Synthese und Kristallstruktur von ACu4As2 (A: Ca–Ba,Eu)

Synthesis and Crystal Structure of A Cu₄As₂ ( A : Ca–Ba, Eu) Steel‐gray single crystals of ACu₄As₂ with A = Ca–Ba and Eu respectively were synthesized by heating mixtures of the elements at about 900 °C. Structure determinations with X‐ray diffractometry data revealed, that the isotypic compounds crystallize in the rhombohedral CaCu₄P₂ type structure (R3m; Z = 3) (hexagonal axes see ”︁Inhaltsübersicht”︁”︁). Measurements of the susceptibility of EuCu₄As₂ showed divalent Eu and ferromagnetic order at 35 K.     

Quaternäre Chloride des zweiwertigen Europiums mit dreiwertigen Übergangsmetallen: Synthese und Kristallstruktur von Na6Eu3M4Cl24 (M = Ti,V, Cr)

Quaternary Chlorides of Divalent Europium and Trivalent Transition Metal Ions: Synthesis and Crystal Structure of Na₆Eu₃M₄Cl₂₄ (M = Ti, V, Cr) The reaction of EuCl₂, NaCl and MCl₃ (M = Ti, V, Cr) yields the chlorides Na₆Eu₃M₄Cl₂₄. According to X‐ray single crystal investigations, their crystal structure is a variant of the monoclinic cryolite‐type structure. One crystallographic site is occupied by Na1 and Eu simultaneously. For charge compensation the Na2 site is not fully occupied. In Na₆Eu₃Ti₄Cl₂₄ (P2₁/n, Z = 1/2, a = 663.8(1) pm, b = 718.3(1) pm, c = 953.3(2) pm, β = 91.55(2)°, R_all = 0.0314), Na₆Eu₃V₄Cl₂₄ (P2₁/n, Z = 1/2, a = 660.4(1) pm, b = 715.8(1) pm, c = 946.5(2) pm, β = 91.41(2)°, R_all = 0.0313) and Na₆Eu₃Cr₄Cl₂₄ (P2₁/n, Z = 1/2, a = 654.8(1) pm, b = 706.5(1) pm, c = 945.4(2) pm, β = 91.07(2)°, R_all = 0.0368) the ratio of Na1 : Eu amounts to 5 : 3. The colours of the compounds, orange yellow for M = Ti, orange red for M = V and dark red for M = Cr, indicate electronic interactions between Eu²⁺ and M³⁺.     

BaClSCN und Na4Mg(SCN)6: Zwei neue wasserfreie Thiocyanate der Erdalkalimetalle

BaClSCN and Na₄Mg(SCN)₆: Two New Thiocyanates of the Alkaline Earth Metals The reaction of BaCl₂ and NaSCN yielded single crystals of BaClSCN (P 2₁/m, Z = 2, a = 588.6(1) pm, b = 465.8(1) pm, c = 864.4(2) pm, β = 100.20(3)°, R_all = 0.0214). According to X‐ray single crystal investigations, the structure consists of anionic SCN^– and Cl^– layers, respectively, alternating in [001] direction. The SCN^–‐ions are connected via the N and the S atoms to the cations. Na₄Mg(SCN)₆ (P 3 1c, Z = 2, a = 863.8(1) pm, c = 1399.3(2) pm, R_all = 0.0870), which was obtained from a melt of NaSCN and MgCl₂, consists of anionic layers with the cations between the sheets. The holes are filled altenatingly by Na⁺ or Na⁺ and Mg²⁺. Regarding only the C‐atoms of the SCN^– group, the structure can be described as a hexagonal closest packing whith the cations occupying 5/6 of the octahedral voids.     

Similar Coordination – Different Dimensionality: Synthesis,Single Crystal Structures,and Theoretical Studies of Hydrogen‐bonded {[Ca(H2O)2L4]I2}n/∞ (1: L = CH3COOC2H5, n = 1; 2: L = OC4H8, n = 2)

CaI₂(H₂O)₂ reacts with O‐donor ligands L to yield coordination compounds of the type {[Ca(H₂O)₂L₄]I₂}_n/∞, ( 1 : L = CH₃COOC₂H₅, n = 1; 2 : L = THF, n = 2). Both compounds feature a coordination number of six around the calcium atom with two water molecules in axial positions and four ligands L in equatorial positions of a tetragonal bipyramid. Due to only a slight variation in the arrangement of the cationic units [Ca(H₂O)₂L₄]²⁺, hydrogen bonds can be built up between them and the iodide anions in different ways in order to lead to a one‐dimensional polymer for 1 and a two‐dimensional polymer for 2 . Density functional theory calculations provide useful informations on the involved orbitals on the μ₂‐bridging iodide and on the structure of the systems, leading to a small H–I–H angle of 71.2° in 1 compared to a large H–I–H angle of 121.8° in 2 .     

Hg2(CH3SO3)2: Synthese,Kristallstruktur, thermisches Verhalten und Schwingungsspektroskopie

Hg₂(CH₃SO₃)₂: Synthesis, Crystal Structure, Thermal Behavior, and Vibrational Spectroscopy Colorless single crystals of Hg₂(CH₃SO₃)₂ are formed in the reaction of HgO, Hg, and HSO₃CH₃. In the monoclinic compound (I2/a, Z = 4, a=883.2(2), b=854.0(2), c=1188.9(2) pm, β = 92.55(2)°, R_all=0.0445) the Hg₂²⁺ ion is coordinated by two monodentate CH₃SO₃^— anions. Further contacts Hg‐O occur in the range from 262 to 276 pm and lead to a linkage of the [Hg₂(CH₃SO₃)₂] units. The thermal analysis shows that Hg₂(CH₃SO₃)₂ decomposes at 300° yielding elemental mercury. The mass numbers of the species evolved lead to the assumtion that SO₃, SO₂, CO₂, CO and H₂CO are formed during the reaction. In the IR and the Raman spectrum the typical vibrations of the CH₃SO₃^— ion are observed, the Raman spectrum shows the Hg‐Hg stretching vibration at 177 cm^—1 within the Hg₂²⁺ ion additionally.     

Die Clusterazide M2[Nb6Cl12(N3)6]·(H2O)4—x (M = Ca,Sr, Ba)

The Cluster Azides M₂[Nb₆Cl₁₂(N₃)₆]·(H₂O)_4—x (M = Ca, Sr, Ba) The isotypic cluster compounds M₂[Nb₆Cl₁₂(N₃)₆] · (H₂O)_4—x (M = Ca (1) , M = Sr (2) and M = Ba (3) ) have been synthesized by the reaction of an aequeous solution of Nb₆Cl₁₄ with M(N₃)₂. 1 , 2 and 3 crystallize in the space group Fd3¯ (No. 227) with the lattice constants a = 1990.03(23), 2015.60(12) and 2043, 64(11) pm, respectively. All compounds contain isolated 16e— clusters whose terminal positions are all occupied by orientationally disordered azide ligands.     

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.     

Disupersilylsilanide M(SiHR*2)2 der Zinkgruppenmetalle (M = Zn,Cd, Hg; R* = SitBu3): Synthesen,Charakterisierung und Strukturen

Disupersilylsilanides M(SiHR^*₂)₂ of Metals of the Zinc Group (M = Zn, Cd, Hg; R* = Si t Bu₃): Syntheses, Characterization, and Structures Bis(disupersilyl)silylmetals M(SiHR )₂ (R* = Supersilyl = SitBu₃) with M = Zn, Cd, Hg are obtained in tetrahydrofuran/benzene/pentane by the reaction of NaSiHR with ZnCl₂, CdI₂, HgCl₂ in the molar ratio 2 : 1. The compounds form colorless, in organic media soluble, not hydrolysis‐ and air‐sensitive crystals, the stabilities of which for thermolysis or photolysis decrease in the row Zn > Hg > Cd compound. According to X‐ray structure analyses, the compounds M(SiHR )₂ are monomeric with a – to date not observed – non‐linear framework –M– (angle SiMSi for M(SiHR )₂ with M = Zn/Cd/Hg 170.7/174.2/174.4°).     

Synthese und Kristallstruktur von Hydrogenselenaten zweiwertiger Metalle – M(HSeO4)2 (M = Mg,Mn, Zn) und M(HSeO4)2 · H2O (M = Mn,Cd)

Synthesis and Crystal Structure of Hydrogen Selenates of Divalent Metals – M(HSeO₄)₂ (M = Mg, Mn, Zn) and M(HSeO₄)₂ · H₂O (M = Mn, Cd) New hydrogen selenates M(HSeO₄)₂ (M = Mg, Mn, Zn) and M(HSeO₄)₂ · H₂O (M = Mn, Cd) have been synthesized using MSeO₄ (M = Mg, Mn, Zn, Cd) and 90% selenic acid as starting materials. The crystal structures have been determined by X-ray single crystal crystallography. The compounds M(HSeO₄)₂ (M = Mg, Zn) belong to the structure type of Mg(HSO₄)₂, whereas Mn(HSeO₄)₂ forms a new structure type. Both hydrogen selenate monohydrates are isotypic to Mg(HSO₄)₂ · H₂O. In all compounds the metal atoms are octahedrally coordinated by oxygen atoms of different HSeO₄-tetrahedra. In the HSeO₄-tetrahedra the Se–OH-distances (mean value 1.70 Å) are about 0.1 Å longer than Se–O-distances (mean value 1.62 Å). In the structure of M(HSeO₄)₂ (M = Mg, Zn) there are zigzag chains of hydrogen bonded HSeO₄-tetrahedra. The structure of Mn(HSeO₄)₂ is characterized by chains of HSeO₄-tetrahedra in form of screws. Hydrogen bonds from and to water molecules connect double layers of MO₆-octahedra and HSeO₄-tetrahedra in the structures of M(HSeO₄)₂ · H₂O.     

(NH4)3[M2NCl10] (M = Nb,Ta): Synthese,Kristallstruktur und Phasenumwandlung

(NH₄)₃[M₂NCl₁₀] (M = Nb, Ta): Synthesis, Crystal Structure, and Phase Transition The nitrido complexes (NH₄)₃[Nb₂NCl₁₀], and (NH₄)₃[Ta₂NCl₁₀] are obtained in form of moisture-sensitive, tetragonal crystals by the reaction of the corresponding pentachlorides with NH₄Cl at 400 °C in sealed glass ampoules. Both compounds crystallize isotypically in two modifications, a low temperature form with the space group P4/mnc and a high temperature form with space group I4/mmm. In case of (NH₄)₃[Ta₂NCl₁₀] a continuous phase transition occurs between –70 °C and +60 °C. For the niobium compound this phase transition is not yet fully completed at 90 °C. The structure of (NH₄)₃[Nb₂NCl₁₀] was determined at several temperatures between –65 °C und +90 °C to carefully follow the continuous phase transition. For (NH₄)₃[Ta₂NCl₁₀] the structure of the low temperature form was determined at –70 °C, and of the high temperature form at +60 °C. The closely related crystal structures of the two modifications contain NH₄⁺ cations and [M₂NCl₁₀]^3– anions. The anions with the symmetry D_4h are characterized by a symmetrical nitrido bridge M=N=M with distances Nb–N = 184.5(1) pm at –65 °C or 183.8(2) pm at 90 °C, and Ta–N = 184.86(5) pm at –70 °C or 184.57(5) pm at 60 °C.     

Synthese und Einkristallstrukturanalyse von [M(NH3)6]C60 · 6 NH3 (M = Co2+, Zn2+)

Synthesis and Single Crystal Structure Analysis of [M(NH₃)₆]C₆₀ · 6 NH₃ (M = Co²⁺, Zn²⁺) [M(NH₃)₆]C₆₀ · 6 NH₃ (M = Co²⁺, Zn²⁺) was synthesized from K₂C₆₀ by ion exchange in liquid ammonia. According to single crystal structure analyses the new fullerides are isostructural to the respective Mn, Ni and Cd compounds. The deformation patterns of the C₆₀^2– anions are similar within this group of compounds. However, there are no indications for significant deformations of the cages as a whole, which could be attributed to a Jahn‐Teller distortion.     

ACu9X4 ‐ Neue Verbindungen mit der CeNi8, 5Si4, 5‐Struktur (A: Sr,Ba; X: Si,Ge)

ACu₉X₄ ‐ New Compounds with CeNi_{8, 5}Si_{4, 5} Structure (A: Sr, Ba; X: Si, Ge) The new compounds SrCu₉Si₄ (a = 8.146(1), c = 11.629(2)Å), BaCu₉Si₄ (a = 8.198(2), c = 11.735(2)Å), SrCu₉Ge₄ (a = 8.273(2), c = 11.909(5)Å), and BaCu₉Ge₄ (a = 8.338(4), c = 12.011(7)Å) are formed by reaction of the elements at 1000° ‐ 1100 °C. They are isotypic (I4/mcm, Z = 4) and crystallize in an ordered variant of the cubic NaZn₁₃ type structure, also built up by the binary phase BaCu₁₃. In the ternary compounds the positions of Cu2 are orderly occupied by copper and silicon and germanium, respectively. This results in a lowering of symmetry and a distortion of the polyhedra. The metallic conductivity of the compounds was confirmed by measurements on BaCu₉Si₄.     

Darstellung und Kristallstruktur des TetramethylammoniumthiocyanatSchwefeldioxid‐Adduktes, (CH3)4N+SCN– · SO2

Preparation and Crystal Structure of the Tetramethylammonium Thiocyanate Sulfur Dioxide Adduct, (CH₃)₄N⁺SCN^– · SO₂ Tetramethylammonium thiocyanate reacts with sulfur dioxide under formation of tetramethylammonium thiocyanate sulfur dioxide adduct. The resulting salt is characterised by NMR and vibrational spectroscopy and its crystal structure. (CH₃)₄N⁺SCN^– · SO₂ crystallizes in the monoclinic space group P2₁/c with a = 578.4(1) pm, b = 1634.3(1) pm, c = 1054.6(1) pm, β = 105.17(1)°, and four formula units in the unit cell. The crystal structure possesses a strong S–S interaction between the NCS^– anion and the SO₂ molecule. The NCS–SO₂ distance of 301.02(9) pm is longer than a covalent single bond, thus the compound is rather described as an adduct. The structure is compared with ab initio calculated data.     

Neue thermische Abbauprodukte von Ln2CeMO6Cl3 (M = Nb,Ta; Ln = La–Sm) – Darstellung von strukturverwandtem (La, Tb)3,5TaO6Cl4–x

Contributions on the Investigation of Inorganic Nonstoichiometric Compounds. XLV. New Thermal Decomposition Products of Ln₂CeMO₆Cl₃ – Preparation of Structure‐related (La, Tb)_3.5TaO₆Cl_4–x The thermal decomposition (T £ 900–1050°C) of Ln₂CeMO₆Cl₃ (M = Nb, Ta; Ln = La, Ce, Pr, Nd, Sm) leads to the formation of two mixed‐valenced phases (Ln, Ce)_3.25MO₆Cl_3.5–x (phase ‘‘AB”︁”︁) and (Ln, Ce)_3.5MO₆Cl_4–x (phase ‘‘BB”︁”︁) and to the formation of chlorine according to redox‐reactions between Ce⁴⁺ and Cl^–. Single crystals of both phases (Ln, Ce)_3.25MO₆Cl_3.5–x (‘‘AB”︁”︁) and (Ln, Ce)_3.5MO₆Cl_4–x (‘‘BB”︁”︁) were obtained by chemical transport reactions using both powder of Ln₂CeMO₆Cl₃ (phase ‘‘A”︁”︁) and powder of (Ln, Ce)_3.25MO₆Cl_3.5–x (phase ‘‘AB”︁”︁) as starting materials and chlorine (p{Cl₂; 298 K} = 1 atm) or HCl (p{HCl; 298 K} = 1 atm) as transport agent. A crystal of (La, Ce)_3.25NbO₆Cl_3.5–x (”︁AB”︁”︁) (space group: C2/m, a = 35.288(1) Å, b = 5.418(5) Å, c = 9.522(1) Å, β = 98.95(7)°, Z = 4) was investigated by x‐ray diffraction methods, a crystal of (Pr, Ce)_3.5NbO₆Cl_4–x (”︁BB”︁”︁) was investigated by synchrotron radiation (λ = 0.56 Å) diffraction methods. The lattice constants are a = 18.863(6) Å, b = 5.454(5) Å, c = 9.527(6) Å, β = 102.44(3)° and Z = 4. Structure determination in the space group C2/m (No. 12) let to R1 = 0.0313. Main building units are NbO₆‐polyhedra with slightly distorted trigonally prismatic environment for Nb and chains of face‐sharing Cl₆‐octahedra along [010]. The rare earth ions are coordinated by chlorine and oxygen atoms. These main structure features confirmed the expected relation to the starting material Ln₂CeMO₆Cl₃ (phase ”︁A”︁”︁) and to (Ln, Ce)_3.25MO₆Cl_3.5–x (phase ”︁AB”︁”︁).     

Stabilisierung von M+‐Ionen (M = In,Tl) durch Dibenzyldichlorogallat

Stabilization of M⁺ Ions (M = In, Tl) by Dibenzyldichlorogallate MCl reacts with (PhCH₂)₂GaCl to give M[(PhCH₂)₂GaCl₂] [M = In ( 1 ), Tl ( 2 )]. 1 and 2 were characterized by NMR, IR and MS techniques. In addition, an X‐ray structure determination of 1 was performed. According to this, 1 consists of four‐membered In₂Cl₂ rings connected by weak In…Cl contacts (344 pm) along [010] to a coordination polymer. The In⁺ ion is coordinated by four In–Cl and two In‐aryl interactions.     

Über die Koexistenz von tetragonalem und monoklinem CaC2: Strukturelle und spektroskopische Untersuchungen an Erdalkalimetallacetyliden,MC2 (M = Ca,Sr, Ba)

On the Coexistence of Tetragonal and Monoclinic CaC₂: Structural and Spectroscopic Studies on Alkaline Earth Metal Acetylides, MC₂ (M = Ca, Sr, Ba) The alkaline earth acetylides CaC₂, SrC₂ and BaC₂ can be considered to occur in three polymorphic structures each. The monoclinic low-temperature form, the tetragonal form, and the cubic high-temperature form. No deviation from axial symmetry is obtained for the C₂^2– ions in the tetragonal structure determinations, as confirmed by X-ray single-crystal structures and ¹³C MAS NMR studies. The CaC₂ samples prepared by us were always a mixture of monoclinic and tetragonal phase. Their Raman spectra exhibited two distinct C₂ streching vibrations. Problems arising from the coexistence of these two phases for the interpretation of ¹³C MAS NMR spectra are discussed.     

Darstellung,Struktur und magnetische Eigenschaften von Erdalkali-Mangan-Verbindungen AMnX mit A = Mg,Ca, Sr,Ba und X = Si,Ge, Sn

Preparation, Structure, and Magnetic Properties of the Alkaline Earth Manganese Compounds AMnX with A = Mg, Ca, Sr, Ba and X = Si, Ge, Sn The new compounds MgMnGe, MgMnSn, CaMnSi, CaMnSn, and SrMnSn were prepared by reaction of the elements. They crystallize tetragonally with the anti-PbFCl type structure (space group P4/nmm). The lattice constants see ”︁Inhaltsübersicht”︁”︁. Using a Faraday balance, magnetic measurements in the range 4.2 to 800 K were performed with the new substances and with the already known compounds CaMnGe, SrMnGe, and BaMnGe. They indicate metamagnetic behaviour at low temperatures. At high temperatures twodimensional magnetic interactions between the manganese atoms seem to persist. The construction of an unexpensive heating device for the Faraday balance is described.     

Kristallstrukturen der Monofluorosulfite MSO2F (M = K,Rb)

Crystal Structures of Monofluorosulfites MSO₂F (M = K, Rb) Single crystals of potassium and rubidium fluorosulfite were obtained for the first time by reacting the alkali metal fluorides with sulfur dioxide in acetonitrile at 75 °C. According to the results of X‐ray structure determinations they are isotypic (monoclinic, P2₁/m, Z = 2, KSO₂F: a = 696.2(2), b = 566.3(2), c = 465.8(1) pm, β = 107.73(2)°, RbSO₂F: a = 717.2(1), b = 586.7(1), c = 484.0(1) pm, β = 107.14(1)°) and structurally analogous to potassium chlorate. In contrast to potassium fluoroselenite in which the complex anions are polymerized to linear chains by unsymmetric fluorine bridges, the fluorosulfite anion is isolated. The S–F‐distance of 159.1(2) pm (KSO₂F) corresponds to a S–F single bond, the S–O‐distance of 152.6(2) pm indicates a bond order of 1.5.     

Untersuchungen zur Darstellung von [CpxSb{M(CO)5}2] (Cpx = Cp,Cp*; M = Cr,W)

Investigations of the Synthesis of [Cp^xSb{M(CO)₅}₂] (Cp^x = Cp, Cp*; M = Cr, W) The reaction of CpSbCl₂ with [Na₂{Cr₂(CO)₁₀}] leads to the chlorostibinidene complex [ClSb{Cr(CO)₅}₂(thf)] ( 1 ), whereas the reaction of CpSbCl₂ with [Na₂{W₂(CO)₁₀}] results in the formation of the complexes [ClSb{W(CO)₅}₃] ( 2 ), [Na(thf)][Cl₂Sb{W(CO)₅}₂] ( 3 ), [ClSb{W(CO)₅}₂(thf)] ( 4 ) and [Sb₂{W(CO)₅}₃] ( 5 ). The stibinidene complex [CpSb{Cr(CO)₅}₂] ( 6 ) is obtained by the reaction of [ClSb{Cr(CO)₅}₂] with NaCp, while its Cp* analogue [Cp*Sb{Cr(CO)₅}₂] ( 7 ) is formed via the metathesis of Cp*SbCl₂ with [Na₂{Cr₂(CO)₁₀}]. The products 2 , 3 , 4 and 7 are additionally characterised by X‐ray structure analyses.     

IR- und Raman-Spektren der isotypen Iodathydrate M(IO3)2 · 4 H2O (M = Mg,Ni, Co); Kristallstruktur von Co(IO3)2 · 4 H2O

Infrared and Raman Spectroscopy of the Isostructural Iodate Hydrates M(IO₃)₂ · 4 H₂O (M = Mg, Ni, Co)-Crystal Structure of Cobalt Iodate Tetrahydrate The iodate tetrahydrates Mg(IO₃)₂ · 4 H₂O, β-Ni(IO₃)₂ · 4 H₂O, Co(IO₃)₂ · 4 H₂O and their deuterated specimens were studied by X-ray, infrared and Raman spectroscopic methods. The title compounds are isostructural crystallising in the monoclinic space group P2₁/c (Z = 2). The crystal structure of Co(IO₃)₂ · 4 H₂O (a = 836.8(5), b = 656.2(3), c = 850.2(5) pm and β = 100.12(5)°) has been refined by single-crystal X-ray methods (R_obs = 3.08%, 693 unique reflections I₀ > 2σ(I)). Isolated Co(IO₃)₂(H₂O)₄ octahedra form layers parallel (100). Within these layers, the two crystallographically different hydrate water molecules form nearly linear hydrogen bonds to adjacent IO₃^– ions (ν_OD of matrix isolated HDO of Co(IO₃)₂ · 4 H₂O (isotopically diluted samples) 2443 (H3), 2430 (H2), and 2379 cm^–1 (H1 and H4), –180 °C). Intramolecular O–H and intermolecular H…O distances were derived from the novel ν_OD vs. r_OH and the traditional ν_OD vs. r_H…O correlation curves, respectively. The internal modes of the iodate ions of the title compounds are discussed with respect to their coupling with the librations of the hydrate H₂O molecules, the distortion of the IO₃^– ions, and the influence of the lattice potential.