂)CuCl, (C₈H₁₄N₂)AgI, (C₆H₁₀N₂)AuCl, [(C₈H₁₄N₂)₂Hg][CuCl₃], [(C₈H₁₄N₂)₂Hg][AgCl₃], and [EMIm][Ag₂I₂Cl]. Thereof, (C₈H₁₄N₂)CuCl, (C₈H₁₄N₂)AgI, (C₆H₁₀N₂)AuCl, [(C₈H₁₄N₂)₂Hg][CuCl₃], and [(C₈H₁₄N₂)₂Hg][AgCl₃] are NHC complexes (NHC: N-heterocyclic carbene) with M-C bonds (M: Cu, Ag, Au, Hg). Whereas (C₈H₁₄N₂)CuCl and (C₈H₁₄N₂)AgI crystallize as single molecules, (C₆H₁₀N₂)AuCl is dimerized via aurophilic interactions. [(C₈H₁₄N₂)₂Hg][CuCl₃] and [(C₈H₁₄N₂)₂Hg][AgCl₃] exhibit Hg atoms with two Hg-C bonds. Moreover, (C₈H₁₄N₂)AgI shows intense green fluorescence at room temperature with a quantum yield of 44%, whereas all other compounds do not show any emission at room temperature. Finally, [EMIm][Ag₂I₂Cl] is not an NHC compound but contains _∞ ¹[AgI_1/2I_2/4Cl_1/2]^- chains with infinite d¹⁰-d¹⁰ interaction of the silver atoms. The title compounds are characterized by single-crystal structure analysis, infrared spectroscopy, thermogravimetry, and fluorescence spectroscopy.

Selenium(IV) Polybromide Complexes: Structural Diversity Driven by Halogen and Chalcogen Bonding

Reactions between bromoselenate(IV)-containing solutions, dibromine and salts of pyridinium-family organic cations resulted in structurally diverse, bromine-rich polybromine-bromoselenates(IV): (4-MePyH)₅[Se₂Br₉][SeBr₆](Br₃)₂ (1), (2-MePyH)₂{[SeBr₆](Br₂)} (2), (PyH)₂{[SeBr₅]Br(Br₂)₂} (3), (1-MePy)₂{[SeBr₆](Br₂)} (4). The compounds feature halogen and (in the case of 3) chalcogen bonding in solid state, resulting in formation of supramolecular architectures of different dimensionality. DFT calculations allowed estimation of the energies of non-covalent interactions in 1–4; additionally, characterization by Raman spectroscopy was performed.

Room-Temperature Synthesis of [BMIm][Sn5O2Cl7] with ∞1(Sn2OCl2) Strands in a Saline [BMIm][SnCl3] Matrix

The novel tin(II) oxychloride [BMIm][Sn5O2Cl7] (BMIm = 1-butyl-3-methylimidazolium) is obtained by the room-temperature reaction (25 °C) of black SnO and SnCl2 in [BMIm]Cl/SnCl2 as an ionic liquid. The title compound can be described as composed of noncharged, infinite ∞1(Sn2OCl2) strands that are embedded in a saline matrix of [BMIm]+ and [SnCl3]-. The ∞1(Sn2OCl2) strands consist of a backbone of edge-sharing OSn4/2 tetrahedra, which represent one-dimensional (1D) strands cut out of the layer-type structure of SnO. In [BMIm][Sn5O2Cl7], the ∞1(Sn2OCl2) strands, which mimic a 1D semiconductor, are terminated by chlorine atoms, whereas they are interconnected by oxygen atoms in the 2D semiconductor SnO. The view of the noncharged ∞1(Sn2OCl2) strands in a saline [BMIm][SnCl3] matrix is validated by dissolution experiments. Thus, electron microscopy and Raman spectroscopy show a deconstruction of [BMIm][Sn5O2Cl7] single crystals after treatment with chloroform with a dissolution of [BMIm][SnCl3], the formation of SnCl2 needles, and tin oxide as a solid remain.

Dichlorine-containing chlorobismuthate(iii) supramolecular hybrid: structure and experimental studies of stability

The chlorine-rich complex (Me4N)3{[Bi2Cl9](Cl2)} (1) features dichlorine units incorporated into a chlorometalate matrix via halogen bonding.

Oxochloroselenate(IV) with Incorporated {Cl2 }: The Case of Strong Cl⋅⋅⋅Cl Halogen Bonding

Reaction of SeO₂ , tetramethylammonium (TMA) chloride, aqueous HCl and Cl₂ yields oxochloroselenate with incorporated Cl₂ units, TMA₃ {[Se₂ O₂ Cl₇ ](Cl₂ )}. The main feature of this compound is the strong (up to 3.5 kcal mol^-1 , according to DFT calculations) Cl⋅⋅⋅Cl bonding, which is also detected by Raman spectroscopy.

Rule, Not Exclusion: Formation of Dichlorine-Containing Supramolecular Complexes with Chlorometalates(IV)

Supramolecular derivatives of chlorostannate(IV) and -plumbate(IV) with {Cl₂} units, Cat₂{[MCl₆](Cl₂)_x} (1-5; M = Sn, Pb, cat = 1-methylpyridinium (1-MePy), tetramethylammonium (TMA)) were prepared and characterized by X-ray diffractometry and Raman spectroscopy. In particular, the TMA-containing complexes demonstrate remarkable thermal stability, releasing Cl₂ only at elevated temperatures.

Conductivity and Redox Potentials of Ionic Liquid Trihalogen Monoanions [X3 ]- , [XY2 ]- , and [BrF4 ]- (X=Cl, Br, I and Y=Cl, Br)

The ionic liquid (IL) trihalogen monoanions [N2221 ][X3 ]- and [N2221 ][XY2 ]- ([N2221 ]+ =triethylmethylammonium, X=Cl, Br, I, Y=Cl, Br) were investigated electrochemically via temperature dependent conductance and cyclic voltammetry (CV) measurements. The polyhalogen monoanions were measured both as neat salts and as double salts in 1-butyl-1-methyl-pyrrolidinium trifluoromethane-sulfonate ([BMP][OTf], [X3 ]- /[XY2 ]- 0.5 M). Lighter IL trihalogen monoanions displayed higher conductivities than their heavier homologues, with [Cl3 ]- being 1.1 and 3.7 times greater than [Br3 ]- and [I3 ]- , respectively. The addition of [BMP][OTf] reduced the conductivity significantly. Within the group of polyhalogen monoanions, the oxidation potential develops in the series [Cl3 ]- >[BrCl2 ]- >[Br3 ]- >[IBr2 ]- >[ICl2 ]- >[I3 ]- . The redox potential of the interhalogen monoanions was found to be primarily determined by the central halogen, I in [ICl2 ]- and [IBr2 ]- , and Br in [BrCl2 ]- . Additionally, tetrafluorobromate(III) ([N2221 ]+ [BrF4 ]- ) was analyzed via CV in MeCN at 0 °C, yielding a single reversible redox process ([BrF2 ]- /[BrF4 ]- ).

Opening the Third Century of Polyhalide Chemistry: Thermally Stable Complex with "Trapped" Dichlorine

Unlike polyhalides of heavier halogens, polychlorides still remain exotic curiosities. Herein, we report preparation and investigation of complexes Cat₂ {[TeCl₆ ](Cl₂ )} (cat=1-methylpyridinium (1) and tetramethylammonium (2)) where dichlorine units are "trapped" by chlorotellurate(IV) anions via a system of non-covalent Cl⋅⋅⋅Cl interactions. Complex 2 reveals a record thermal stability (>100 °C) for inclusion compounds with Cl₂ , indications that such compounds can be used as solid Cl₂ source.

Quest for Compounds at the Verge of Charge Transfer Instabilities: The Case of Silver(II) Chloride †

Electron-transfer processes constitute one important limiting factor governing stability of solids. One classical case is that of CuI2, which has never been prepared at ambient pressure conditions due to feasibility of charge transfer between metal and nonmetal (CuI2 → CuI + ½ I2). Sometimes, redox instabilities involve two metal centers, e.g., AgO is not an oxide of divalent silver but rather silver(I) dioxoargentate(III), Ag(I)[Ag(III)O2]. Here, we look at the particularly interesting case of a hypothetical AgCl2 where both types of redox instabilities operate simultaneously. Since standard redox potential of the Ag(II)/Ag(I) redox pair reaches some 2 V versus Normal Hydrogen Electrode (NHE), it might be expected that Ag(II) would oxidize Cl− anion with great ease (standard redox potential of the ½ Cl2/Cl− pair is + 1.36 V versus Normal Hydrogen Electrode). However, ionic Ag(II)Cl2 benefits from long-distance electrostatic stabilization to a much larger degree than Ag(I)Cl + ½ Cl2, which affects relative stability. Moreover, Ag(II) may disproportionate in its chloride, just like it does in an oxide; this is what AuCl2 does, its formula corresponding in fact to Au(I)[Au(III)Cl4]. Formation of polychloride substructure, as for organic derivatives of Cl3− anion, is yet another possibility. All that creates a very complicated potential energy surface with a few chemically distinct minima i.e., diverse polymorphic forms present. Here, results of our theoretical study for AgCl2 will be presented including outcome of evolutionary algorithm structure prediction method, and the chemical identity of the most stable form will be uncovered together with its presumed magnetic properties. Contrary to previous rough estimates suggesting substantial instability of AgCl2, we find that AgCl2 is only slightly metastable (by 52 meV per formula unit) with respect to the known AgCl and ½ Cl2, stable with respect to elements, and simultaneously dynamically (i.e., phonon) stable. Thus, our results point out to conceivable existence of AgCl2 which should be targeted via non-equilibrium approaches.

The Binary Iodine-Chlorine Octahalide Series [In Cl8-n ]2- (n=3, 3.6, 4)

The octanuclear iodine-chlorine interhalides [I₄ Cl₄ ]^2- and [I₃ Cl₅ ]^2- were prepared in two steps. Firstly, addition of ICl to the triaminocyclopropenium chloride salt [C₃ (NEt₂ )₃ ]Cl forms the trihalide ICl₂ ^- salt, secondly, addition of half an equivalent of I₂ or ICl, respectively, gave the desired products upon crystallization at low temperature. The non-stoichiometric octahalide [I_3.6 Cl_4.4 ]^2- was obtained after heating a CH₂ Cl₂ solution of the ICl₂ ^- salt to reflux for 2 hours followed crystallization. [I₄ Cl₄ ]^2- is best described as two ICl₂ ^- anions bridged by I₂ , whereas [I₃ Cl₅ ]^2- is best described as an [I₂ Cl₃ ]^- pentahalide with a weak halogen bond to an ICl₂ ^- trihalide. The octahalides were characterized by X-ray crystallography, computational studies, Raman and Far-IR spectroscopies, as well as by TGA and melting point.

Synthesis and Characterization of [Br3 ][MF6 ] (M=Sb, Ir), as well as Quantum Chemical Study of [Br3 ]+ Structure, Chemical Bonding, and Relativistic Effects Compared with [XBr2 ]+ (X=Br, I, At, Ts) and [TsZ2 ]+ (Z=F, Cl, Br, I, At, Ts)

[Br₃ ][SbF₆ ] and [Br₃ ][IrF₆ ] were synthesized by interaction of BrF₃ with Sb₂ O₃ or iridium metal, respectively. The former compound crystallizes in the orthorhombic space group Pbcn (No. 60) with a=11.9269(7), b=11.5370(7), c=12.0640(6) Å, V=1660.01(16) ų , Z=8 at 100 K. The latter compound crystallizes in the triclinic space group P 1 ‾ (No. 2) with a=5.4686(5), b=7.6861(8), c=9.9830(9) Å, α=85.320(8), β=82.060(7), γ=78.466(7)°, V=406.56(7) ų , Z=2 at 100 K. Both compounds contain the cation [Br₃ ]⁺ , which has a bent structure and is coordinated by octahedron-like anions [MF₆ ]^- (M=Sb, Ir). Experimentally obtained cell parameters, bond lengths, and angles are confirmed by solid-state DFT calculations, which differ from the experimental values by less than 2 %. Relativistic effects on the structure of the tribromonium(1+) cation are studied computationally and found to be small. For the heaviest analogues containing At and Ts, however, pronounced relativistic effects are found, which lead to a linear structure of the polyhalogen cation.

Oriented External Electric Fields: Tweezers and Catalysts for Reactivity in Halogen-Bond Complexes

This theoretical study establishes ways of controlling and enabling an uncommon chemical reaction, the displacement reaction, B:---(X-Y) → (B-X)⁺ + :Y^-, which is nascent from a B:---(X-Y) halogen bond (XB) by nucleophilic attack of the base, B:, on the halogen, X. In most of the 14 cases examined, these reactions possess high barriers either in the gas phase (where the X-Y bond dissociates to radicals) or in solvents such as CH₂Cl₂ and CH₃CN (which lead to endothermic processes). Thus, generally, the XB species are trapped in deep minima, and their reactions are not allowed without catalysis. However, when an oriented-external electric field (OEEF) is directed along the B---X---Y reaction axis, the field acts as electric tweezers that orient the XB along the field's axis, and intensely catalyze the process, by tens of kcal/mol, thus rendering the reaction allowed. Flipping the OEEF along the reaction axis inhibits the reaction and weakens the interaction of the XB. Furthermore, at a critical OEEF, each XB undergoes spontaneous and barrier-free reaction. As such, OEEF achieves quite tight control of the structure and reactivity of XB species. Valence bond modeling is used to elucidate the means whereby OEEFs exert their control.

Ionic liquids with polychloride anions as effective oxidants for the dissolution of UO2

Polychloride ionic liquids can not only successfully dissolve UO₂, but also raise the chlorine efficiency.

A Novel Family of Polyiodo-Bromoantimonate(III) Complexes: Cation-Driven Self-Assembly of Photoconductive Metal-Polyhalide Frameworks

In the presence of different cations, reactions of [SbBr₆ ]^3- and I₂ result in a new family of diverse supramolecular 1D polyiodide-bromoantimonate networks. The coordination number of Sb, as well as geometry of assembling {I_x }^n- polyhalide units, can vary, resulting in unprecedented structural types. The nature of I⋅⋅⋅Br interactions was studied by DFT calculations; estimated energy values are 1.6-6.9 kcal mol^-1 . Some of the compounds showed strong photoconductivity in thin films, suggesting multiple feasible applications in optoelectronics and solar energy conversion.

Bromo- and Polybromoantimonates(V): Structural and Theoretical Studies of Hybrid Halogen-Rich Halometalate Frameworks

Cation-dependent reactions "[SbBr₆ ]^3- +Br₂ +HBr+CationBr_x " result in the formation of bromide/polybromide complexes with zero-, one-, two-, or three-dimensional supramolecular frameworks and different Br/Sb ratios (up to 11). Seven new compounds representing six structural types were characterized by XRD and thermogravimetric analysis and DFT calculations enabled estimation of the energies of the Br⋅⋅⋅Br contacts (1.1-4.6 kcal mol^-1 ).

Synthesis and Characterization of Nonclassical Interhalides Based on Bromine Monochloride

Due to a more distinct σ-hole, BrCl is able to form stronger halogen bonds than those in polyhalogen anions based on Cl₂ and Br₂ . This stabilization allows the crystallographic characterization of a variety of new polyinterhalides, in which chloride functions as the central ion as shown by the molecular structures of [AsPh₄ ][Cl(BrCl)₃ ] and [CCl(NMe₂ )₂ ][Cl(BrCl)₅ ]. Furthermore, the solid-state structure of an octahedrally coordinated nonclassical interhalide is reported for the first time. The tridecainterhalide monoanion [Cl(BrCl)₆ ]^- consists of a central chloride ion, which is coordinated by six BrCl molecules in a slightly distorted octahedral structure. All new compounds were characterized by single-crystal X-ray diffraction (XRD), NMR and Raman spectroscopy, as well as quantum-chemical calculations.

Bromine-rich complexes of bismuth: experimental and theoretical studies

Three novel polybromide complexes of bismuth(iii) – (2,6-MePyH)₃[BiBr₅(Br₃)] (1), (H₂bpp){[BiBr₅](Br₂)} (2) and (3-ClPyH)₂{[BiBr₅](Br₂)} (3) – were synthesized.

One-dimensional polymeric polybromotellurates(iv): structural and theoretical insights into halogen⋯halogen contacts

Reactions of TeO₂and Br₂in concentrated HBr in the presence of various organic cations resulted in the formation of one-dimensional supramolecular polymers with the structure cation₂{[TeBr₆](Br₂)}.

Matrix-isolation and comparative far-IR investigation of free linear [Cl3]−and a series of alkali trichlorides

Here we discuss the reaction products of laser ablated alkali chlorides and elemental chlorine.

Structural Proof for the First Dianion of a Polychloride: Investigation of [Cl8 ](2.)

The polychloride salt [CCl(NMe2 )2 ](+) 2 [Cl8 ](2-) was synthesized and crystallized in the ionic liquid [BMP]OTf. The compound was fully characterized by Raman spectroscopy as well as X-ray single-crystal structure determination, and represents the first example of a polychloride dianion to be described. Detailed gas-phase and solid-state calculations concerning the nature of the bonding situation were also performed.