Synthesis of imidazolium-based pentacoordinated organofluorosilicate and germanate salts.

The syntheses of a new triphenyldifluorogermanate and various pentacoordinated organofluorosilicates are presented. The fluorogermane and fluorosilane compounds were obtained from the corresponding chlorosilanes and chlorogermane by halogen substitution with KF. Subsequent reaction with the imidazolium-based fluoride reagent [IPrH][F] (1,3-bis(2,6-diisopropylphenyl)imidazolium fluoride) led to the formation of [IPrH][Ph3SiF2] (1), [IPrH][Ph2SiF3] (3), [IPrH][Et2SiF3] (4), [IPrH][PhSiF4] (5), [IPrH][EtSiF4] (6) and [IPrH][Ph3GeF2] (7). All the products obtained were characterised by NMR, Raman spectroscopy and X-ray diffraction. The results were supported by DFT calculations of the structurally optimised compounds.

Trideset let delovanja Sole eksperimentalne kemije na Institutu "Jozef Stefan": trideset let motiviranja mladih generacij in utrjevanja poti naravoslovnega izobrazevanja.

Pred 30. leti, natancneje spomladi leta 1992, je bila, v okviru Odseka za anorgansko kemijo in tehnologijo Instituta "Jozef Stefan", ustanovljena Sola eksperimentalne kemije. Zaradi razvoja znanosti in interdisciplinarnih pristopov, je njen glavni namen priblizevanje kemije mladim generacijam in prikazovanje njene sirse uporabe v vsakdanjem zivljenju. Sola eksperimentalne kemije tako ustvarja pomemben most med raziskovanjem in izobrazevanjem ter aktivno prispeva k popularizaciji predmetnega podrocja v solah.

Coordination of a Neutral Ligand to a Metal Center of Oxohalido Anions: Fact or Fiction?

Can a neutral ligand bond to a metal center of a square pyramidal oxohalido anion at the available sixth octahedral position? Crystal structures of some compounds indeed suggest that ligands, such as THF, pyridine, H2O, NH3, and CH3CN, can interact with the central metal atom, because they are oriented with their heteroatom toward the metal center with distances being within the bonding range. However, this assumption that is based on chemical intuition is wrong. In-depth analysis of interactions between ligands and oxohalido anions (e.g., VOX4-, NbOCl4-) reveals that the bonding of a neutral ligand is almost entirely due to electrostatic interactions between the H atoms of a ligand and halido atoms of an anion. Furthermore, ab initio calculations indicate that the ligand-VOF4- interactions represent only about one-quarter of the total binding of the ligand within the crystal structure, whereas the remaining binding is due to crystal packing effects. The current study therefore shows that relying solely on the structural aspects of solved crystal structures, such as ligand orientation and bond distances, can lead to the wrong interpretation of the chemical bonding.

Reactivity of VOF3 with N-Heterocyclic Carbene and Imidazolium Fluoride: Analysis of Ligand-VOF3 Bonding with Evidence of a Minute π Back-Donation of Fluoride.

Reaction of vanadium(V) oxide trifluoride (VOF3) and the new "naked" fluoride reagent [(LDipp)H][F] (LDipp = 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2 H-imidazol-2-ylidene) leads to the isolation of [(LDipp)H][VOF4] (1) where the long sought discrete [VOF4]- anion was finally obtained. The neutral [(LDipp)VOF3] (2) complex was synthesized by a similar reaction between VOF3 and bulky N-heterocyclic carbene (NHC) ligand LDipp. In this context, we analyzed, by means of DFT calculations, intermolecular interactions between [(LDipp)VOF3] (2) complexes in the crystal structure and realized that these interactions have a significant effect on the V-Ftrans bond length. We further scrutinized ligand bonding within [(LDipp)VOF3] (2) and related complexes, because, in this kind of complexes, a rather short distance between CNHC and cis-halogen atoms has spurred some discussion about the type of interactions between them. We provide evidence of a minute π back-bonding into NHC ligands, which is larger for chloride [(NHC)VOCl3] than fluoride [(NHC)VOF3] complexes, although the fluoride ions are, counterintuitively and to a larger degree, involved in back-bonding than chloride ions. The influence of π back-bonding on V-Ftrans and V-Fcis bond lengths was also rationalized. Finally, the hydrolysis of [(LDipp)VOF3] (2) product was studied and [(LDipp)H][VO2F2] (3) salt was obtained and characterized as the most stable product in this system.

Discrete GeF5- Anion Structurally Characterized with a Readily Synthesized Imidazolium Based Naked Fluoride Reagent.

The recently prepared novel naked fluoride reagent 1,3-bis(2,6-diisopropylphenyl)imidazolium fluoride ([(LDipp)H][F]), treated with an excess of MF4 (M = Si, Ge), results in isolation of [(LDipp)H][MF5] products with the elusive trigonal bipyramidal MF5- anions. Specific steric characteristics of the [(LDipp)H]+ cation readily support isolation of monomeric and discrete trigonal bipyramidal fluorido anions of silicon and germanium. Based on combination of experimental results and DFT calculations, we demonstrate that the role of bulky cation is not solely due to steric hindering but also due to electrostatic effects, which are important in the design of such uncommon species. The discrete GeF5- anion was characterized by X-ray single-crystal diffraction for the first time. We report the missing 19F NMR entries for the discrete GeF5- and GeF62- anions in acetonitrile. All the products were also characterized by Raman spectroscopy and elemental analysis and supported by quantum-mechanical calculations.

Oxidation of Ruthenium and Iridium Metal by XeF2 and Crystal Structure Determination of [Xe2F3][RuF6]·XeF2 and [Xe2F3][MF6] (M = Ru, Ir).

Salts containing [Xe2F3]+ cations and [MF6]- anions (M = Ru, Ir) were synthesized by the oxidation of metal with excess of XeF2 in anhydrous hydrogen fluoride (aHF) as a solvent. Single crystals of [Xe2F3][RuF6]·XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6] were grown by slow evaporation of the solvent. [Xe2F3][RuF6]·XeF2 crystallizes in a triclinic P-1 space group (a = 8.3362(1) Å, b = 8.8197(2) Å, c = 9.3026(4) Å; α = 68.27(1)°, ß = 63.45(1)°, γ = 82.02°, V = 568.09(9) Å3 (Z = 2)). Discrete [Xe2F3]+, XeF2 and [RuF6]- units are found in the asymmetric unit. [Xe2F3][RuF6] and [Xe2F3][IrF6] compounds are isostructural and crystallize in a monoclinic Cc space group (a = 14.481(3) Å (Ru); 14.544(3) Å (Ir); b = 8.0837(8) Å (Ru), 8.0808(7) Å (Ir), c = 10.952(2) Å (Ru), 11.014(2) Å (Ir); ß = 136.825(6)° (Ru), 139.954(7)°, V = 877.2(3) Å3 (Ru), 883.6(3) Å3 (Ir); Z = 4). The asymmetric unit in the [Xe2F3][MF6] (M = Ru, Ir) consists of one [Xe2F3]+ and one [MF6]- unit.

Synthesis and crystal structures of lanthanoid(III) hexafluoroarsenates with AsF3 ligands.

Lanthanoid(III) hexafluoroarsenates with AsF3 as a ligand were prepared with the reactions of solutions of Ln(AsF6)3 in anhydrous hydrogen fluoride and AsF3. Solid products with composition Ln(AsF3)3(AsF6)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Er, Tm) were isolated at 233 K. The attempt to prepare corresponding Yb and Lu compounds failed. Single crystals of Ln(AsF3)3(AsF6)3 (Ln = Ce, Pr) were prepared by the reaction of LnF3 (Ln = Ce, Pr) with AsF5 and aHF under solvothermal conditions above critical temperature of AsF5. During the crystallization the reduction of some AsF5 occurred and AsF3 was formed. Compounds crystallize in a hexagonal crystal system, space group P 6- 2c (a = 10.6656(7) Å (Ce); 10.6383(7) Å (Pr); c = 10.9113(9) Å (Ce), 10.878(2) Å (Pr); V = 1074.9(1) Å3 (Ce), 1066.2(2) Å3 (Pr); Z = 2). Ln atoms are coordinated by nine fluorine atoms in the shape of the tri-capped trigonal prism and are further connected in three-dimensional framework via trans bridging AsF6 units. Three fluorine atoms are provided by AsF3 (capped positions) and six by AsF6 units. X-ray powder analysis of Ln(AsF3)3(AsF6)3 (Ln = La, Nd, Sm, Eu, Gd, Tb, Er, Tm) show that they are isostructural with corresponding Ce and Pr compounds.

Solid-state NMR spectroscopic study of coordination compounds of XeF(2) with metal cations and the crystal structure of [Ba(XeF(2))(5)][AsF(6)](2).

The coordination compounds [Mg(XeF(2))(2)][AsF(6)](2), [Mg(XeF(2))(4)][AsF(6)](2), [Ca(XeF(2))(2.5)][AsF(6)](2), [Ba(XeF(2))(3)][AsF(6)](2), and [Ba(XeF(2))(5)][AsF(60](2) were characterized by solid-state (19)F and (129)Xe magic-angle spinning NMR spectroscopy. The (19)F and (129)Xe NMR data of [Mg(XeF(2))(2)][AsF(6)](2), [Mg(XeF(2)(4)][AsF(6)](2), and [Ca(XeF(2))(2.5)][AsF(6)](2) were correlated with the previously determined crystal structures. The isotropic (19)F chemical shifts and (1)J((129)Xe-(19)F) coupling constants were used to distinguish the terminal and bridging coordination modes of XeF(2). Chemical-shift and coupling-constant calculations for [Mg(XeF(2))(4)][AsF(6)](2) confirmed the assignment of terminal and bridging chemical-shift and coupling-constant ranges. The NMR spectroscopic data of [Ba(XeF(2))(3)][AsF(6)](2) and [Ba(XeF(2))(5)][AsF(6)](2) indicate the absence of any terminal XeF(2) ligands, which was verified for [Ba(XeF(2))(5)][AsF(6)](2) by its X-ray crystal structure. The adduct [Ba(XeF(2))(5)][AsF(6)](2) crystallizes in the space group Fmmm, with a = 11.6604(14) Angstrom, b = 13.658(2) Angstrom, c = 13.7802(17) Angstrom, V = 2194.5(5) Angstrom(3) at -73 degrees C, Z = 4, and R = 0.0350 and contains two crystallographically independent bridging XeF(2) molecules and one nonligating XeF(2) molecule. The AsF(6-) anions in [Mg(XeF(2))(4)][AsF(6)](2), [Ca(XeF(2))(2.5)][AsF(6)](2), [Ba(XeF(2))(3)][AsF(6)](2), and [Ba(XeF(2))(5)][AsF(6)](2) were shown to be fluxional with the fluorines-on-arsenic being equivalent on the NMR time scale, emulating perfectly octahedral anion symmetry.

Metal(II) hexafluorophosphates(V) (M = Sr, Pb) containing XeF(2)-coordinated metal ions [M(XeF(2))(3)](PF(6))(2), [Pb(3)(XeF(2))(11)](PF(6))(6), and [Sr(3)(XeF(2))(10)](PF(6))(6).

From the system MF(2)/PF(5)/XeF(2)/anhydrous hydrogen fluoride (aHF), four compounds [Sr(XeF(2))(3)](PF(6))(2), [Pb(XeF(2))(3)](PF(6))(2), [Sr(3)(XeF(2))(10)](PF(6))(6), and [Pb(3)(XeF(2))(11)](PF(6))(6) were isolated and characterized by Raman spectroscopy and X-ray single-crystal diffraction. The [M(XeF(2))(3)](PF(6))(2) (M = Sr, Pb) compounds are isostructural with the previously reported [Sr(XeF(2))(3)](AsF(6))(2). The structure of [Sr(3)(XeF(2))(10)](PF(6))(6) (space group C2/c; a = 11.778(6) Angstrom, b = 12.497(6) Angstrom, c = 34.60(2) Angstrom, beta = 95.574(4) degrees, V = 5069(4) Angstrom(3), Z = 4) contains two crystallographically independent metal centers with a coordination number of 10 and rather unusual coordination spheres in the shape of tetracapped trigonal prisms. The bridging XeF(2) molecules and one bridging PF(6)- anion, which connect the metal centers, form complicated 3D structures. The structure of [Pb(3)(XeF(2))(11)](PF(6))(6) (space group C2/m; a = 13.01(3) Angstrom, b = 11.437(4) Angstrom, c = 18.487(7) Angstrom, beta = 104.374(9) degrees, V = 2665(6) Angstrom(3), Z = 2) consists of a 3D network of the general formula {[Pb(3)(XeF(2))(10)](PF(6))(6)}n and a noncoordinated XeF(2) molecule fixed in the crystal structure only by weak electrostatic interactions. This structure also contains two crystallographically independent Pb atoms. One of them possesses a unique homoleptic environment built up by eight F atoms from eight XeF(2) molecules in the shape of a cube, whereas the second Pb atom with a coordination number of 9 adopts the shape of a tricapped trigonal prism common for lead compounds. [Pb(3)(XeF(2))(11)](PF(6))(6) and [Sr(3)(XeF(2))(10)](PF(6))(6) are formed when an excess of XeF(2) is used during the process of the crystallization of [M(XeF(2))(3)](PF(6))(2) from their aHF solutions.

Coordination of XeF2 to calcium and cadmium hexafluorophosphates(V).

[M(XeF2)5](PF6)2 (M = Ca, Cd) complexes were prepared by the reaction of MF2 and XeF2 under pressure of gaseous PF5 in anhydrous HF as solvent. The coordination sphere of the Ca atom consists of nine fluorine atoms: three from two PF6(-) units (one bidentate and one monodentate) and one from each of six XeF2 molecules. The coordination sphere of the Cd atom consists of eight fluorine atoms: one from each of two PF6(-) units and one from each of six XeF2 molecules. Two of the XeF2 ligands about M in each compound are bridging ligands and are each linked to two M, generating infinite (-M-F-Xe-F-M-F-Xe-F-) chains along the b-axis in the Ca salt and along the c-axis in the Cd compound. The Cd2+ cation is smaller and more electronegative than the Ca2+ cation. These differences account for the higher F ligand coordination in the Ca2+ salt and for other structural features that distinguish them. The different stoichiometry of the PF6(-) salts when compared with their AsF6(-) analogues, which have the composition [M(XeF2)4](AsF6)2 (M = Ca, Cd), is in accord with the lower F ligand charge in the AsF6(-) when compared with that in the PF6(-) compound. Indeed, the AsF6(-) ligand charges appear to be similar to those in the XeF2-bridged species.

[Mg(XeF(2))(n)()](AsF(6))(2) (n = 4, 2): first compounds of magnesium with XeF(2).

The reaction between Mg(AsF(6))(2) and XeF(2) in anhydrous HF (aHF) at room temperature yields two compounds with XeF(2) bonded directly to the Mg(2+) cation: [Mg(XeF(2))(4)](AsF(6))(2); [Mg(XeF(2))(2)](AsF(6))(2). The 1:4 compound is obtained with excess XeF(2) while the 1:2 compound is prepared from stoichiometric amounts of Mg(AsF(6))(2) and XeF(2). [Mg(XeF(2))(4)](AsF(6))(2) crystallizes in an orthorhombic crystal system, space group P2(1)2(1)2(1), with a = 8.698(15) A, b = 14.517(15) A, c = 15.344(16) A, V = 1937(4) A(3), and Z = 4. The octahedral coordination sphere of Mg consists of one fluorine atom from each of the four XeF(2) molecules and two fluorine atoms from the two AsF(6) units. [Mg(XeF(2))(2)](AsF(6))(2) crystallizes in the orthorhombic crystal system, space group Pbam, with a = 8.9767(10) A, b = 15.1687(18) A, c = 5.3202(6) A, V = 724.42(14) A(3), and Z = 2. The octahedral coordination sphere consists of two fluorine atoms, one from each of the two XeF(2) molecules and four fluorine atoms from the four bridging AsF(6) units.