Computational Study of spx(x=1–3)-Hybridized Be−Be Bonds Stabilized by Amidinate Ligands

Complexes containing odd-electron Be−Be bonds are still rare until now. Hereby, a series of neutral di-beryllium amidinate complexes containing a Be−Be bond were explored theoretically. The complexes with direct chelation with the Be₂ dimer by the bidentate amidinate (AMD) ligands are always corresponding to their global minimum structures. The detailed bonding analyses reveal that the localized electrons of the Be−Be fragment can be adjusted by the amount of AMD ligands because each AMD ligand only takes one electron from the Be₂ fragment. Meanwhile, the hybridization of the central Be atom also changes as the number of AMD ligands increases. In particular, the sp³-hybridized single-electron Be−Be bond is firstly identified in the tri-AMD-ligands-chelated neutral D_3h- Be₂(AMD)₃ complex, which also possesses the higher stability compared to its monoanionic D_3h- Be₂(AMD)₃ ⁻ and monocationic C₃- Be₂(AMD)₃ ⁺ analogues. Importantly, our study provides a new approach to obtain a neutral odd-electron Be−Be bond, namely by the use of radical ligands through side-on chelation.     

The Beryllium Pentamer: Trailing an Uneven Sequence of Dissociation Energies

Recent high‐resolution spectroscopic studies by Merritt, Bondybey, and Heaven (Science 2009 , 324, 1548) have heightened the anticipation that small beryllium clusters will soon be observed in the laboratory. Beryllium clusters are important discrete models for the theoretical study of metals. The trigonal bipyramidal Be₅ molecule is studied using high‐level coupled cluster methods. We obtain the optimized geometry, atomization and dissociation energies, and vibrational frequencies. The c～CCSDT(Q) method is employed to compute the atomization and dissociation energies. In this approach, complete basis set (CBS) extrapolations at the CCSD(T) level of theory are combined with an additive correction for the effect of iterative triple and perturbative quadruple excitations. Harmonic vibrational frequencies are obtained using analytic gradients computed at the CCSD(T) level of theory. We report an atomization energy of 129.6 kcal mol^?1 at the trigonal bipyramid global minimum geometry. The Be₅→Be₄+Be dissociation energy is predicted to be 39.5 kcal mol^?1. The analogous dissociation energies for the smaller beryllium clusters are 64.0 kcal mol^?1 (Be₄→Be₃+Be), 24.2 kcal mol^?1 (Be₃→Be₂+Be), and 2.7 kcal mol^?1 (Be₂→Be+Be). The trigonal bipyramidal Be₅ structure has an equatorial–equatorial bond length of 2.000 Å and an axial–equatorial distance of 2.060 Å. Harmonic frequencies of 730, 611, 456, 583, 488, and 338 cm^?1 are obtained at the CCSD(T)/cc‐pCVQZ level of theory. Quadruple excitations are found to make noticeable contributions to the energetics of the pentamer, which exhibits a significant level of static correlation.     

Ultra-Weak Metal−Metal Bonding: Is There a Beryllium-Beryllium Triple Bond?

Metal-metal triple bonds featuring s-block element have not been reported until now. Only Be−Be double bonds between have been predicted theoretically based on the intuitive electron donation from four s¹ type electron-donating ligands. Herein, we theoretically predicted a novel species featuring a Be−Be triple bond in the Li₆Be₂ molecule. The molecule was found to be thermodynamically stable. The presence of the triple bond was confirmed by adaptive natural density partitioning (AdNDP), electron localization function (ELF), and atoms in molecules (AIM) analyses. Moreover, the mechanical strength of the Be−Be triple bond was analyzed by using compliance matrix, pointing towards its ultra-weak nature.     

From Very Strong to Inexistent Be−Be Bonds in the Interactions of Be2 with π-Systems

Isolated Be₂ is a typical example of a weakly bound system, but interaction with other systems may give rise to surprising bonding features. The interactions between Be₂ and a set of selected neutral C_nH_n (n=2–8) π-systems have been analyzed through the use of G4 and G4MP2 ab initio methods, along with multireference CASPT2//CASPT2 calculations. Our results systematically show that the C_nH_n−Be₂−C_nH_n clusters formed are always very stable. However, the nature of this interaction is completely different when the π-system involved is a closed shell species (n=2, 4, 6, 8), or a radical (n=3, 5, 7). In the first case, the interaction does not occur with the π-system as a whole, but with specific C centers yielding rather polar but strong C−Be bonds. Nonetheless, although the Be−Be distances in these complexes are similar to the ones in compounds with ultra-strong Be−Be bonds, a close examination of their electron density distribution reveals that no Be−Be bonds exist. The situation is totally different when the interaction involves two π-radicals, C_nH_n−Be₂−C_nH_n (n=3, 5, 7). In these cases, a strong Be−Be bond is formed. Indeed, even though Be is electron deficient, the Be₂ moiety behaves as an efficient electron donor towards the two π-radicals, so that the different C_nH_n−Be₂−C_nH_n (n=3, 5, 7) clusters are the result of the interaction between Be₂²⁺ and two L⁻ anions. The characteristics of these two scenarios do not change when dealing with bicyclic π-compounds, such as naphthalene and pentalene, because the interaction with the Be₂ moiety is localized on one of the unsaturated cycles, the other being almost a spectator.     

Kristallstrukturen und chemische Bindung von AM2GeSe4 (A = Sr,Ba; M = Cu,Ag)

New Noncentrosymmetric Selenogermanates. I. Crystal Structures and Chemical Bonding of AM ₂GeSe₄ ( A = Sr, Ba; M = Cu, Ag) Three new quaternary selenogermanates were synthesized by heating the elements at 983–1073 K. Their crystal structures were determined by single crystal X‐ray methods. The dark red semiconductors crystallize in noncentrosymmetric space groups. SrCu₂GeSe₄ (Ama2, a = 10.807(4) Å, b = 10.735(4) Å, c = 6.541(2) Å, Z = 4) forms a new structure type, whereas BaCu₂GeSe₄ (P3₁, a = 6.490(1) Å, c = 16.355(3) Å, Z = 3) and BaAg₂GeSe₄ (I222, a = 7.058(1) Å, b = 7.263(1) Å, c = 8.253(2) Å, Z = 2) crystallize in structures known from thiostannates. Main structural features are almost regular GeSe₄‐, but distorted CuSe₄‐ or AgSe₄‐tetrahedra sharing corners or edges. Eight selenium atoms coordinate the alkaline earth atoms in the voids of these three dimensional tetrahedral networks. Chemical bonding and the electronic structure are elucidated by self‐consistent band structure calculations and the COHP method. The electron density and the electron localization function ELF of SrCu₂GeSe₄ reveal a significant stronger covalent character for the Ge–Se bonds compared with the Cu–Se bonds. For this reason the GeSe₄ tetrahedra appear as quasi molecular entities, arranged spatially according to the motifs of closest packing. The metal atoms occupy the tetrahedral and octahedral voids of these “tetrahedra packing”. This concept allows to derive the structures of AM₂GeSe₄‐compounds from simple binary structure types as Li₃Bi or Ni₂In.     

Aurophilic interactions in μ‐p‐phenyl­enediethynyl‐bis[(trimethyl phosphite)gold(I)] dichloro­methane hemisolvate

The title compound, [Au₂(C₁₀H₄)(C₃H₉O₃P)₂]·0.5CH₂Cl₂, is a linear monomer in which each Au atom is coordinated by one acetylene and one phosphite group. Molecules are connected through aurophilic interactions, one short and one longer, approximately perpendicular to the intramolecular di(gold acetylide) unit, with an Au⋯Au(x, 1 − y, + z) distance of 3.1733 (2) Å and an Au⋯Au(−x, y, − z) distance of 3.5995 (3) Å. Comparison with related compounds exhibiting aurophilic interactions shows that the packing architecture is not determined by steric factors alone.     

Extraction and isolation of the One-electron Oxidized [(Zr6Be)Cl18]5− and [(Zr6Be)Cl18]4− Clusters from solid state precursors

One-electron oxidized zirconium chloride clusters were obtained from solid state precursors Rb₅Zr₆Cl₁₈B and K₃Zr₆Cl₁₅Be by dissolution in CH₃CN in the presence of Et₄NCl and isolated as the salts (Et₄N)₄Zr₆Cl₁₈B · 2 CH₃CN and (Et₄N)₅Zr₆Cl₁₈Be · 3 CH₃CN. (Et₄N)₄Zr₆Cl₁₈B · 2 CH₃CN crystallizes in the space group P1 (#2) with a = 12.329(5) Å, b = 12.657(6) Å, c = 13.136(8) Å, α = 118.28(4)°, β = 93.45(4)°, γ = 105.54(3)°, V = 1696(2) ų, and Z = 1. (Et₄N)₅Zr₆Cl₁₈Be · 3 CH₃CN was refined in the space group C2/c (# 15) with a = 24.166(11) Å, b = 13.265(6) Å, c = 25.86(2) Å, β = 104.21(4)°, V = 8037(7) ų, and Z = 4; the space group reflects the pseudo-symmetry of the crystal, the true symmetry of the structure is lower. The removal of one electron from the Zr? Zr bonding HOMO of both clusters results in cluster expansion of similar magnitude in both compounds. Moisture from the added Et₄NCl is the likely oxidant, but the possibility that acetonitrile may be reduced by [(Zr₆Be)Cl₁₈]^6? is not ruled out.     

Synthesis and characterization of a new organically templated open-framework beryllium phosphite with 3, 4-connected networks

Employing diethylenetriamine (=dien) as a structure-directing agent, a new open-framework beryllium phosphite H₂dien·Be₃(HPO₃)₄ (1), has been synthesized hydrothermally and structurally characterized by single crystal X-ray diffraction. The structure of 1 features a (3, 4)-connected framework with 8- and 12-ring channels, which is constructed from strictly alternating BeO₄ tetrahedra and HPO₃²⁻ pseudopyramids. The 3-D framework possesses a pcu topology when the heptameric [Be₃(HPO₃)₄] clusters are regarded as 6-connected secondary building units. Crystal data: 1, monoclinic, C2/c (no. 15), a = 8.7350(3) Å, b = 15.1704(6) Å, c = 13.0851(4) Å, β = 101.223(5)°, V = 1700.79(10) Å³, Z = 4, R₁ = 0.0625, wR₂ = 0.1692.     

Searching new structures of beryllium-doped in small-sized magnesium clusters: Be2MgnQ (Q = 0, −1; n = 1–11) clusters DFT study

Using CALYPSO method to search new structures of neutral and anionic beryllium-doped magnesium clusters followed by density functional theory (DFT) calculations, an extensive study of the structures, electronic and spectral properties of Be₂Mg_n^Q (Q = 0, −1; n = 2–11) clusters is performed. Based on the structural optimization, it is found that the Be₂Mg_n^Q (Q = 0, −1) clusters are shown by tetrahedral-based geometries at n = 2–6 and tower-like-based geometries at n = 7–11. The calculations of stability indicate that Be₂Mg₅^Q=0, Be₂Mg₅^Q=−1, and Be₂Mg₈^Q=−1 clusters are “magic” clusters with high stability. The NCP shows that the charges are transferred from Mg atoms to Be atoms. The s- and p-orbitals interactions of Mg and Be atoms are main responsible for their NEC. In particular, chemical bond analysis including molecular orbitals (MOs) and chemical bonding composition for magic clusters to further study their stability. The results confirmed that the high stability of these clusters is due to the interactions between the Be atom and the Mg₅ or Mg₈ host. Finally, theoretical calculations of infrared and Raman spectra of the ground state of Be₂Mg_n^Q (Q = 0, −1; n = 1–11) clusters were performed, which will be absolutely useful for future experiments to identify these clusters.     

[Be3(μ3‐O)3(MeCN)6{Be(MeCN)3}3](I)6 – ein Berylliumkomplex mit Cyclo‐(Be3O3)‐Kern und sein Hydrolyseprodukt [Be(H2O)4](I)2·2MeCN

Single crystals of [Be₃(μ₃‐O)₃(MeCN)₆{Be(MeCN)₃}₃](I)₆·4CH₃CN ( 1 ·4CH₃CN) were obtained in low yield by the reaction of beryllium powder with iodine in acetonitrile suspension, which probably result from traces of beryllium oxide containing the applied beryllium metal. The compound 1 ·4CH₃CN forms moisture sensitive, colourless crystal needles, which were characterized by IR spectroscopy and X‐ray diffraction (Space group Pnma, Z = 4, lattice dimensions at 100(2) K: a = 2317.4(1), b = 2491.4(1), c = 1190.6(1) pm, R₁ = 0.0315). The hexaiodide complex cation 1 ⁶⁺consists of a cyclo‐Be₃O₃ core with slightly distorted chair conformation, stabilized by coordination of two acetonitrile ligands at each of the beryllium atoms and by a {Be(CH₃CN)₃}²⁺ cation at each of the oxygen atoms. This unique coordination behaviour results in coplanar OBe₃ units with short Be–O distances of 155.0 pm and 153.6 pm on average of bond lengths within the cyclo‐Be₃O₃ unit and of the peripheric BeO bonds, respectively. Exposure of compound 1 ·4CH₃CN to moist air leads to small orange crystal plates of [Be(H₂O)₄]I₂·2CH₃CN ( 3 ·2CH₃CN). According to the crystal structure determination (Space group C2/c, Z = 4, lattice dimensions at 100(2) K: a = 1220.7(1), b = 735.0(1), c = 1608.5(1) pm, β = 97.97(1)°, R₁ = 0.0394), all hydrogen atoms of the dication [Be(H₂O)₄]²⁺ are involved to form O–H ··· N and O–H ··· I hydrogen bonds with the acetonitrile molecules and the iodide ions, respectively. Quantum chemical calculations (B3LYP/6‐311+G**) at the model [Be₃(μ₃‐O)₃(HCN)₆{Be(HCN)₃}₃]⁶⁺ show that chair and boat conformation are stable and that the distorted chair conformation is stabilized by packing effects.     

Synthesis and Structure of η4-Enone Complexes of Ruthenium(0)

A variety of [Ru(CO)₂L(η⁴enone)] complexes (L = phosphines, phosphites, and arsines, enone = (E)-4-phenylbut-3-en-2-one) have been synthesized. ¹H-, ¹³C-, and ³¹P-NMR spectra are reported and the X-ray structures of two Ru complexes with L ? Ph₃P(7), Et₃P ( 10 ) and one Fe complex with L ? Ph₃P ( 14 ) are presented. All three compounds crystallize in the same monoclinic space group P2₁/n with a = 10.575(2) Å, b =9.213(2) Å, and c = 27.608(5) Å, β = 100.04(2)°, Z = 4 for 7 , a = 10.276(3) Å, b = 12.935(3) Å, and c = 14.854(2) Å, β = 96.96(2)°, Z = 4 for 10 , and a = 10.492(2) Å, b = 9.232(3) Å, and c = 27.129(3) Å, β = 98.67(2)°, Z = 4 for 14 . The structures of the Ru complexes are compared with the Fe analogues. In the case of M ? Ru and L ? (EtO)₃P, (MeO)₃P, and (i-PrO)₃P ( 9 , 11 , and 13 , respectively) stereoisomers could be detected by ³¹P-NMR at room temperature, wich arise from rotation at the coordinated metal centre.     

Novel Barium Beryllates Ba[Be2N2] and Ba3[Be5O8]: Syntheses,Crystal Structures and Bonding Properties

Ba[Be₂N₂] was prepared as a yellow‐green microcrystalline powder by reaction of Ba₂N with Be₃N₂ under nitrogen atmosphere. The crystal structure Rietfeld refinements (space group I4/mcm, a = 566.46(5) pm, c = 839.42(9) pm, R_int = 4.73 %, R_prof = 9.16 %) reveal the compound to crystallize as an isotype of the nitridoberyllates A[Be₂N₂] (A = Ca, Sr) consisting of planar 4.8² nets of mutually trigonal planar coordinated Be and N species. Averaged magnetic susceptibility values for the anion [(Be₂N₂)^2?] determined from measurements on A[Be₂N₂] with A = Mg, Ca, Ba allow to derive a diamagnetic increment for N^3? χ_dia = (?13±1stat.) · 10^?6emu mol^?1. Colorless Ba₃[Be₅O₈] was first obtained as an oxidation product of Ba[Be₂N₂] in air. The crystal structure was solved and refined from single crystal X‐ray diffaction data (space group Pnma, a = 942.9(1) pm, b = 1163.47(7) pm, c = 742.1(1) pm, R1 = 2.99 %, wR2 = 7.15 %) and contains infinite rods of Be in trigonal planar, tetrahedral and 3 + 1 coordination by O. The crystal structure is discussed in context with other known oxoberyllates. Electronic structure calculations and electron localization function diagrams for both compounds support the classification as nitrido‐ and oxoberyllate, respectively.     

Preparation and crystal structure of members of the solid solution phase Ba5Ru2−xAl1+x−yCuyO11 with x=0.378, y=0.085 and x=0.5, y=0

Single crystals of the new phase Ba₅Ru_2−xAl_1+x−yCu_yO₁₁ (x=0.378, y=0.085) have been grown from a powder mixture of BaCO₃, RuO₂ and CuO in an alumina crucible. The new compound crystallizes isostructurally to Ba₅Ir₂AlO₁₁. The crystal structure was determined by X-ray single-crystal diffraction technique and refined to a composition of Ba₅Ru_1.622(8)Al_1.29(1)Cu_0.085(6)O₁₁ (orthorhombic, Pnma (No. 62), a=18.615(4) Å, b=5.771(1) Å, c=11.098(2) Å, Z=4, R₁=0.048, wR₂=0.075). The composition of the new compound obtained from crystal structure refinement is in good agreement with the result of electron probe microanalysis using wavelength-dispersive X-ray spectroscopy. Octahedra [RuO₆] are connected via faces forming pairs. The central positions of the octahedra pairs are statistically occupied by Ru and Al atoms. These octahedra pairs are interconnected to one-dimensional chains extending along [010] via tetrahedra [Al_1−yCu_yO₄]. Isotypic Ba₅Ru_1.5Al_1.5O₁₁ is a further member of the solid solution with the lattice parameters a=18.6654(5) Å, b=5.7736(1) Å, c=11.0693(3) Å according to Rietveld refinement on a microcrystalline sample.     

Binary Compounds of Boron and Beryllium: A Rich Structural Arena with Space for Predictions

We explore ground‐state structures and stoichiometries of the Be? B system in the static limit, with Be atom concentrations of 20 % or greater, and from P=1 atm up to 320 GPa. At P=1 atm, predictions are offered for several known compounds, the structures of which have not yet been determined experimentally. Specifically, at 1 atm, we predict a structure of R$\bar 3$ m symmetry for the compound Be₂B₃, seen experimentally at high temperatures, which contains interesting BeBBBBe rods; and for the compound BeB₄ we calculate metastability with respect to the elements with a structure similar to MgB₄, which is quickly replaced as the pressure is elevated by a Cmcm structure that features 6‐ and 4‐membered rings in B cages, with Be interstitials. For another high‐temperature compound, Be₂B, we confirm the CaF₂ structure, but find a competitive and actually slightly more stable ground‐state structure of C2/m symmetry that features B₂ pairs. In the case of BeB₂, a material for which the stoichiometry has been the subject of debate, we have a clear prediction of a stable F$\bar 4$ 3m structure at P=1 atm. It has a diamondoid structure that is based on cubic (lower P) or hexagonal (higher P) diamond networks of B, but with Be in the interstices. This Zintl structure is a semiconductor at low and intermediate pressures. At higher pressures, BeB₂ dominates the phase diagram. In general, the Zintl–Klemm concept of effective electron transfer from the more electropositive ion and bond formation among the resulting anions has proven useful in analyzing the structural preferences of many compositions in the Be? B system at P=1 atm and at elevated pressures. An unusual feature of this binary system is that the 1:1 BeB stoichiometry never appears to reach stability in the static limit, although it comes close, as does Be₁₇B₁₂. Also stable at high pressures are stoichiometries BeB₃, BeB₄, and Be₅B₂.     

Synthesis and Characterization of Two Formyl 2‐Tetrazenes

The synthesis of two formyl 2‐tetrazenes, namely, (E)‐1‐formyl‐1,4,4‐trimethyl‐2‐tetrazene ( 2 ) and (E)‐1,4‐diformyl‐1,4‐dimethyl‐2‐tetrazene ( 3 ), by oxidation of (E)‐1,1,4,4‐tetramethyl‐2‐tetrazene ( 1 ) using potassium permanganate in acetone solution is presented. Compound 3 was also synthesized in an improved yield from the oxidation of 1‐formyl‐1‐methylhydrazine ( 4a ) using potassium permanganate in acetone. Both compounds 2 and 3 were characterized by analytical (elemental analysis, GC‐MS) and spectroscopic methods (¹H, ¹³C, and ¹⁵N NMR spectroscopy, and IR and Raman spectroscopy). In addition, the solid‐state structures of the compounds were confirmed by low‐temperature X‐ray analysis. (Compound 2 : triclinic; space group P‐1; a=5.997(1) Å, b=8.714(1) Å, c=13.830(2) Å; α=107.35(1)°, β=90.53(1)°, γ=103.33(1)°; V_UC=668.9(2) ų; Z=4; ρ_calc=1.292 cm^?3. Compound 3 : monoclinic; space group P2₁/c; a=5.840(2) Å, b=7.414(3) Å, c=8.061(2) Å; β=100.75(3)°; V_UC=342(2) ų; Z=2; ρ_calc=1.396 g cm^?3.) The vibrational frequencies of compounds 2 and 3 were calculated using the B3LYP method with a 6‐311+G(d,p) basis set. We also computed the natural bond orbital (NBO) charges using the rMP2/aug‐cc‐pVDZ method and the heats of formation were determined on the basis of their electronic energies. Furthermore, the thermal stabilities of these compounds, as well as their sensitivity towards classical stimuli, were also assessed by differential scanning calorimetry and standard BAM tests, respectively. Lastly, the attempted synthesis of (E)‐1,2,3,4‐tetraformyl‐2‐tetrazene ( 6 ) is also discussed.     

The Structure of cis‐[Chloro(dimethylsulfoxide)bis(1, 10‐phenanthroline)ruthenium(II)]‐tetraphenylborate, [RuCl(DMSO)(1, 10‐phen)2][BPh4]

The complex cis‐[RuCl(DMSO)(phen)₂]BPh₄, where DMSO is dimethylsulfoxide and phen is 1, 10‐phenanthroline, crystallizes in the monoclinic space group P2₁/c with a = 19.505(4), b = 10.045(2), c = 21.199(4) Å, β = 90.137(4)°, V = 4153(2) ų, Z = 4, D_calc = 1.430 g cm^—3. The ruthenium coordination geometry is that of a slightly distorted octahedron with a cis‐RuN₄ClS arrangement of the ligand donor atoms. The Ru—Cl distance is 2.421(1) Å and the Ru—S distance 2.250(2) Å. The four Ru—N distances are 2.057(6), 2.066(4), 2.073(4), and 2.086(4) Å with the Ru—N bond trans to Cl the second shortest and the Ru—N bond trans to S the longest one.     

Wellenmechanische Untersuchungen an der Wasserstoffbrücke zwischen zwei Berylliumatomen

The systems Be₂H⁺ and Be₂H^? have been investigated for different nuclear positions, the H atom being situated between the Be atoms, taking all electrons into account, using the Allgemeines Programmsystem/SCF –MO –LC (LCGO ) Verfahren. For Be₂H⁺ there results a minimum total energy of ?29.3824 a.u. in the linear symmetric configuration with a bond distance of 1.609 Å. The ionization energy was estimated to be 12.37 eV. The formation of Be₂H⁺ can be interpreted as an addition of Be to BeH⁺ with an exotherm heat of reaction of 7.0 kcal/mole. The electron affinity of BeH⁺ (ionization energy of BeH) was estimated to be approximately 7.24 eV. All force constants of Be₂H⁺ and BeH⁺ have been computed. Using SCF results, the Be₂H^? was found to be unstable.     

Design of peptides with α,β-de­hydro residues: a dipeptide with a branched β-carbon de­hydro residue at the (i+1) position,methyl N-(benzyloxycarbonyl)-α,β-dide­hydro­valyl-l-tryptophanate

The structure of the title peptide, C₂₅H₂₇N₃O₅, has been determined and its conformation analysed. Values of the standard peptide torsion angles are ϕ₁ = −44.2 (3)°, ψ₁ = 135.9 (2)°, ϕ₂ = −141.6 (2)° and ψ₂^T = 168.0 (2)°. The crystal structure is stabilized by an intermolecular hydrogen bond, with an N⃛O distance of 2.919 (3) Å, which is formed between screw-axis-related NH and CO groups of de­hydro­valine residues.     

The influence of partial substitution of phosphorus by arsenic in monoclinic CsH2PO4. X-ray single crystal,vibrational and phase transitions in the mixed CsH2(PO4)0.72(AsO4)0.28

Partial substitution of P by As, leading to the solid solution CsH₂(PO₄)_1−x(AsO₄)_x, with x=0.28 (abbreviated as CDAP) has been shown. The structural characteristics of the crystals were analyzed by means of X-ray diffraction, which revealed that the new title compound is nearly isomorphous with the monoclinic phase of CsH₂PO₄ (CDP). The structure was solved from 796 independent reflections with R₁=0.0292 and Rw₂=0.0702, refined with 59 parameters. The following results have been obtained: space group P2₁, a=4.9250(4) Å, b=6.4370(3) Å, c=7.9280(6) Å, β=107.316(3)°, V=239.94(3) Å³, Z=2 and ρ_cal=3.349 g cm⁻³. The hydrogen bonds are clearly distinguished in the electron density maps which display distributions corresponding to order of protons. The shorter bond (2.452(4) Å), links the phosphate–arsenate groups into chains running along the b-axis and the longer bond (2.531(3) Å), crosslinks the chains to form (001) layers. The Raman and infrared spectra of CDAP recorded at room temperature in the frequency ranges 15–1200 cm⁻¹ and 400–4000 cm⁻¹, respectively, confirm the presence of PO³⁻₄ and AsO³⁻₄ groups in the crystal. Differential scanning calorimetry traces show three phase transitions at 333, 449 and 490 K in this material, which are characterized by X-ray powder diffraction at high temperature.     

Two new layered inorganic–organic hybrids: intercalation of 1,3,5-benzenetricarboxylate in lead bisphosphonate

Hydrothermal reactions of N-benzyl-iminobis(methylenephosphonic acid), C₆H₅CH₂N(CH₂PO₃H₂)₂ (H₄L), with lead(II) carbonate in the presence of butane diacid resulted in a new layered lead(II) amino-bisphosphonate, namely, Pb₃L(H₂L)·1.5H₂O 1. When 1,3,5-benzene-tricarboxylic acid (H₃BTC) was used instead of butane diacid, a new layered lead(II) amino-bisphosphonate containing noncoordinated H₃BTC molecules, Pb₃(HL)₂·2(H₃BTC)·2H₂O 2 was isolated. Compound 1 crystallizes in the monoclinic space group P2₁/c with cell dimensions of a=17.6776(14) Å, b=10.0111(8) Å, c=16.6017(13) Å, β=104.134(2)° and Z=4. Compound 2 crystallizes in triclinic space group P-1 with cell parameters of a=4.8797(4) Å, b=9.9736(7) Å, c=24.3631(17) Å, α=97.680(2)°, β=95.0000(10)°, γ=102.4340(10)° and Z=1. Both compounds feature a layered structure and have a same metal/ligand ratio of 3:2. Compound 1 contains two types of ligands with different charges, −2 and −4, respectively. The lead(II) ions are bridged by bisphosphonate ligands, resulting in a 〈100〉 layer. In compound 2, the interconnection of the lead(II) ions by bridging phosphonate groups resulted in a 〈001〉 layer, with the neutral H₃BTC ligand intercalated between two layers, forming hydrogen bonds with lattice water molecules, noncoordinated phosphonate or carboxylate groups. In both compounds, the phenyl groups of the ligands are orientated toward the interlayer space. TGA and IR spectra for both compounds have been also studied.