Two polymorph modifications of tris(hexafluoroacetylacetonato)iron(III) revealed: is that common for other trivalent metals?

A long-standing issue about the correct identification of an important starting reagent, iron(III) hexafluoroacetylacetonate, Fe(hfac)3 (1), has been resolved. The tris-chelated mononuclear complex was found to crystallize in two polymorph modifications which can be assigned as the low-temperature (1-L) monoclinic P21/n and the high-temperature (1-H) trigonal P\overline{3}. Low-temperature polymorph 1-L was found to transform to 1-H upon sublimation at 44 °C. Two modifications are clearly distinguished by powder X-ray diffraction (PXRD), single-crystal X-ray diffraction, differential scanning calorimetry (DSC), and melting-point measurements. On the other hand, the two forms share similar characteristics in direct analysis in real-time mass spectrometry (DART-MS), attenuated total reflection (ATR) spectroscopy, and some physical properties, such as color, volatility, sensitivity, and solubility. Analysis of the literature and some of our preliminary data strongly suggest that the appearance of two polymorph modifications for trivalent metal (both transition and main group) hexafluoroacetylacetonates is a common case for several largely used complexes not yet accounted for in the crystallographic databases.

From cubane-assembled Mn-oxo clusters to monodispersed manganese oxide colloidal nanocrystals.

The assemblies of [M4O4] (M = metal) cubanes represent a fascinating class of materials for a variety of application fields. Although such a structural characteristic is relatively common in small molecules and in extended bulk solids, high nuclearity clusters composed of multiple [M4O4] units as their backbones are rare. In this work, we report two new Mn-oxo clusters, MnII 8MnIII 10O10(OOCMe)12(OMe)14(py)2 ([Mn18-Ac]) and MnII 4MnIII 14O14(OOCCMe3)8(OMe)14(MeOH)5(py) ([Mn18-Piv]), whose core structures are assemblies of either 6- or 7-cubanes in different packing patterns, which have been unambiguously revealed by single crystal X-ray diffraction technique. The cubane-assembled structural features can be deemed as the embryonic structures of the bulk manganese oxide. Herein, this report demonstrates the first case study of utilizing Mn-oxo clusters as precursors for the preparation of manganese oxide nanocrystals, which has never been explored before. Through a simple colloidal synthetic approach, high-quality, monodisperse Mn3O4 nanocrystals can be readily prepared by employing both precursors, while their morphologies were found to be quite different. This work confirms that the structural similarity between precursors and nanomaterials is instrumental in affording more kinetically efficient pathways for materials formation, and the structure of the precursor has a significant impact on the morphology of final nanocrystal products.

Trickier than It Looks: Isomerization between Five- and Six-Coordinated Zinc in Heterometallic Li2Zn2 Molecule.

This report describes the synthesis and characterization of two heterobimetallic Li-Zn coordination isomers [Li2Zn2(tbaoac)6] (tbaoac = tert-butyl acetoacetato) that have been isolated separately by the same stoichiometric reaction run in different organic solvents. The 6-coordinated zinc isomer (6-Zn) was synthesized in acetone with high yield, while the 5-coordinated one (5-Zn) was readily obtained from ethanol. The 5-Zn isomer has a low solubility in organic solvents such as alkanes and haloalkanes, while its 6-Zn counterpart exhibits a good solubility in almost all common solvents. Two isomeric molecules feature similar centrosymmetric tetranuclear cyclic assemblies, which are different in their arrangement of tbaoac ligands. While all ligands act as µ2-type in the structure of 5-Zn, the two tbaoac groups chelating Li appear as µ3-type in 6-Zn, thus providing an additional coordination for Zn ions. However, the real structural transformation between these isomers was shown to be more complex than simply making or breaking a couple of Zn-O bonds. X-ray single-crystal structure analysis, powder X-ray diffraction, multinuclear NMR, DART mass spectrometry, ICP-OES analysis, and TGA have been employed for the characterization of the isomers. The combination of powder X-ray diffraction and 1H NMR investigation revealed that 6-Zn isomer can be quantitatively transformed to 5-Zn in ethanol, while the reverse conversion instantly takes place in acetone.

Synthesis, Structure, and Characterizations of a Volatile/Soluble Heterometallic Hexanuclear Precursor [NaMn2(thd)4(OAc)]2.

The paper describes a heterobimetallic mixed-ligand hexanuclear precursor [NaMn2(thd)4(OAc)]2 (1) (thd = 2,2,6,6-tetramethyl-3,5-heptadionate; OAc = acetate) that was designed based on its lithium homoleptic analogue, [LiMn2(thd)5], by replacing one of the thd ligands with an acetate group in order to accommodate 5-coordinated sodium instead of tetrahedral lithium ion. The complex, which is highly volatile and soluble in a variety of common solvents, has been synthesized by both the solid-state and solution methods. The unique "dimer-of-trimers" heterometallic structure consists of two trinuclear [NaMnII2(thd)4]+ units firmly bridged by two acetate ligands. X-ray diffraction techniques, DART mass spectrometry, ICP-OES analysis, and IR spectroscopy have been employed to confirm the structure and composition of the hexanuclear complex. Similar to the Li counterpart forming LiMn2O4 spinel material upon thermal decomposition, the title Na:Mn = 1:2 compound was utilized as the first single-source precursor for the low-temperature preparation of Na4Mn9O18 tunnel oxide. Importantly, four Mn sites in the hexanuclear molecule can be potentially partially substituted by other transition metals, leading to heterotri- and tetrametallic precursors for the advanced quaternary and quinary Na-ion oxide cathode materials.

Multi-functional Single-Source Molecular Precursors for Carbon-Coated Mixed-Metal Phosphates.

We introduce a new synthetic concept that can be broadly adopted for the low-temperature preparation of mixed-metal energy storage materials, such as phosphates, silicates, fluorides, fluorophosphates, and fluorosulfates that exhibit intrinsic low electronic conductivity and thus require a carbon modulation. The development of novel low-temperature approaches for assembling energy-related materials with a complex core-shell microstructure is of great importance for expanding their application scope. The traditional definition of single-source precursors refers to their ability to yield a phase-pure material upon thermal decomposition. We have developed a new way for the utilization of heterometallic molecular precursors in synthesis that goes beyond its common delineation as a single-phase maker. The utility of this approach has been demonstrated upon the low-temperature synthesis of lithium-iron phosphate@C, which represents a celebrated cathode material for Li-ion batteries. The first atomically precise carbonaceous molecular precursors featuring a desired Li:Fe:P ratio of 1:1:1, divalent iron, and sufficient oxygen content for the target LiFeIIPO4 phosphate were shown to enable a spontaneous formation of both the olivine core and conductive carbon shell, yielding a carbon-coated mixed-metal phosphate.

Intermetallic Compound Re2Ga9Ge with Re- and Ge-Embedded Gallium Clusters: Synthesis, Crystal Structure, Chemical Bonding, and Physical Properties.

Transition metal-based endohedral cluster intermetallic compounds are interesting electron phases, which frequently exhibit superconductivity with a peculiar interplay between the critical temperature and valence electron count. We present a new Re-based endohedral gallium cluster compound, Re2Ga9Ge. Its unique crystal structure (P42/mmc space group, a = 8.0452(3) Å, c = 6.7132(2) Å) is built by two types of gallium polyhedra: monocapped Archimedean antiprisms centered by rhenium atoms and tetrahedra containing a main-group element inside. The analysis of chemical bonding shows the presence of localized pairwise interactions between the p-block elements and the formation of multicenter bonds with the participation of d-orbitals of rhenium. In the electronic band structure, the Fermi level is located in a narrow pseudogap indicating the optimum band filling and thus explaining the virtual absence of a homogeneity range. The compound exhibits Pauli paramagnetism and metallic properties with unexpectedly low thermal conductivity. A sharp anomaly observed on the magnetic susceptibility and resistivity curves presumably indicates the electronic phase transition accompanied by charge ordering at the characteristic temperature of T * = 271 K in zero magnetic field.

Molecular and Supramolecular Structures of Triiodides and Polyiodobismuthates of Phenylenediammonium and Its N,N-dimethyl Derivative.

Despite remarkable progress in photoconversion efficiency, the toxicity of lead-based hybrid perovskites remains an important issue hindering their applications in consumer optoelectronic devices, such as solar cells, LED displays, and photodetectors. For that reason, lead-free metal halide complexes have attracted great attention as alternative optoelectronic materials. In this work, we demonstrate that reactions of two aromatic diamines with iodine in hydroiodic acid produced phenylenediammonium (PDA) and N,N-dimethyl-phenylenediammonium (DMPDA) triiodides, PDA(I3)2⋅2H2O and DMPDA(I3)I, respectively. If the source of bismuth was added, they were converted into previously reported PDA(BiI4)2⋅I2 and new (DMPDA)2(BiI6)(I3)⋅2H2O, having band gaps of 1.45 and 1.7 eV, respectively, which are in the optimal range for efficient solar light absorbers. All four compounds presented organic-inorganic hybrids, whose supramolecular structures were based on a variety of intermolecular forces, including (N)H⋅⋅⋅I and (N)H⋅⋅⋅O hydrogen bonds as well as I⋅⋅⋅I secondary and weak interactions. Details of their molecular and supramolecular structures are discussed based on single-crystal X-ray diffraction data, thermal analysis, and Raman and optical spectroscopy.

Protective Spinel Coating for Li1.17Ni0.17Mn0.50Co0.17O2 Cathode for Li-Ion Batteries through Single-Source Precursor Approach.

The Li1.17Ni0.17Mn0.50Co0.17O2 Li-rich NMC positive electrode (cathode) for lithium-ion batteries has been coated with nanocrystals of the LiMn1.5Co0.5O4 high-voltage spinel cathode material. The coating was applied through a single-source precursor approach by a deposition of the molecular precursor LiMn1.5Co0.5(thd)5 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) dissolved in diethyl ether, followed by thermal decomposition at 400 °C inair resulting in a chemically homogeneous cubic spinel. The structure and chemical composition of the coatings, deposited on the model SiO2 spheres and Li-rich NMC crystallites, were analyzed using powder X-ray diffraction, electron diffraction, high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy-dispersive X-ray (EDX) mapping. The coated material containing 12 wt.% of spinel demonstrates a significantly improved first cycle Coulombic efficiency of 92% with a high first cycle discharge capacity of 290 mAhg-1. The coating also improves the capacity and voltage retention monitored over 25 galvanostatic charge-discharge cycles, although a complete suppression of the capacity and voltage fade is not achieved.

Electron-Precise Semiconducting ReGa2Ge: Extending the IrIn3 Structure Type to Group 7 of the Periodic Table.

Intermetallic compounds with semiconducting properties are rare, but they give rise to advanced materials for energy conversion and saving applications. Here, we present ReGa2Ge, a new electron-precise narrow-gap intermetallic semiconductor. The compound crystallizes in the IrIn3 structure type (space group P42/mnm, a = 6.5734(3) Å, c = 6.7450(8) Å, and Z = 4), where Re atoms occupy the Ir site, while Ga and Ge jointly populate the In sites. 69,71Ga nuclear quadrupole resonance spectroscopy indicates nonstatistical partially ordered distribution of Ga and Ge over two available crystallographic sites; however, the Ga:Ge ratio is exactly 2:1 without noticeable homogeneity range. The stoichiometry of ReGa2Ge ensures its precise valence electron count, which is 17 e- per formula unit. Accordingly, a narrow energy gap opens up at the Fermi energy in the electronic structure. Electrical resistivity, Seebeck coefficient, and thermal conductivity are in agreement with the semiconducting behavior deduced from the electronic structure calculations and point to prospective thermoelectric properties at high temperatures. Bonding analysis reveals dominant covalency in Re-E (E = Ga, Ge) and Re-Re interactions.

Assembling Polyiodides and Iodobismuthates Using a Template Effect of a Cyclic Diammonium Cation and Formation of a Low-Gap Hybrid Iodobismuthate with High Thermal Stability.

Exploiting a template effect of 1,4-diazacycloheptane (also known as homopiperazine, Hpipe), four new hybrid iodides, (HpipeH2)2Bi2I10·2H2O, (HpipeH2)I(I3), (HpipeH2)3I6·H2O, and (HpipeH2)3(H3O)I7, were prepared and their crystal structures were solved using single crystal X-ray diffraction data. All four solid-state crystal structures feature the HpipeH22+ cation alternating with Bi2I104-, I3-, or I- anions and solvent water or H3O+ cation. HpipeH22+ assembles anionic and neutral building blocks into polymer structures by forming four strong (N)H···I and (N)H···O hydrogen bonds per cation, with the H···I distances ranging from 2.44 to 2.93 Å and H···O distances of 1.88-1.89 Å. These hydrogen bonds strongly affect the properties of compounds; in particular, in the case of (HpipeH2)2Bi2I10·2H2O, they ensure narrowing of the band gap down to 1.8 eV and provide high thermal stability up to 240 °C, remarkable for a hydrated molecular solid.

Heterotrimetallic Precursor with 2:2:1 Metal Ratio Requiring at Least a Pentanuclear Molecular Assembly.

This work represents an important step in the quest to make heteromultimetallic molecules featuring specific metal types and complicated metal ratios. The rational design, synthesis, and characterization of a complex heterotrimetallic single-source molecular precursor for the next generation sodium-ion battery cathode material, Na2Mn2FeO6, is described. A unique pentametallic platform [MnII(ptac)3-Na-MnIII(acac)3-Na-MnII(ptac)3] (1) was derived from the known polymeric structure of [NaMnII(acac)3]∞, through a series of elaborate design procedures, such as mixed-ligand, unsymmetric ligand, and mixed-valent approaches. Importantly, the application of those techniques results in a molecule with distinctively different transition metal positions in terms of ligand environment and oxidation states. An isovalent substitution of FeIII for the central MnIII ion forms the target heterotrimetallic precursor [MnII(ptac)3-Na-FeIII(acac)3-Na-MnII(ptac)3] (3) with an appropriate metal ratio of Na:Mn:Fe = 2:2:1. The arrangement of metal ions and ligands in this pentametallic assembly was confirmed by single crystal X-ray investigation. The unambiguous assignment of the positions and oxidation states of the Periodic Table neighbors Fe and Mn in 3 has been achieved by a combination of investigative techniques that include synchrotron resonant diffraction, X-ray multiwavelength anomalous diffraction, X-ray fluorescence spectroscopy, Mössbauer spectroscopy, and gas-phase DART mass spectrometry. The heterotrimetallic single-source precursor 3 was shown to exhibit a clean decomposition pattern yielding the phase-pure P2-Na2Mn2FeO6 quaternary oxide with high uniformity of metal ion distribution as confirmed by electron microscopy.

Heterotrimetallic Mixed-Valent Molecular Precursors Containing Periodic Table Neighbors: Assignment of Metal Positions and Oxidation States.

A known trinuclear structure was used to design the heterobimetallic mixed-valent, mixed-ligand molecule [CoII (hfac)3 -Na-CoIII (acac)3 ] (1). This was used as a template structure to develop heterotrimetallic molecules [CoII (hfac)3 -Na-FeIII (acac)3 ] (2) and [NiII (hfac)3 -Na-CoIII (acac)3 ] (3) via isovalent site-specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple-wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of 2 and 3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform 1 exhibits flexibility in accommodating a variety of di- and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM'O4 functional oxide materials.

Endohedral Cluster Superconductors in the Mo-Ga-Sn System Explored by the Joint Flux Technique.

Endohedral Ga cluster compounds feature nontrivial superconducting states including the two-gap superconductivity similar in nature to MgB2. We use the joint flux synthetic technique to introduce Sn into the Ga matrix and tune the valence electron count in the two new endohedral cluster superconductors Mo8Ga41-xSnx and Mo4Ga21-x-δSnx with critical temperatures of Tc = 8.7 and 5.85 K, respectively. While the former compound is a derivative of the previously known Mo8Ga41 superconductor, where Sn atoms are enclosed inside the Sn@Ga6 octahedral clusters, the latter is a new architecture built upon Mo@Ga9Sn clusters, Ga@Ga12 cuboctahedra, and Sn4 squares. We show that this novel Mo4Ga21-x-δSnx superconductor features strong electron-phonon coupling with the large ratio of 2Δ(0)/(kBTc) = 4.1 similar to that of the Mo8Ga41 superconductor with the closely related crystal structure.

From lithium to sodium: design of heterometallic molecular precursors for the NaMO2 cathode materials.

Based on the well-established model structure of Li2M2(tbaoac)6, the first series of heterometallic molecular precursors Na2M2(tbaoac)6(THF)2 (M = Fe, Co, and Ni) have been designed and successfully utilized for the preparation of NaMO2 oxide cathode materials of sodium-ion batteries.

From a volatile molecular precursor to twin-free single crystals of bismuth.

A highly volatile molecular precursor, dibismuth(ii) (tetra)trifluoroacetate, was successfully utilized for the gas phase growth of twin-free single crystals of bismuth. This allowed high-quality single-crystal X-ray diffraction data to be collected, providing accurate structural parameters for elemental bismuth under ambient conditions.

From endohedral cluster superconductors to approximant phases: synthesis, crystal and electronic structure, and physical properties of Mo8Ga41-xZnx and Mo7Ga52-xZnx.

Using the crystal-growth joint flux technique based on the combination of two aliovalent low-melt metals, gallium and zinc, we adjust the gross valence electron count in the Mo-Ga-Zn system and produce the Mo8Ga41-xZnx and Mo7Ga52-xZnx intermetallic compounds. Gradual reduction in the valence electron count first leads to the Zn for Ga substitution in the Mo8Ga41 endohedral cluster superconductor, accompanied by the formation of Zn-containing clusters in the crystal structure and by the gradual suppression of superconductivity. Mo8Ga41-xZnx with x = 7.2(2) exhibits superconducting properties below TC = 4 K, whereas there is no superconducting transition at temperatures above 2 K for the limiting composition of x = 11.3(2). Further, the Mo7Ga52-xZnx phase is formed from the flux with a higher content of Zn. Mo7Ga52-xZnx crystallizes in the Mo7Sn12Zn40 structure type with a narrow homogeneity range and exhibits metallic behavior with no sign of superconductivity down to at least 1.8 K. Its experimental valence electron count of 2.9 e per atom is below that of endohedral gallium cluster superconductors. Electronic structures of Mo8Ga41-xZnx and Mo7Ga52-xZnx feature the opening of a pseudogap slightly below the Fermi level indicating the specific stability of these structure types at the valence electron count of 3.2 e per atom and 2.7 e per atom, respectively.

Three to tango requires a site-specific substitution: heterotrimetallic molecular precursors for high-voltage rechargeable batteries.

Design of heterotrimetallic molecules, especially those containing at least two different metals with close atomic numbers, radii, and the same coordination number/environment is a challenging task. This quest is greatly facilitated by having a heterobimetallic parent molecule that features multiple metal sites with only some of those displaying substitutional flexibility. Recently, a unique heterobimetallic complex LiMn2(thd)5 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been introduced as a single-source precursor for the preparation of a popular spinel cathode material, LiMn2O4. Theoretical calculations convincingly predict that in the above trinuclear molecule only one of the Mn sites is sufficiently flexible to be substituted with another 3d transition metal. Following those predictions, two heterotrimetallic complexes, LiMn2-x Co x (thd)5 (x = 1 (1a) and 0.5 (1b)), that represent full and partial substitution, respectively, of Co for Mn in the parent molecule, have been synthesized. X-ray structural elucidation clearly showed that only one transition metal position in the trinuclear molecule contains Co, while the other site remains fully occupied by Mn. A number of techniques have been employed for deciphering the structure and composition of heterotrimetallic compounds. Synchrotron resonant diffraction experiments unambiguously assigned 3d transition metal positions as well as provided a precise "site-specific Mn/Co elemental analysis" in a single crystal, even in an extremely difficult case of severely disordered structure formed by the superposition of two enantiomers. DART mass spectrometry and magnetic measurements clearly confirmed the presence of heterotrimetallic species LiMnCo(thd)5 rather than a statistical mixture of two heterobimetallic LiMn2(thd)5 and LiCo2(thd)5 molecules. Heterometallic precursors 1a and 1b were found to exhibit a clean decomposition yielding phase-pure LiMnCoO4 and LiMn1.5Co0.5O4 spinels, respectively, at the relatively low temperature of 400 °C. The latter oxide represents an important "5V spinel" cathode material for the lithium ion batteries. Transmission electron microscopy confirmed a homogeneous distribution of transition metals in quaternary oxides obtained by pyrolysis of single-source precursors.

Crystal Growth of Intermetallics from the Joint Flux: Exploratory Synthesis through the Control of Valence Electron Count.

In this study, we modify the flux-growth method for the purpose of exploratory synthesis of ternary intermetallic compounds. Our concept is based on the assumption that valence electron count plays a crucial role in the stability of polar intermetallic compounds of different structure types. Control of the valence electron count parameter is made possible through the use of an excess of two metals having a different number of valence electrons. By gradually changing the ratio between these metals in the joint flux, we scan the gross number of valence electrons and explore the crystallization of new compounds. In the ternary system Re-Ga-Zn, we detect compounds belonging to three structure types, ReGa5, PtHg4, and V8Ga41, while gradually increasing the content of Zn metal in the flux. Two new compounds, ReGa3Zn and Re8Ga41- xZn x with x = 21.2(5), are obtained in the form of high-quality single crystals, and the former compound shows the narrow-gap semiconducting behavior favorable for high thermoelectric performance.

A three body problem: a genuine heterotrimetallic molecule vs. a mixture of two parent heterobimetallic molecules.

This work raises a fundamental question about the "real" structure of molecular compounds containing three different metals: whether they consist of genuine heterotrimetallic species or of a mixture of parent heterobimetallic species. Heterotrimetallic complex Li2CoNi(tbaoac)6 (1, tbaoac = tert-butyl acetoacetate) has been designed based on the model tetranuclear structure featuring two transition metal sites in order to be utilized as a molecular precursor for the low-temperature preparation of the LiCo0.5Ni0.5O2 battery cathode material. An investigation of the structure of 1 appeared to be very challenging, since the Co and Ni atoms have very similar atomic numbers, monoisotopic masses, and radii as well as the same oxidation state and coordination number/environment. Using a statistical analysis of heavily overlaid isotope distribution patterns of the [Li2MM'L5]+ (M/M' = Co2, Ni2, and CoNi) ions in DART mass spectra, it was concluded that the reaction product 1 contains both heterotrimetallic and bimetallic species. A structural analogue approach has been applied to obtain Li2MMg(tbaoac)6 (M = Co (2) and Ni (3)) complexes that contain lighter, diamagnetic magnesium in the place of one of the 3d transition metals. X-ray crystallography, mass spectrometry, and NMR spectroscopy unambiguously confirmed the presence of three types of molecules in the reaction mixture that reaches an equilibrium, Li2M2L6 + Li2Mg2L6 ↔ 2Li2MMgL6, upon prolonged reflux in solution. The equilibrium mixture was shown to have a nearly statistical distribution of the three molecules, and this is fully supported by the results of theoretical calculations revealing that the stabilization energies of heterotrimetallic assemblies fall exactly in between those for the parent heterobimetallic species. The LiCo0.5Ni0.5O2 quaternary oxide has been obtained in its phase-pure form by thermal decomposition of heterometallic precursor 1 at temperatures as low as 450 °C. Its chemical composition, structure, morphology, and transition metal distribution have been studied by X-ray and electron diffraction techniques and compositional energy-dispersive X-ray mapping with nanometer resolution. The work clearly illustrates the advantages of heterometallic single-source precursors over the corresponding multi-source precursors.

Expanding the Structural Motif Landscape of Heterometallic ß-Diketonates: Congruently Melting Ionic Solids.

The first example of ionic ß-diketonates in which both the cation and anion are octahedral coordinatively saturated metal diketonate moieties are reported. Heterometallic tin-transition-metal heteroleptic diketonates were obtained through solid-state redox reactions and are formulated as {[SnIV(thd)3]+[MII(hfac)3]-} (MII = Mn (1), Fe (2), Co (3); thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, hfac = hexafluoroacetylacetonate). X-ray single-crystal structural investigations along with DART mass spectrometry, multinuclear NMR, and magnetic susceptibility measurements have been used to confirm an assignment of metal oxidation states in compounds 1-3. Ionic compounds were found to melt congruently at temperatures below the decomposition point. As such, they represent prospective materials that can be utilized as ionic liquids as well as reagents for the soft transfer of diketonate ligands. An unexpected volatility of ionic compounds 1-3 was proposed to occur through a transport reaction, in which the transport agent is one of the products of their partial decomposition in the gas or condensed phase.