Kinetics for the gas‐phase reactions of OH radicals with the hydrofluoroethers CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2 at 268–308 K

Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH₂FCF₂OCHF₂(k₁), CHF₂CF₂OCH₂CF₃ (k₂), CF₃CHFCF₂OCH₂CF₃(k₃), and CF₃CHFCF₂OCH₂CF₂CHF₂(k₄) by using a relative rate method. OH radicals were prepared by photolysis of ozone at UV wavelengths (>260 nm) in 100 Torr of a HFE–reference–H₂O–O₃–O₂–He gas mixture in a 1‐m³ temperature‐controlled chamber. By using CH₄, CH₃CCl₃, CHF₂Cl, and CF₃CF₂CF₂OCH₃ as the reference compounds, reaction rate constants of OH radicals of k₁ = (1.68) × 10^?12 exp[(?1710 ± 140)/T], k₂ = (1.36) × 10^?12 exp[(?1470 ± 90)/T], k₃ = (1.67) × 10^?12 exp[(?1560 ± 140)/T], and k₄ = (2.39) × 10^?12 exp[(?1560 ± 110)/T] cm³ molecule^?1 s^?1 were obtained at 268–308 K. The errors reported are ± 2 SD, and represent precision only. We estimate that the potential systematic errors associated with uncertainties in the reference rate constants add a further 10% uncertainty to the values of k₁–k₄. The results are discussed in relation to the predictions of Atkinson's structure–activity relationship model. The dominant tropospheric loss process for the HFEs studied here is considered to be by the reaction with the OH radicals, with atmospheric lifetimes of 11.5, 5.9, 6.7, and 4.7 years calculated for CH₂FCF₂OCHF₂, CHF₂CF₂OCH₂CF₃, CF₃CHFCF₂OCH₂CF₃, and CF₃CHFCF₂OCH₂CF₂CHF₂, respectively, by scaling from the lifetime of CH₃CCl₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 239–245, 2003     

Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution. THF–CH2Cl2 and THF–CH2Cl2/CH3NO2 systems

Cationic polymerization of tetrahydrofuran (THF) in CH₂Cl₂ solvent and in mixed CH₂Cl₂/CH₃NO₂ solvent was initiated with 1,3-dioxolan-2-ylium cations with AsF and SbF anions. Dissociation constants of the polytetrahydrofuranium ion pairs into ions were measured (e.g., K_D = 1.5 × 10^?5M at 25°C and [THF]₀ = 7.0M; CH₂Cl₂ solvent) and were found to be more than 100 times lower than in CH₃NO₂ solvent at the same [THF]₀ and temperature. The rate constants k and k, measured for degrees of dissociation ranging from 0.03 to 0.35 in CH₂Cl₂, were the same within an experimental error of measurements (±15% of the value of k_p). Dependence of k( = k = k) on the dielectric constant was a monotonous function in three different solvents, namely, CCl₄, CH₂Cl₂, and CH₃NO₂, which covered a large range of dielectric constants of the medium (from D = 5 to D = 22) and degrees of dissociation of the macroion pairs, α (from 0.03 to more than 0.70). Thus a decrease in the dielectric constant increases the rate constant k in the whole range of studied polarities of the medium. This result confirms an earlier conclusion that the rate constant of propagation does not depend on the state of aggregation of ions and k = k.     

Das erste Oxocobaltat des Typs A2CoIIO2: K2CoO2 = K4[OCoO2CoO]

The First Oxocobaltate of the Type A₂Co^IIO₂: K₂CoO₂ = K₄[OCoO₂CoO] By “reaction with the cylinder surface” of intimate mixtures of K₂O and CdO (molar ratio 1:1) in closed Co-Cylinders at 450°C during 73 d dark-red single-crystals of K₂CoO₂ were obtained. Structure solution and refinement (four-circle diffractometer-data, MoKα , 1 567 independent I_o(hkl), none was omitted, R = 3.25%, R_w = 2.67%) result in a monoclinic unit cell containing anions [Co₂O₄]^4? of two connected triangles similar to those of Rb₁₀[Co^IO₂]₂[CoO₄]. MAPLE-values and Charge-distributions are given and discussed.     

Conformational preferences of 34 valence electron A2X4 molecules: An ab initio Study of B2F4, B2Cl4, N2O4, and C2O

Ab initio molecular orbital structures and energies of B₂F₄, B₂Cl₄, N₂O₄, and C₂O have been calculated for both perpendicular D_2d and planar D_2h rotamers. The experimental trend toward greater preference for the D_2d forms in going from B₂F₄ to B₂Cl₄ is reproduced. N₂O₄ favors the planar conformation, although the rotation barrier is overestimated at the theoretical levels used. The oxalate dianion is calculated to be more stable in the D_2d conformation; the experimental planar arrangement in the solid may be due to crystal packing forces. The preferences for one conformation over another are small; analysis indicates that different effects may predominate in each case: π stabilization for B₂F₄, hyperconjugation for B₂Cl₄, lone-pair interactions for N₂O₄, and electrostatic repulsions for C₂O.     

Luminescent Nitridophosphates CaP2N4:Eu2+, SrP2N4:Eu2+, BaP2N4:Eu2+, and BaSr2P6N12:Eu2+

Nitridophosphates MP₂N₄:Eu²⁺ (M=Ca, Sr, Ba) and BaSr₂P₆N₁₂:Eu²⁺ have been synthesized at elevated pressures and 1100–1300 °C starting from the corresponding azides and P₃N₅ with EuCl₂ as dopant. Addition of NH₄Cl as mineralizer allowed for the growth of single crystals. This led to the successful structure elucidation of a highly condensed nitridophosphate from single‐crystal X‐ray diffraction data (CaP₂N₄:Eu²⁺ (P6₃, no. 173), a=16.847(2), c=7.8592(16) Å, V=1931.7(6) ų, Z=24, 2033 observed reflections, 176 refined parameters, wR₂=0.096). Upon excitation by UV light, luminescence due to parity‐allowed 4f⁶(⁷F)5d¹→4f⁷(⁸S_7/2) transition was observed in the orange (CaP₂N₄:Eu²⁺, λ_max=575 nm), green (SrP₂N₄:Eu²⁺, λ_max=529 nm), and blue regions of the visible spectrum (BaSr₂P₆N₁₂:Eu²⁺ and BaP₂N₄:Eu²⁺, λ_max=450 and 460 nm, respectively). Thus, the emission wavelength decreases with increasing ionic radius of the alkaline‐earth ions. The corresponding full width at half maximum values (2240–2460 cm^?1) are comparable to those of other known Eu²⁺‐doped (oxo)nitrides emitting in the same region of the visible spectrum. Following recently described quaternary Ba₃P₅N₁₀Br:Eu²⁺, this investigation represents the first report on the luminescence of Eu²⁺‐doped ternary nitridophosphates. Similarly to nitridosilicates and related oxonitrides, Eu²⁺‐doped nitridophosphates may have the potential to be further developed into efficient light‐emitting diode phosphors.     

Ternäre Thallium-Übergangsmetall-Chalkogenide mit ThCr2Si2-Struktur

The existence of ternary chalcogenides of general composition TlT ₂ X ₂ (T=Fe,Co,Ni,X=S;T=Fe,Co,Ni,Cu,X=Se) crystallizing in the ThCr₂Si₂-structure type has been established. The crystal structure of TlCo₂S₂ was refined from single crystal diffractometer data. The dimensions of the tetragonal unit cells are: TlFe₂S₂;a=3.755 (1),c=13.35 (1) Å; TlCo₂S₂:a= =3.7410 (5),c=12.956(5) Å; TlNi₂S₂:a=3.792 (1),c=12.77 (1) Å; TlFe₂Se₂:a=3.890 (1),c=14.00(1) Å; TlCo₂Se₂:a=3.847 (1),c=13.54 (1) Å; TlNi₂Se₂:a=3.866 (1),c=13.41 (1) Å; TlCu₂Se₂:a=3.852 (1),c=14.01 (1) Å. These phases are the first chalcogenides found to crystallize in the ThCr₂Si₂-structure type. Unlike the already known representatives of this structure type they show a pronounced partial ionic character. Interatomic distances as well as the relations to the alkali thiometallates of Co and Mn are discussed.     

Kristallstruktur von Sulfamid,SO2(NH2)2

X-ray crystal structure analyses of sulfamide were carried out at 293 K and at 100 K:M=96.10, orthorhombic, Fdd2,Z=8,F(000)=400, Mo K, =0.71069 Å (graphite monochromator). A) 293 K:a=9.127 (1) Å,b=16.857 (5) Å,c=4.579 (1) Å,V=704.50 ų,d _x =1.812 Mgm^–3, =0.648 mm^–1,R=1.77%,R _w =1.94% (384 reflections, 33 parameters). B) 100K:a=9.059 (1) Å,b=16.780 (8) Å,c=4.517 (1) Å,V=686.63 ų,d _x =1.859 Mgm^–3, =0.665 mm^–1,R=1.78%,R _w =1.95% (404 reflections, 33 parameters). The sulfamide molecule shows at 293 K S-O and S-N distances of 1.429 (1) Å and 1.620 (1) Å, respectively, which are in agreement with IR data. Hydrogen positions could be determined from differenceFourier syntheses. Strong weakening of some intense low order reflections by extinction was observed, their anisotropy depends on the crystal and on temperature.

     

(C2H10N2)[BPO4F2] — Structural Relations between [BPO4F2]2— and [Si2O6]4—

(C₂H₁₀N₂)[BPO₄F₂] — Strukturbeziehungen zwischen [BPO₄F₂]^2— und [Si₂O₆]^4— Colourless crystals of (C₂H₁₀N₂)[BPO₄F₂] were prepared from mixture of ethylendiamine, H₃BO₃, BF₃ · C₂H₅NH₂, H₃PO₄ and HCl under mild hydrothermal conditions (220 °C). The crystal structure was determined by single crystal methods (triclinic, P1¯ (no. 2), a = 451.85(5) pm, b = 710.20(8) pm, c = 1210.2(2) pm, α = 86.08(1)°, β = 88.52(2)°, γ = 71.74(1)°, Z = 2) and contains infinite tetrahedral zweier‐single‐chains {[BPO₄F₂]^2—} which are isoelectronic (48e^—) with the polyanions {[Si₂O₆]^4—} of the pyroxene family.     

Die Kristallstruktur von Trikobalt(II)-dihydroxidsulfat-dihydrat,Co3(OH)2(SO4)2 · 2 H2O

Tricobalt (II)-dihydroxidesulfate-dihydrate, Co₃(OH)₂(SO₄)₂ · 2H₂O, is orthorhombic: a = 7.21, b = 9.77, c = 12.86 Å, V = 905.9 ų, space group D-Pbcm with four formula units per cell. The atomic positions have been determined by threedimensional Patterson and Fourier synthesis and full-matrix least-squares refinement of single crystal X-ray diffraction data. The structure shows infinite chains [001] of Co? O octahedra sharing one edge with each other. These chains are linked together by alternating SO₄ tetrahedra and additional Co? O octahedra, thus giving rise to a three-dimensional network of polyhedra. There is no similarity to the well known layer structures of most hydroxide salts of divalent metals. The SO₄ tetrahedra are regular while the Co? O octahedra show considerable distortion. The water molecule is coordinated to one Co atom and bonded to sulfate oxygen by two weak hydrogen bridges.     

A copper–polyol complex: [Na2(C2H6O2)6][Cu(C2H4O2)2]

The ionic title complex, bis(μ‐ethylene glycol)‐κ³O,O′:O′;κ³O:O,O′‐bis[(ethylene glycol‐κ²O,O′)(ethylene glycol‐κO)sodium] bis(ethylene glycolato‐κ²O,O′)copper(II), [Na₂(C₂H₆O₂)₆][Cu(C₂H₄O₂)₂], was obtained from a basic solution of CuCl₂ in ethylene glycol and consists of discrete ions interconnected by O—H...O hydrogen bonds. This is the first example of a disodium–ethylene glycol complex cation cluster. The cation lies about an inversion center and the Cu^II atom of the anion lies on another independent inversion center.     

Syntheses and Crystal Structures of PbSbO2Br,PbSbO2I,and PbBiO2Br

Transparent single crystals of PbSbO₂Br (green), PbSbO₂I, and PbBiO₂Br (yellow) were obtained by solid state reactions of stoichiometric amounts of PbO, Pn₂O₃ (Pn = Sb, Bi) and PnX₃ (X = Br, I). The crystal structures were determined from single‐crystal X‐ray data. The title compounds crystallize tetragonally in the space group I4/mmm (No. 139): Lattice constants and refinement values are: PbSbO₂Br: a = 3.9463(3), c = 12.849(1) Å, V = 200.10(3) Å³, and Z = 2, R₁ = 0.0236, and wR₂ = 0.0513. PbSbO₂I: a = 4.0074(3), c = 13.627(2) Å, V = 218.84(3) Å³, and Z = 2, R₁ = 0.0244, and wR₂ = 0.0538. PbBiO₂Br: a = 3.9818(2), c = 12.766(2) Å, V = 202.39(4) Å³, and Z = 2, R₁ = 0.0276, and wR₂ = 0.0715. The compounds are isotypic and crystallize in the anti‐ThCr₂Si₂ structure type with lead and Pn statistically disordered on one common position. In case of Pn = Sb a slight separation of the positions of the cations becomes obvious. Optical bandgaps were determined by UV/Vis spectroscopy. They are 2.67 eV (PbSbO₂Br), 2.48 eV (PbSbO₂I), and 2.47 eV (PbBiO₂Br).     

Dipotassium Sodium Diantimonidoindate,K2Na[InSb2], a compound with the polyanion [In2Sb2Sb4/2]6−

The novel compound K₂Na[InSb₂] was synthesized from the elements at 900 K in sealed niobium ampoules. The compound forms plate-like crystals with silver metallic luster, which are very unstable in air and moisture. The crystal structure of K₂NaInSb₂ has been determined using single-crystal X-ray diffraction methods (space group Cmca (No. 64); a = 14.032(2), b = 16.399(3), c = 7.009(1) Å; Z = 8; Pearson symbol oC48). The structure contains pairs of edge-sharing InSb₄ tetrahedra which are linked to four other pairs via common vertices and form a two-dimensional [In₂Sb₂Sb_4/2]^6? anionic partial structure. The resulting pairs of tetrahedral holes are filled by Na⁺ cations. These [In₂Sb₂Sb_4/2]^6? layers are stacked along the b-axis and are interconnected by K⁺ cations. The whole structure can be considered as an ordered derivative of the KMnP structure (PbFCl type).     

Phosphaniminato-Komplexe von Bor. Synthese und Kristallstrukturen von [BBr2(NPMe3)]2, [B2Br3(NPiPr3)2]Br, [B2(NPEt3)4]Br2, [B2Br2(NPPh3)3]BBr4 und [{B2(NMe2)2}2(NPEt3)2]Cl2

Phosphoraneiminato Complexes of Boron. Syntheses and Crystal Structures of [BBr₂(NPMe₃)]₂, [B₂Br₃(NPⁱPr₃)₂]Br, [B₂(NPEt₃)₄]Br₂, [B₂Br₂(NPPh₃)₃]BBr₄ and [{B₂(NMe₂)₂}₂(NPEt₃)₂]Cl The bromoderivatives of the title compounds are prepared from the corresponding silylated phosphoraneimines Me₃SiNPR₃ and boron tribromide. The boron subcompound [{B₂(NMe₂)₂}₂(NPEt₃)₂]Cl₂ derives from Me₃SiNPEt₃ and B₂Cl₂(NMe₂)₂. All complexes are characterized by NMR and IR spectroscopy as well as by crystal structure determinations. [BBr₂(NPMe₃)]₂ (1): Space group P2₁/n, Z = 2, R = 0.031. Lattice dimensions at ?50°C: a = 723.8, b = 894.2, c = 1305.4 pm, β = 92.35°. 1 forms centrosymmetric molecules in which the boron atoms are linked via μ₂-N bridges of the NPMe₃^? groups of from B₂N₂ four-membered rings with B? N distances of 149.9 and 150.9 pm. B₂Br₃(NPⁱPr₃)₂]Br (2): Space group P2₁, Z = 2, R = 0.059. Lattice dimensions at ?80°C: a = 817.6, b = 2198.7, c = 851.5 pm, β = 115.09°. In the cations of 2 the boron atoms are lined via the μ₂-N atoms of the NPⁱPr₃^? groups to form planar, asymmetric B₂N₂ four-membered rings with B? N distances of 143 and 156 pm. [B₂(NPEt₃)₄[Br₂·4CH₂Cl₂ (3): Space group C2/c, Z = 4, R = 0.042. Lattice dimensions at ?50°C: a = 1946.1, b = 1180.3, c = 2311.3 pm, β = 101.02°. The structure contains centrosymmetric dications in which both the boron atoms are lined by the N atoms of two of the NPEt₃^? groups to form a B₂N₂ four-membered ring with B? N distances of 149.6 pm. The remaining two NPEt₃^? groups are terminally bonded with very short B? N distances of 133.5 pm. B₂Br₂(NPPh₃)₃]BBr₄ (4): Space group P1 , Z = 2, R = 0.065. Lattice dimension at ?50°C: a = 1025.7, b = 1496.1, c = 1807.0 pm, α = 85.09°, β = 82.90°, γ = 82.72°. In the cation the boron atoms are lined via the μ₂-N atoms of two of the NPPh₃^? groups to form a nearly planer B₂N₂ four-membered ring with B? N distances of 149.3-153.1 pm. The third NPPh₃³ group is terminally connected with teh sp² hybridized boron atom and with a B? N distance of 134.1 pm along with an almost linear BNP bond angle of 173.6°. [{B₂(NMe₂)₂}₂(NPEt₂)₂]Cl₂ · 3CH₂Cl₂ (5): Space group C2/c, Z = 4, R = 0.098. Lattice dimensions at ?70°C: a = 1557.9, b = 1294.7, c = 2122.9 pm, β = 96.08°. The structure of 4 contains centrosymmetric dications in which two by two B-B dumb-bells are linked via the μ₂-N atoms of the two NEPt₃^? groups to form B₄N₂ six-membered rings with B? N distances of 150 and 156 pm and B-B distances of 173 pm. The B? N distances of the terminally bonded NMe₂^? groups correspond to 138 pm double bonds.     

Na2Ba[Na2Sn2S7]: Structural Tolerance Factor-Guided NLO Performance Improvement

The strong mutual coupling of and even the opposite change in the key parameters, such as the band gap (E_g) and second-order harmonic generation (SHG), leads to the extreme scarcity in high-performance IR nonlinear optical (NLO) chalcogenides. Herein, we report 8 new sulfides, Na₂Ba[(Ag_xNa_1−x)₂Sn₂S₇] ( 1 , x=0; 1 series , x=0.1–0.6; Na₂Ba[(Li_0.58Na_0.42)₂Sn₂S₇], 1-0.6Li ); Na₂Sr[Cu₂Sn₂S₇] ( 2 ); and Na₂Ba[Cu₂Sn₂S₇] ( 3 ). We use the structural tolerance factor ( ) to connect the chemical composition, crystal structure, and NLO properties. Guided by these correlations, a better balance between E_g and SHG is realized in 1 , which exhibits a large E_g of 3.42 eV and excellent NLO properties (SHG: 1.5×AGS; laser-induced damage threshold: 12×AGS), representing the best performance among the known Hg- or As-free sulfides to date.     

Kristallstrukturen aus CaBe2Ge2‐ und CeMg2Si2‐analogen Blöcken: Die Phosphide LnPt2P2−x (Ln: La,Sm)

Crystal Structures of CaBe₂Ge₂ and CeMg₂Si₂ analogous Units: The Phosphides LnPt₂P_2?x (Ln: La, Sm) Single crystals of LaPt₂P_1.44 (a = 4.174(1), c = 19.212(5) Å) were grown by reaction of vaporous phosphorus with LaPt₂ at 1050 °C during two weeks, whereas SmPt₂P_1.50 (a = 4.131(1), c = 19.086(4) Å) was synthesized by heating mixtures of the elements at 900 and 1100 °C (60 h) and annealing at 1050 °C (300 h). Both phosphides were investigated by single crystal X‐ray methods. Their crystal structures (I4/mmm; Z = 4) consist of CaBe₂Ge₂ and CeMg₂Si₂ analogous units alternating with each other along [001]. The positions of the P1 atoms are occupied incompletely causing the deviation to the 1:2:2 stoichiometry. Another compounds LnPt₂P_2?x were studied by X‐ray powder diffraction resulting in the following lattice constants: a = 4.150(1), c = 19.132(5) Å for CePt₂P_2–x, a = 4.137(1), c = 19.085(4) Å for PrPt₂P_2?x, and a = 4.127(1), c = 19.040(2) Å for NdPt₂P_2?x.     

Gitterkonstanten und Strukturen der Verbindungen DyHg,HoHg, ErHg; DyHg2, HoHg2, ErHg2; DyHg3, HoHg3 und ErHg3

Zusammenfassung Durch direkte Reaktion der metallischen Komponenten Dy, Ho oder Er mit Hg werden die PhasenSEHg,SEHg₂ undSEHg₃ (SE-Dy, Ho, Er) hergestellt. Ihre Gitterkonstanten und Kristallstrukturen [SEHg: CsCl(B 2)-Typ;SEHg₂: AlB₂(C 32)-Typ;SEHg₃: Mg₃Cd(DO₁₉)-Typ] werden bestimmt.

---

A direct reaction between the metallic components Dy, Ho or Er with Hg yields the phasesREHg,REHg₂ andREHg₃ (RE=Dy, Ho, Er). The lattice spacings and crystal structures [REHg: CsCl(B 2)-type;REHg₂: AlB₂(C 32)-type;REHg₃: Mg₃Cd(DO₁₉)-type] have been established.

     

Three Modifications of [Pr2(ClO4)2(H2I2O10)]·8 H2O — A Theme with Variations

From solutions containing praseodymium perchlorate and periodic acid, three different modifications of [Pr₂(ClO₄)₂(H₂I₂O₁₀)] · 8 H₂O could be obtained. All of them crystallize in the monoclinic system, space group P2₁/c (α: a = 1091.47(6), b = 728.24(4), c = 1388.84(8) pm, β = 101.420(3)°; β: a = 1169.93(3), b = 728.72(2), c = 1384.50(4) pm, β = 112.303(2)°; γ: a = 1209.56(4), b = 712.53(2), c = 1361.64(5) pm, β = 115.691(1)°). The structures contain Pr³⁺ cations which are coordinated by [H₂I₂O₁₀]^4— anions yielding two‐dimensional networks. These networks are separated by ClO₄^— anions yielding a layered structure.     

Synthesis and crystal structure of [V_2(μ-S_2)_2(S_2CNEt_2)_4]·2CH_3Cl

[V_2(μ-S_2)_2(S_2CNEt_2)_4].2CH_3Cl was synthesized by the reaction of NaS_2CNEt_2,Li_2S andVOCl_3 at room temperature.Crystal data:M=1061.3,space group Pbca,with the orthorhombicparameters:a=20.123(3),b=20.485(4),c=10.911(3),V=4497.7,Z=4,D_c=1.57g/cm~3,Mo Kσradiation(λ=0.71069()?),μ=13.2 cm~(-1),F(000)=2168.Final R=0.041 and R_w=0.047 for 2288 ob-served reflections with I>3σ(1).The coordination sphere of each V atom in title compound is a dis-torted tetragonal prism composed of two bidentate dithiocarbamate and two S_(2~((2-)) ligands.The V—Vdistance is 2.890 while the V—S distances fall in the range of 2.422—2.505.     

Die Kristallstruktur von HfBe2, HfBe13 und HfBeSi; Teilsysteme: MeBe2-MeB2-MeSi2 (Me=Zr,Hf)

Zusammenfassung Legierungen im Zweistoff Hf-Be sowie auf den Schnitten: HfBe₂-HfSi₂, ZrBe₂-ZrSi₂, ZrBe₂-ZrB₂, HfBe₂-HfB₂, ZrSi₂-ZrB₂ und HfSi₂-HfB₂ wurden an Hand druckgesinterter Proben röntgenographisch untersucht. HfBe₂ kristallisiert im AlB₂-Typ mit:a=3,788,c=3,168 Å, HfBe₁₃ ist mit NaZn₁₃ isotyp:a=10,010 Å. Auf dem Schnitt HfBe₂-HfSi₂ liegt eine ternäre Phase HfBeSi, die mit HfSi₂ bzw. HfSi und HfBe₂ im Gleichgewicht steht. HfSiBe besitzt eine aufgefüllte NiAs-Struktur mit:a=3,693 undc=7,135 Å. HfBe₂ vermag kein Silicium bzw. HfSi₂ zu lösen. Die Kristallarten ZrSiBe, ZrBe₂ und ZrBe₁₃ (a=10,044 Å) werden bestätigt. ZrSiBe tritt in einem homogenen Bereich auf:a=3,722,c=7,232 Å an der siliciumreichen unda=3,718,c=7,217 Å an der berylliumreichen Homogenitätsgrenze. ZrB₂ und HfB₂ nehmen bei 1400° rd. 12 bzw. 15 Mol% der entsprechenden Diberyllide auf, während umgekehrt diese kein Diborid lösen. In dem Schnitt: MeSi₂-MeB₂ (Me=Hf, Zr) lassen sich keine Phasen vom Typ MeSiB nachweisen.Mit 2 Abbildungen