Synthese und Kristallstruktur von Cs3AuO2

Synthesis and Crystal Structure of Cs₃AuO₂ Bright orange single crystals of Cs₃AuO₂, sensitive to moisture and atmosphere, are obtained by reacting CsAu with a 1 : 1 molar mixture of Cs₂O and CsO₂ (CsAu : Cs₂O : CsO₂ = 3 : 2 : 2) in sealed silver crucibles under argon atmosphere at 380 °C for a period of 6 days. The crystal structure (Pearsoncode mP72, P2₁/n, a = 1019.6(3), b = 1984.3(7), c = 1028.5(4) pm, β = 93.96(1)°, Z = 12, 2562 reflections mit I_o > 2σ(I), R₁ = 0.0662, wR₂ = 0.1660) is characterized by the presence of dumb‐bell‐shaped [O–Au–O]‐moieties (d(Au–O) = 200,8(2) pm), a common feature of oxoaurates(I).     

A New Type of Divalent Europium Compound MEuPO4 (M = K,Rb, Cs), its Synthesis,Crystal Structure,and Properties

Phosphates MEuPO₄ with M = K, Rb, and Cs were synthesized by the reduction of EuPO₄ with alkali metal vapour under 1 Pa of argon pressure at 260–530°C in sealed tantalum or niobium lined glass tubes. All the compounds belong to the β-K₂SO₄ orthorhombic structure with a = 7.359(3), b = 9.630(4), c = 5.569(2) Å, V = 394.7(2) ų for KEuPO₄, a = 7.462(3), b = 9.797(3), c = 5.649(2) Å, V = 413.0(2) ų for RbEuPO₄ and a = 7.889(2), b = 10.099(2), c = 5.820(4) Å, V = 463.6(2) ų for CsEuPO₄. Samples are stable and not hygroscopic in air at room temperature but hydrolyse to Eu₅(PO₄)₃OH, hexagonal, a = 9.764(2), c = 7.262(2) Å, on heating in water and decompose to Eu₃(PO₄)₂, hexagonal, a = 5.393(1), c = 19.838(3) Å, under argon at ca. 600°C. All the five compounds are paramagnetic.     

Darstellung und Kristallstruktur von CsTe4

Preparation and Crystal Structure of CsTe₄ CsTe₄ results from a melting reaction at 570°C in sealed quartztubes. The starting materials Cs and Te in the molar ratio 1:4 are produced in a first step by controlled decomposition of the CsN₃ from mixtures of CsN₃ and Te (1:4) at 350°C. CsTe₄ is monoclinic, space group P2₁/c, with a = 7.857(1) Å, b = 7.286(1) Å, c = 14.155(2) Å, β = 93.83(1)°, and Z = 4. The tellurium atoms form a two-dimensional puckered layer built of from pseudo-trigonal-bipyramidal, T-shaped units Te₄^?. The central tellurium atom of this unit may be considered as a pseudo iodine. The compound is compared with other tellurides MTe_n having some like that unexpected principles of connection.     

Neue Oxocuprate (I). Über Cs3Cu5O4, Rb2KCu5O4, RbK2Cu5O4 und K3Cu5O4

New Oxocuprates(I). On Cs₃Cu₅O₄, Rb₂KCu₅O₄, RbK₂Cu₅O₄ and K₃Cu₅O₄ Cs₃Cu₅O₄ light yellow, powder as well as single crystals [a = 10.313(9), b = 7.630(1), c = 14.750(4) Å, β = 106.48(6)°], Rb₂KCu₅O₄ [a = 9.724(2), b = 7.443(0), c = 14.246(2) Å, β = 106.78(8)°], RbK₂Cu₅O₄ [a = 9.561(1), b = 7.411(0), c = 14.111(1) Å, β = 106.76(7)°] and K₃Cu₅O₄ [a = 9.422(1), b = 7.364(1), c = 13.995(2) Å, β = 107.00(2)°] are new prepared. The colour of the powders becomes lighter according to the sequence showed above. K₃Cu₅O₄ shows pale yellow. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Syntheses,Structures, and Properties of New Quaternary Gold-Chalcogenides: K2Au2Ge2S6, K2Au2Sn2Se6, and Cs2Au2SnS4

The new compounds K₂Au₂Ge₂S₆ ( 1 ), K₂Au₂Sn₂Se₆ ( 2 ), and Cs₂Au₂SnS₄ ( 3 ) have been synthesized through direct reaction of the elements with a molten polyalkalithiogermanate(stannate) flux at 650, 550, and 400 °C, respectively. Their crystal structures have been determined by single crystal X-ray diffraction techniques. 1 crystallizes in the monoclinic space group P2₁/n with a = 10.633(2) Å, b = 11.127(2) Å, c = 11.303(2) Å, β = 115,37(3)°, V = 1208,2(3) ų and Z = 4, final R(Rw) = 0.045(0.106). 2 crystallizes in the tetragonal space group P4/mcc with a = 8.251(1) Å, c = 19.961(4) Å, V = 1358,9(4) ų and Z = 4, final R(Rw) = 0.040(0.076). 3 crystallizes in the orthorhombic space group Fddd with a = 6.143(1) Å, b = 14.296(3) Å, c = 24.578(5) Å, V = 2158.4(7) ų and Z = 4, final R(Rw) = 0.039(0.095). The structures of 1 , 2 , and 3 consist of infinite, one-dimensional anionic chains containing X₂Q₆^4– units linked by Au⁺ ions and charge balancing K⁺/Cs⁺ ions situated between the chains. All compounds were investigated with differential thermal analysis, FT-IR, and solid state UV/VIS diffuse reflectance spectroscopy.     

Synthese,Struktur und Reaktionen von Vanadiumsäureestern VO(OR)3: Umesterung und Reaktion mit Oxalsäure

Synthesis, Structure, and Reactions of Vanadium Acid Esters VO(OR)₃: Transesterification and Reaction with Oxalic Acid The reaction of tert.‐Butyl Vanadate VO(O‐tert.Bu)₃ ( 1 ) with H₂C₂O₄ in the primary alcohols ethanol and propanol results in the formation of (ROH)(RO)₂OV^V(C₂O₄)V^VO(OR)₂(HOR) (with R = C₂H₅ 2 and R = C₃H₇ 3 ). Compounds 2 and 3 are the first structurally characterized neutral, binuclear oxo‐oxalato‐complexes with pentavalent vanadium. The two vanadium atoms are connected by a bisbidentate oxalate group. The {VO₆} coordination at each vanadium site is completed by a terminal oxo group, an alcohol ligand and two alcoxide groups. The binuclear molecules are connected to chains by hydrogen bonding. In the case of 2 a reversible isomorphic phase transition in the temperature range of –90 °C to –130 °C is observed. From methanolic solution the polymeric Methyl Vanadate [VO(OMe)₃] ( 4 ) was obtained by transesterification. A report on the crystal structures of 1 , 2 and 3 as well as a redetermination of the structure of 4 is given. Crystal data: 1, orthorhombic, Cmc2₁, a = 16.61(2) Å, b = 9.274(6) Å, c = 10.784(7) Å, V = 1662(2) ų, Z = 4, d_c = 1.144 gcm^–1; 2 (–90 ° C) , monoclinic, I2/a, a = 33.502(4) Å, b = 7.193(1) Å, c = 15.903(2) Å und β = 143.060(3)°, V = 2303(1) ų, Z = 4, d_c = 1.425 gcm^–1; 2 (–130 ° C) , monoclinic, I2/a, a = 33.274(4) Å, b = 7.161(1) Å, c = 47.554(5) Å, β = 142.798(2)°, V = 6851(1) ų, Z = 12, d_c = 1.438 gcm^–1; 3 , triklinic, P1, a = 9.017(5) Å, b = 9.754(5) Å, c = 16.359(9) Å, α = 94.87(2)°, β = 93.34(2)°, γ = 90.42(2)°, V = 1431(1) ų, Z = 2, d_c = 1.340 gcm^–1; 4 , triklinic, P1, a = 8.443(2) Å, b = 8.545(2) Å, c = 9.665(2) Å, α = 103.202(5)°, β = 96.476(5)°, γ = 112.730(4)°, V = 610.2(2)ų, Z = 4, d_c = 1.742 gcm^–1.     

Cs2Ba(O3)4 · 2 NH3, das erste ionische Erdalkaliozonid

Cs₂Ba(O₃)₄ · 2 NH₃, the First Ionic Alkaline Earth Metal Ozonide Cs₂Ba(O₃)₄ · 2 NH₃ is the first ionic ozonide containing an alkaline earth metal cation. Its synthesis has been achieved via partial cation exchange of CsO₃ dissolved in liquid ammonia. According to a single crystal X‐ray structure determination (Pnnm; a = 6.312(2) Å, b = 12.975(3) Å, c = 8.045(2) Å; Z = 2; R₁ = 4.6%; 848 independent reflections) ozonide anions, cesium cations and ammonia molecules form a CsCl‐type arrangement, where Cs⁺ and NH₃ occupy one half of the cation sites, each. Ba²⁺ is coordinated by four ozonide groups and two ammonia molecules. Because of a short hydrogen bond to one of the terminal oxygen atoms, the respective O–O‐distance in the ozonide ion is longer than the other. The shortest intermolecular O–O‐distance ever observed in ionic ozonides has been found in this compound, which can be taken as a first clue for the radical ozonide anion to dimerize like the isoelectronic SO₂^– does.     

Drei neue Selenoborato-closo-dodekaborate: Synthesen und Kristallstrukturen von Rb8[B12(BSe3)6], Rb4Hg2[B12(BSe3)6] und Cs4Hg2[B12(BSe3)6]

Three Novel Selenoborato- closo -dodecaborates: Syntheses and Crystal Structures of Rb₈[B₁₂(BSe₃)₆], Rb₄Hg₂[B₁₂(BSe₃)₆], and Cs₄Hg₂[B₁₂(BSe₃)₆] The three selenoborates Rb₈[B₁₂(BSe₃)₆] (P1, a = 10.512(5) Å, b = 10.450(3) Å, c = 10.946(4) Å, α = 104.53(3)°, β = 91.16(3)°, γ = 109.11(3)°, Z = 1), Cs₄Hg₂[B₁₂(BSe₃)₆] (P1, a = 9.860(2) Å, b = 10.740(2) Å, c = 11.078(2) Å, α = 99.94(3)°, β = 90.81(3)°, γ = 115.97(3)°, Z = 1), and Rb₄Hg₂[B₁₂(BSe₃)₆] (P1, a = 9.593(2) Å, b = 10.458(2) Å, c = 11.131(2) Å, α = 99.25(3)°, β = 91.16(3)°, γ = 116.30(3)°, Z = 1) were prepared from the metal selenides, amorphous boron and selenium by solid state reactions at 700 °C. These new chalcogenoborates contain B₁₂ icosahedra completely saturated with six trigonal-planar BSe₃ entities functioning as bidentate ligands to form a persubstituted closo-dodecaborate anion. The two isotypic compounds Rb₄Hg₂[B₁₂(BSe₃)₆] and Cs₄Hg₂[B₁₂(BSe₃)₆] are the first selenoborate structures containing a transition metal which are characterized by single crystal diffraction.     

Cs4BiAs3Se7: A Novel Bismuth‐Selenoarsenate with Infinite [BiAs3Se7]4– Chains Containing Two Different Anions, [AsSe3]3– and trans‐[As2Se4]4–

A new phase has been prepared by methanolothermal reaction of Cs₂CO₃, BiCl₃ and Li₃AsSe₃ at 130 °C for 36 hours. Cs₄BiAs₃Se₇ ( I ) reveals the first Bi‐selenoarsenate polyanionic chain [Bi(As₂Se₄)(AsSe₃)]^4–, consisting of Bi³⁺ ions in a distorted octahedral environment of [AsSe₃]^3– and trans‐[As₂Se₄]^4– units. The latter anion consists of a central “As₂⁴⁺” dumb‐bell whereby two Se atoms are attached to each of the As atoms. Structural Data: Space Group P2₁/n, a = 13.404(4) Å, b = 23.745(8) Å, c = 13.880(4) Å, β = 99.324(6)°, Z = 8.     

Darstellung,Kristallstruktur und Eigenschaften von Cäsiumozonid

Synthesis, Crystal Structure and Properties of Cesium Ozonide By reaction between CsO₂ and mixtures of O₂ and O₃ in the temperature range from 25°C to ?70°C and subsequent extraction with liquid ammonia pure CsO₃ was obtained in grammeamounts. By X-ray powder and thermal techniques a reversible, structural phase transition was detected at +8°C, and decomposition into CsO₂ and O₂ at +53°C. The low-temperature form (T? CsO₃) is isostructural to RbO₃ (P2₁/c; a = 675.1(2), c = 901.5(3) pm, β = 120.74(3)°l Z = 4), the crystal structure of H? CsO₃, which shows orientational disorder with respect to the ozonide ion, corresponds to the CsCl-type of structure (a = 436.06(3) pm). Using the geometry as determined for KO₃ and RbO₃, and the vibrational frequencies of different isotopomeres, the force constants of O₃^? have been redetermined.     

Die Kristall- und Molekülstruktur von Dicäsium- μ-Oxodekafluorodiarsenat

Crystal and Molecular Structure of Dicaesium-μ-Oxodecafluorodiarsenate, Cs₂(As₂F₁₀O) The crystal structure of Cs₂(As₂F₁₀O) has been determined from three-dimensional data. The compound crystallizes in the monoclinic space group P2₁/m, the lattice constants being a = 9.175(4), b = 10.690(5), c = 5.619(3)(Å); β = 105,50(5)°. The anion (As₂F₁₀O)^2– with the point symmetry C_s contains a As? O? As-bridge, whose partial π-bonding is to be discussed. The bond lengths and angles are: As? O: 1.77(2) and 1.68(2) Å, resp., As? O? As: 139(1)°; As…As: 3.225(4) Å, the numbers in parantheses being the standard deviation of the last figure.     

New Heptafluorozirconates and ‐hafnates AIBIIZr(Hf)F7 (AI = Rb,Tl; BII = Ca,Cd) – Synthesis,Structures, and Structural Relationships

Four new ABZrF₇ heptafluorozirconates (A = Rb, Tl; B = Ca, Cd) and their homologous heptafluorohafnates, all colorless, orthorhombic Cmcm (n^o63), Z = 4, have been synthesized by heating stoichiometric mixtures of RbF or TlF, CaF₂ or CdF₂ and ZrF₄ (HfF₄) in sealed platinum tubes at temperature ranging from 550 °C (Tl) to 600 °C (Rb). The crystal structures of both RbCdZrF₇ and TlCdZrF₇ have been solved from single‐crystal X‐rays diffraction data. Rietveld refinements were performed from X‐rays powder patterns for RbCaZrF₇ and TlCaZrF₇. In this series of heptafluorides, both B²⁺ and Zr⁴⁺ cations exhibit a pentagonal bipyramidal 7‐coordination. Their structural relationships with other heptafluorozirconates A^IB^IIZrF₇ as well as β‐KYb₂F₇ are discussed. RbCaZrF₇: a = 6.863(1) Å, b = 11.130(1) Å, c = 8.485(1) Å; TlCaZrF₇: a = 6.868(1) Å, b = 11.165(1) Å, c = 8.486(1) Å; RbCdZrF₇: a = 6.780(1) Å, b = 11.054(4) Å, c = 8.420(4) Å; TlCdZrF₇: a = 6.784(3) Å, b = 11.099(2) Å, c = 8.424(9) Å.     

Ein Oxostannat neuen Strukturtyps: Cs4[SnO4]

An Oxostannate of a New Structure Type: Cs₄[SnO₄] In order to prepare Cs₃LiSnO₄ by heating of a well ground mixture of the binary oxides [CsO_0.67, Li₂O, SnO₂; Cs:Li:Sn = 3.3:1.0:1.0; 450°C; 28 d; Ni-tube] colourless, monoclinic single crystals of Cs₄[SnO₄] have been yielded for the first time: space group P2₁/c with a = 1180.8 pm. b = 728.2 pm, c = 1166,7 pm, β = 111.79°, Z = 4. The crystal structure was solved by fourcycle-diffractometer data [Siemens AED2, 2299 from 2708 I₀(hkl), R = 7.0%, R_w = 5.6%], parameters see text. Characteristic for the complicated structure are “isolated” [SnO₄]^4? tetrahedra. Mean Fictive Ionic Radii, MEFIR, Effective Coordination Numbers, ECoN and the Madelung Part of Lattice Energy, MAPLE, have been calculated.     

Caesiumchloropalladat(II)‐hydrate – zwei neue Verbindungen mit kondensierten [Pd2Cl6]‐Baugruppen

Caesiumchloropalladate(II)‐hydrates – Two New Compounds with Condensed [Pd₂Cl₆] Groups We were able to synthesize two caesiumchloropalladate(II)‐hydrates in the CsCl/PdCl₂/H₂O system by hydrothermal methods. Both compounds show combination of monomeric and dimeric Pd–Cl groups. We characterized the crystal structures by single‐crystal X‐ray diffraction. Cs₆Pd₅Cl₁₆ · 2 H₂O ( I ) crystallizes triclinic in space group type P1 (Nr. 2) with a = 8.972(1) Å, b = 11.359(1) Å, c = 18.168(1) Å, α = 83.61(1)°, β = 76.98(1)°, γ = 76.39(1)° and Z = 2, Cs₁₂Pd₉Cl₃₀ · 2 H₂O ( II ) monoclinic, space group type C2/m (No. 12) with a = 19.952(1) Å, b = 14.428(1) Å, c = 14.411(1) Å, β = 125.29(1)°, and Z = 2.     

Synthesis,Structural Characterization,and Cation Transport of Tripotassium Pentabismuth Arsenate K3Bi5(AsO4)6

During the exploration of the K₂O-Bi₂O ₃ -As₂O₅ system, single crystals of a new arsenate of trivalent bismuth, K₃Bi₅(AsO₄) ₆, were isolated by solid state reaction at 600°C. The title compound crystallizes in the monoclinic system, space group C2/c (N°15) with a = 18.257(2) Å, b = 7.260(1) Å, c = 20.130(4) Å, β = 119.86(1)°, and Z = 4. Its structure consists of a three-dimensional framework made up of AsO₄ tetrahedra and BiO₆ and BiO₇ polyhedra sharing edges and corners, delimiting cavities wherein K⁺ ions reside. This compound exhibits a potassium ion conductivity but with rather low conductivity value.     

Syntheses and Crystal Structures of Rb2B2Se7, Tl2B2Se7, Cs3B3Se10, and Tl3B3Se10: New Perseleno‐selenoborates with Polymeric Anionic Chains

The perseleno‐selenoborates Rb₂B₂Se₇ and Cs₃B₃Se₁₀ were prepared from the metal selenides, amorphous boron and selenium, the thallium perseleno‐selenoborates Tl₂B₂Se₇ and Tl₃B₃Se₁₀ directly from the elements in evacuated carbon coated silica tubes by solid state reactions at temperatures between 920 K and 950 K. All structures were refined from single crystal X‐ray diffraction data. The isotypic perseleno‐selenoborates Rb₂B₂Se₇ and Tl₂B₂Se₇ crystallize in the monoclinic space group I 2/a (No. 15) with lattice parameters a = 12.414(3) Å, b = 7.314(2) Å, c = 14.092(3) Å, β = 107.30(3)°, and Z = 4 for Rb₂B₂Se₇ and a = 11.878(2) Å, b = 7.091(2) Å, c = 13.998(3) Å, β = 108.37(3)° with Z = 4 for Tl₂B₂Se₇. The isotypic perseleno‐selenoborates Cs₃B₃Se₁₀ and Tl₃B₃Se₁₀ crystallize in the triclinic space group P1 (Cs₃B₃Se₁₀: a = 7.583(2) Å, b = 8.464(2) Å, c = 15.276(3) Å, α = 107.03(3)°, β = 89.29(3)°, γ = 101.19(3)°, Z = 2, (non‐conventional setting); Tl₃B₃Se₁₀: a = 7.099(2) Å, b = 8.072(2) Å, c = 14.545(3) Å, α = 105.24(3)°, β = 95.82(3)°, γ = 92.79(3)°, and Z = 2). All crystal structures contain polymeric anionic chains of composition ([B₂Se₇]^2–)_n or ([B₃Se₁₀]^3–)_n formed by spirocyclically fused non‐planar five‐membered B₂Se₃ rings and six‐membered B₂Se₄ rings in a molar ratio of 1 : 1 or 2 : 1, respectively. All boron atoms have tetrahedral coordination with corner‐sharing BSe₄ tetrahedra additionally connected via Se–Se bridges. The cations are situated between three polymeric anionic chains leading to a nine‐fold coordination of the rubidium and thallium cations by selenium in M₂B₂Se₇ (M = Rb, Tl). Coordination numbers of Cs⁺ (Tl⁺) in Cs₃B₃Se₁₀ (Tl₃B₃Se₁₀) are 12(11) and 11(9).     

Cs4[IrO4], ein neues Iridat mit planarem Anion [IrO4]4−

Cs₄[IrO₄], a New Iridate with Planar Anion [IrO₄]^4? For the first time we obtained black single crystals of Cs₄[IrO₄] by heating intimate mixtures of CsO_0.52 and IrO₂ (molar ratio Cs : Ir = 4.30 : 1.00; “Ag-bomb”, 740°C/86 d). Cs₄[IrO₄] crystallizes monocline, C 2/m, with a = 1031.66(8) pm, b = 671.61(4) pm, c = 660.44(6) pm, b? = 108.118(7)° and Z = 2 in the K₄[IrO₄]-type. The structure has been determined by four-circle-diffractometer data (PW 1100 from Phillips, Ag? Kα , graphite) with 841 I₀(hkl) with I ≥ 3s?(F) (from 947 I₀(hkl) out of 3529 measured reflexes). The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Über Cs2Li2[GeO4]

About Cs₂Li₂[GeO₄] By heating of a well-ground mixture of the binary oxides CsO_0.55, Li₂O and GeO₂ (Cs:Li:Ge=2,6:2,2:1; Ni-tube; 600 °C; 49d) we got single crystals of Cs₂Li₂[GeO₄] for the first time. Cs₂Li₂[GeO₄] is isotypic to Rb₂Li₂[MO₄] [M = Si, Ti, Ge] [2] and Cs₂Li₂[MO₄] (M = Si, Ti) [3]: according to this Cs₂Li₂[GeO₄] crystallizes triclinic, in the spacegroup P1 with a = 968.7(4) pm, b = 586.0(2) pm, c = 571.4(2) pm, α = 92.71(4)°, β = 110.95(3)° and γ = 94.34(4)° (Guinier-Simon data), Z = 2. The structure was determined by four-circle diffractometer data (Ag? K_α ; 2381 I_o(hkl); R = 8,4%; R_w = 5.0%), parameters see text. Further the Madelung Part of Lattice Energy (MAPLE), Effective Coordination Numbers (ECoN) and the Mean Fictive Ionic Radii (MEFIR), have been calculated.     

Die Kristallstruktur von Lithiummesitolat [{LiOC6H2-2,4,6-(CH3)3}4(THF)3]

X-Ray Structure of [{LiOC₆H₂-2,4,6-(CH₃)₃}₄(THF)₃] The title compound crystallized from a THF/OEt₂ solution. Its crystal structure (monoclinic, P2₁/c, a = 21.362(3), b = 13.441(2), c = 17.188(2) Å, β = 98.39(1)°, Z = 4, R = 0,0911, wR² = 0,2562) is built up by cuban-like tetrameric units. Three of the four Li cations attain a coordination number of four by binding to an additional THF molecule. Li(4) without THF coordination has a short distance to one ortho-methyl group (Li(4)…C(27) 2.669(10) Å). The Li–O_ph bonding distances vary from 1.869(10) to 2.051(10) Å (average 1.97 Å); the average bonding distance for Li–O_THF is 2.012(10) Å. Averaged bonding angles for Li–O_ph–Li′ and O_ph–Li–O′_ph amount to 84.4(4)° and 95.4(4)°, respectively. The Li…Li distances significantly differ from each other. They range from 2.556(12) to 2.739(11) Å (average 2.65(1) Å).     

The Crystal Structure of Tl2Te3 – a Reinvestigation

Crystals of the title compound were obtained by annealing a powder of Tl₂Te₃ in a vertical temperature gradient (230 °C–240 °C, 4 weeks). Tl₂Te₃ crystallizes in space group C2/c with lattice parameters of a = 13.275(1) Å, b = 6.562(1) Å, c = 7.918(1) Å, and β = 107.14°(2). The tellurium atoms form chains [Te₃^2–], consisting of interconnected linear triatomic · Te–^Te–Te · groups which are isosteric with XeF₂. The Te–Te distances of the XeF₂-like units are 3.02 Å, the connecting ones 2.83 Å.