Synthesis and structure of two crystalline modifications of Bis(1,10-Phenanthroline)trinitratoeuropium(III) Eu(NO3)3(Phen)2

Two crystalline modifications (I and II) of the phenanthroline complex of europium nitrate with the same chemical composition, Eu(NO₃)₃(Phen)₂, are synthesized under different conditions by varying the solvents, temperatures, and crystallization rates. The crystal structures of these modifications are determined using X-ray diffraction. Crystalline modifications I and II differ in the unit cell parameters and the positions of the complexes in the unit cell. The geometric characteristics of the complexes in the structures of compounds I and II differ insignificantly. Crystals of compound I belong to the isostructural family Ln(NO₃)₃(Phen)₂ (Ln = La-Lu). Crystals of compound II (new phase) are studied for the first time. Crystals of I and II are monoclinic, space group C2/c, and Z = 4. The unit cell parameters are as follows: a = 11.1555(10) Å, b = 17.9698(10) Å, c = 13.0569(10) Å, β = 100.507(10)°, and V = 2572.1(3) ų for modification I and a = 9.5153(10) Å, b = 15.4546(10) Å, c = 17.1763(10) Å, β = 93.451(10)°, and V = 2521.3(3) ų for modification II. The difference between the molecular complexes in the structures of compounds I and II is revealed by the superposition method. Complexes II are arranged along the C ₂ axis and are statistically disordered with respect to this axis.     

Crystal structures of mixed compounds Cu(2)Gly(D-Ser)(L-Ser)2 and Cu(2)Gly 3(L-Ser)

-The crystal structures of mixed coordination compounds, Cu(2)Gly(D-Ser)(L-Ser)₂(I) and Cu(2)Gly ₃(L-Ser)(II), which contain the amino acid residues of glycine (Gly) and serine (Ser) in the 1: 3 and 3: 1 ratio, respectively, are studied by electron diffraction. Crystals I and II are triclinic, Z = 1, and space group P1. For I, a = 8.96(2) Å, b = 9.66(2) Å, c = 5.07(2) Å, α = β = 90°, and γ = 92.8(3)°. For II, a = 8.37(2) Å, b = 9.65(2) Å, c = 5.06(2) Å, α = β = 90°, and γ = 92.8(3)°. Compounds I and II have layered structures that are based on the CuGly(L-Ser) fragment. Structures I and II differ mainly in their interlayer spacing and configuration of the interlayer space.     

Crystal structures and properties of isomers of 3,5-dinitro-(4-acetylphenyl)aminobenzoyl (p-bromophenyl)amide

The para and ortho isomers of 3,5-dinitro-(4-acetylphenyl)aminobenzoyl (p-bromophenyl)amide (I and II, respectively) are synthesized, and their physicochemical properties and structure are investigated. The para isomer I has a higher melting temperature and is less soluble in organic solvents as compared to the ortho isomer II. The electronic absorption spectra indicate that absorption for molecule I occurs at longer wavelengths than for molecule II. A correlation between the physicochemical properties and the crystal structures of compounds I and II is revealed. Crystals I · 0.5C₆H₆ are triclinic; the unit cell parameters are a = 11.760(2) Å, b = 13.958(3) Å, c = 15.012(3) Å, α = 108.01(2)°, β = 103.95(1)°, γ = 92.00(2)°, V = 2258.3(8) ų, space group $P\bar 1$ , and Z = 4. Crystals II are monoclinic; the unit cell parameters are a = 9.302(2) Å, b = 16.380(3) Å, c = 13.480(3) Å, β = 100.09(3)°, V = 2022.1(7) ų, space group P2₁/c, and Z = 4. Structures I · 0.5C₆H₆ and II are characterized by intramolecular and intermolecular hydrogen bonds.     

X-Ray diffraction and IR-spectroscopic studies of UO2(n-C3H7COO)2(H2O)2 and Mg(H2O)6[UO2(n-C3H7COO)3]2

Single crystals of UO₂(n-C₃H₇COO)₂(H₂O)₂ (I) and Mg(H₂O)₆[UO₂(n-C₃H₇COO)₃]₂ (II) are synthesized. Their IR-spectroscopic and X-ray diffraction studies are performed. Crystals I are monoclinic, a = 9.8124(7) Å, b = 19.2394(14) Å, c = 12.9251(11) Å, β = 122.423(1)°, space group P2₁/c, Z = 6, and R = 0.0268. Crystals II are cubic, a = 15.6935(6) Å, space group $Pa\bar 3$ , Z = 4, and R = 0.0173. The main structural units of I and II are [UO₂(C₃H₇COO)₂(H₂O)₂] molecules and [UO₂(C₃H₇COO)₃]^? anionic complexes, respectively, which belong to AB ₂ ⁰¹ M ₂ ¹ (I) and AB ₃ ⁰¹ (II) crystal chemical groups of uranyl complexes (A = UO ₂ ²⁺ , B ⁰¹ = C₃H₇COO^?, and M ¹ = H₂O). A crystal chemical analysis of UO₂ L ₂ · nH₂O compounds, where L is a carboxylate ion, is performed.     

Synthesis and crystal structure of new double indium phosphates M 3 I In(PO4)2 (M I = K and Rb)

Double potassium indium and rubidium indium phosphates K₃In(PO₄)₂ (I) and Rb₃In(PO₄)₂ (II) are synthesized by solid-phase sintering at T = 900°C. The compounds prepared are characterized by X-ray powder diffraction (I and II), X-ray single-crystal diffraction (II), and laser-radiation second harmonic generation. Structure I is solved using the Patterson function and refined by the Rietveld method. Both compounds crystallize in the monoclinic crystal system. For crystals I, the unit cell parameters are as follows: a = 15.6411(1) Å, b = 11.1909(1) Å, c = 9.6981(1) Å, β = 90.119(1)°, space group C2/c, R _p = 4.02%, and R _wp = 5.25%. For crystals II, the unit cell parameters are as follows: a = 9.965(2) Å, b = 11.612(2) Å, c = 15.902(3) Å, β = 90.30(3)°, space group P2₁/n, R ₁ = 4.43%, and wR ₂ = 10.76%. Structures I and II exhibit a similar topology of the networks which are built up of { In[PO₄]₂} (I) and { In₂[PO₄]₄} (II) structural units.     

Synthesis and structure of oxovanadium(IV) complexes [VO(<Emphasis Type="Italic">Acac</Emphasis>)<Subscript>2</Subscript>] and [VO(<Emphasis Type="Italic">Sal</Emphasis>: <Emphasis Type="Italic">L</Emphasis>-alanine)(H<Subscript>2</Subscript>O)]

Bis(acetylacetonato)oxovanadium C₁₀H₁₄O₅V (I) and (S)-[2-(N-salicylidene)aminopropionate]oxovanadium monohydrate C₁₀H₉NO₅V (II) are synthesized. The crystal structures of compounds I and II are determined using single-crystal X-ray diffraction. Crystals of compound I are triclinic, a = 7.4997(19) Å, b = 8.2015(15) Å, c = 11.339(3) Å, α = 91.37(2)°, β = 110.36(2)°, γ = 113.33(2)°, Z = 2, and space group \(P\bar 1\). Crystals of compound II are monoclinic, a = 8.5106(16) Å, b = 7.373(2) Å, c = 9.1941(16) Å, β = 101.88(1)°, Z = 2, and space group P2₁. The structures of compounds I and II are solved by direct methods and refined to R₁ = 0.0382 and 0.0386, respectively. The oxovanadium complexes synthesized are investigated by vibrational spectroscopy.     

Crystal structure and vibrational spectra of two cadmium halide complexes with 1,2-Bis[2-(Diphenylphosphinylmethyl)phenoxy]ethane (L 1) and 1,3-bis[2-diphenylphosphinylmethyl)phenoxy]propane (L), CdBr2 ⋅ L 1 and CdI2 ⋅ L

Two cadmium halide complexes with 1,2-bis[2-(diphenylphosphinylmethyl)phenoxy]ethane (L ¹) and 1,3-bis[2-(diphenylphosphinylmethyl)phenoxy]propane (L), namely, CdBr₂ ? L ¹ (I) and CdI₂ ? L(II), have been synthesized. An analysis of their vibrational spectra is carried out. The structures of I and II are determined by X-ray diffraction. Crystals I are monoclinic, a = 31.562(6) Å, b = 13.548(3) Å, c = 18.733(4) Å, β = 91.28(3)°, space group C2/c, Z = 8, and R = 0.051 for 3776 reflections. Crystals II are triclinic, a = 11.803(2) Å, b = 12.554(3) Å, c = 14.686(3) Å, α = 90.30(3)°, β = 90.29(3)°, γ = 106.08(3)°, space group $P\bar 1$ , Z = 2, and R = 0.043 for 4916 reflections. Compounds I and II exhibit a polymeric chain structure. The potentially tetradentate ligands L ¹ and L are coordinated to the metal atoms only through two phosphoryl oxygen atoms and fulfill the bidentate bridging function. The environment of the Cd atom is completed to the tetrahedral coordination by two Br atoms in complex I and two I atoms in complex II. The mean distances are as follows: Cd-Br, 2.526(2) Å; Cd-I, 2.695 Å; and Cd-O, 2.243(8) Å in I and 2.210(4) Å in II. The L ¹ and L ligands in complexes I and II adopt an S-shaped conformation.     

Crystal structures of double vanadates, Ca9 R(VO4)7 ⋅ III. R = Nd, Sm, Gd, or Ce

The crystal structures of Ca₉ R(VO₄)₇ (R = Nd (I), Sm (II), or Gd (III)) were studied by the Rietveld method. The compounds are isostructural to Ca₃(VO₄)₂ and are crystallized in the trigonal system (sp. gr. R3c, Z = 6). The unit-cell parameters are as follows: for I, a = 10.8720(5) Å, c = 38.121(1) Å; for II, a = 10.8652(5) Å, c = 38.098(1) Å; and for III, a = 10.8631(5) Å, c = 38.072(1) Å. In the structures of I and II, the M(1), M(2), and M(3) positions are statistically occupied by the rare-earth cations and calcium anions. In the structure of III, the Gd³⁺ cations occupy the _M(1) and _M(2) positions. The distributions of the R ³⁺ cations over the positions are characteristic of each structure. The composition of the cerium-ontaining compound Ca_9.81Ce_0.42(VO₄)₇ (a = 10.8552(5) Å, c = 38.037(1) Å) was refined and its crystal structure was solved from the X-ray powder data. In this compound, cerium atoms are in the oxidation states +3 and +4.     

Synthesis and structure of zirconium and 3d-transition metal phosphates M 0.5Zr2(PO4)3(M = Mn, Co, Ni, Cu, Zn)

Double zirconium and 3d-transition metal phosphates of the compositions M 0.5Zr2(PO4)3[M = Mn (I), Co (II), Ni (III), Cu (IV), Zn (V)] have been synthesized and the types of their structures have been refined. Compounds I, II, III, IV, and V are all monoclinic (sp. gr. P2₁/n, Z = 4) and have the unit cell parameters a = 12.390(3), 12.389(3), 12.385(3), 12.389(3), 12.389(2) Å; b = 8.931(4), 8.928(3), 8.924(4), 8.925(4), 8.929(3) Å; c = 8.843(3), 8.840(2), 8.840(3), 8.841(3), 8.842(2) Å, β = 90.55(1), 90.54(1), 90.53(1), 90.53(1), 90.54(1)°; V = 978.5, 977.7, 977.0, 977.4, 978.1 ų, respectively. All the structures have the {[Zr₂(PO₄)₃]^?}3_∞-type frameworks. The crystallographic data for 3d-transition and alkali earth metal phosphates described by the general formula M _0.5Zr₂(PO₄)₃ are compared.     

Effect of the acid-base interactions in a solution on the composition of the coordination sphere of aluminum and gallium complexonates

Hydroxocomplexonate K₂[GaEdta(OH)] · 6H₂O (I) and nitronium salts BH⁺GaEdta · 4H₂O (II) and BH⁺AlEdta · 4H₂O (IV) are synthesized from aqueous solutions at pH 8, 6, and 7, respectively. AlHEdta(H₂O) (III) is isolated from an acid solution (pH 1.5). Structures I, II, and IV are determined by single-crystal X-ray diffraction. The X-ray powder diffraction analysis of III has revealed that its crystals are not isostructural with those of similar complexes of other metals. Crystals I–IV are monoclinic. The unit cell parameters are a = 10.482(1), 15.735(4), 5.768(4), and 15.756(4) Å; b = 10.442(2), 12.511(2), 14.884(11), and 12.453(3) Å; c = 19.590(4), 17.330(5), 19.113(12), and 17.328(6) Å; β = 101.30(2)°, 104.54(2)°, 90.74(5)°, and 104.75(2)° for I–IV, respectively.     

Synthesis and crystal structures of nitratocobaltates Na2[Co(NO3)4], K2[Co(NO3)4], and Ag[Co(NO3)3] and potassium nitratonickelate K2[Ni(NO3)4]

The cobalt(II) and nickel(II) nitrate complexes with an island structure (Na₂[Co(NO₃)₄] (I) and K₂[Co(NO₃)₄] (II)] and a chain structure [Ag[Co(NO₃)₃] (III) and K₂[Ni(NO₃)₄] (IV)] are synthesized and investigated using X-ray diffraction. In the anionic complex [Co(NO₃)₄]^2? of the crystal structure of compound I, the Co coordination polyhedron is a twisted tetragonal prism formed by the O atoms of four asymmetric bidentate nitrate groups. In the anion [Co(NO₃)₄]^2? of the crystal structure of compound II, one of the four NO₃ groups is monodentate and the other NO₃ groups are bidentate (the coordination number of the cobalt atom is equal to seven, and the cobalt coordination polyhedron is a monocapped trigonal prism). The crystal structures of compounds III and IV contain infinite chains of the compositions [Co(NO₃)₂(NO₃)_2/2]^? and [Ni(NO₃)₃(NO₃)_2/2]^2?, respectively. In the crystal structure of compound III, seven oxygen atoms of one monodentate and three bidentate nitrate groups form a dodecahedron with an unoccupied vertex of the A type around the Co atom. In the crystal structure of compound IV, the octahedral polyhedron of the Ni atom is formed by five nitrate groups, one of which is terminal bidentate. The data on the structure of Co(II) coordination polyhedra in the known nitratocobaltates are generalized.     

Crystal structures of cesium and dimethylammonium cupradecaborates, Cs[CuB10H10] and (CH3)2 NH2[CuB10H10]

The crystal structures of Cs[CuB₁₀H₁₀] (I) and (CH₃)₂NH₂[CuB₁₀H₁₀] (II) are studied (R = 0.0398 and 0.0510 for 1225 and 2728 observed reflections in I and II, respectively). Crystals I and II are built of [(CuB₁₀H₁₀)^?]∞ anionic chains and cations. The distorted tetrahedral coordination of the Cu⁺ ions is formed by four pairs of B-H atoms from two polyhedral anions. The Cu-B bond lengths in I and II are 2.159–2.287(6) and 2.130–2.285(9) Å, respectively. The coordination of the Cu⁺ ions in II includes only edges between apical and equatorial vertices of the anions. In I, both the edges of the apical belt and those between two equatorial vertices are involved in coordination. The ability of the B₁₀H ₁₀ ^2? anion to coordinate metals by the equatorial edge is established for the first time.     

X-ray structure investigation of 1-acetoxy-1-cyano-2-naphthylethylene and 1,1-dicyano-2-naphthylethylene

The crystal structures of 1-acetoxy-1-cyano-2-naphthylethylene (I) and 1,1-dicyano-2-naphthylethylene (II) are determined by X-ray structure analysis. Crystals I are monoclinic; at 25° C, the unit cell parameters are as follows: a = 17.308(6) Å, b = 4.507(1) Å, c = 17.845(5) Å, β = 107.90(2)°, V = 1324.7(7) ų, d _calcd = 1.260 g/cm³, Z = 4, and space group P2₁/n. Crystals II are monoclinic; at 25°C, the unit cell parameters are a = 3.827(1) Å, b = 15.784(4) Å, c = 17.226(2) Å, β = 91.22(2)°, V = 1040.3(4) ų, d _calcd = 1.304 g/cm³, Z = 4, and space group P2₁/n. It is revealed that, in crystal structures of I and II, the molecular stacks characteristic of compounds of this series are formed through stacking contacts along the direction of the smallest lattice parameter.     

Crystal structures of molecular complexes of 18-crown-6 with 2-aminobenzoic and 5-amino-1-benzyl-1,2,3-triazole-4-carboxylic acid hydrazides

The crystal structures of two host-guest molecular complexes of 18-crown-6 with 2-aminobenzoic acid hydrazide monohydrate (the ratio host: guest: H₂O = 1: 2: 2) (complex I) and 5-amino-1-benzyl-1,2,3-triazole-4-carboxylic acid hydrazide (the host: guest ratio = 1: 2) (complex II) are determined by X-ray diffraction analysis. Crystals I are monoclinic, a = 8.468(2) Å, b = 17.378(3) Å, c = 10.517(2) Å, β = 96.88(3)°, space group P2₁/n, and R = 0.0393 for 6692 reflections. Crystals II are orthorhombic, a = 18.489(1) Å, b = 10.192(3) Å, c = 20.412(2) Å, space group Pbca, and R = 0.0540 for 3513 reflections. In both complexes, the centrosymmetric 18-crown-6 and guest molecules are joined together through the NH?O (crown) hydrogen bonds, which involve all the hydrogen atoms of the hydrazine group. The NH?O=C intramolecular hydrogen bond is observed in the guest molecule. In structure I, the water molecule serves as a bridge between the guest molecules related by the glide-reflection plane and combines the guest-host-guest complexes into layers. In structure II, the guest molecules are linked into chains through hydrogen bonds of the NH?O=C type; in turn, the chains composed of guest molecules and the crown ether molecules bonded to these chains form a layered structure.     

Crystal structure of double vanadates Ca9 R(VO4)7. II. R = Tb, Dy, Ho, and Y

Crystal structures of the compounds Ca₉ R(VO₄)₇ (R = Tb (I), Dy (II), Ho (III), and Y (IV) have been studied by the method of the full-profile analysis. All the compounds are crystallized in the trigonal system (sp. gr. R 3 c, Z = 6) with the unit-cell parameters (I) a = 10.8592(1), c = 38.035(1), V = 3884.2(2) ų; (II) a = 10.8564(1), c = 38.009(1) Å, V = 3879.6(2) ų, (III) a = 10.8565(1) and c = 37.995(1) Å, V = 3878.3(2) ų, and (IV) a = 10.8588(1), c = 37.995(1) Å, V = 3879.9(2) ų. In structures I–IV, rare earth and calcium cations occupy three positions—M(1), M(2), and M(5). Rare earth cations occupy the R ³⁺ positions almost in the same way: 2.7–2.6(2) cations in the M(1) position; 2.7–2.3(2) cations in the M(2) position, and 0.6–1.0(1) cation in the M(5) position. At the same time, the occupancy of the M(5) position regularly increases with a decrease of the R ³⁺ radius.     

Stereochemical activity of a lone electron pair in antimony(III) and bismuth(III) chelates: Crystal structures of Ca[Sb(Edta)]2 ⋅ 8H2O and Ba{[Bi(Edta)] 2H2O ⋅ H2O

The crystal structures of Ca[Sb(Edta)]₂ ? 8H₂O (I) and Ba{ [Bi(Edta)]₂H₂O} ? H₂O (II) are determined by X-ray diffraction. Crystals I are monoclinic, a = 7.132 Å, b = 21.906 Å, c = 10.896 Å, β = 91.13°, Z = 2, and space group P2₁/n. Crystals II are triclinic, a = 8.995 Å, b = 12.750 Å, c = 13.577 Å, α = 77.42°, β = 73.90°, γ = 86.53°, Z = 2, and space group $P\bar 1$ . In structure I, the coordination number of the antimony atom is 6 + LEP (lone electron pair), and the polyhedron is a ψ-pentagonal bipyramid with the lone electron pair at an equatorial position. In structure II, two crystallographically independent complexes Bi(Edta)^? and the coordination water molecule form tetranuclear associates. The environments of two independent bismuth atoms (the coordination number is eight) are similar, and their polyhedra can be described as distorted dodecahedra. The effect of the lone electron pair on the structures of polyhedra of antimony and bismuth is discussed.     

X-ray mapping in heterocyclic design: XI. X-ray diffraction study of 1-benzoyl-3-(pyridin-2-yl)-thiocarbamide and the product of its reaction with oxidants

The structures of 1-benzoyl-3-(pyridin-2-yl)-thiocarbamide C₁₃H₁₁N₃O₁S₁ (I) and 2-benzoylimino-1,2,4-thiadiazole[2,3-a]pyridine C₁₃H₉N₃O₁S₁ (II) are studied by X-ray diffraction. Structures I [a = 5.342(4) Å, b = 20.428(5) Å, c = 11.784(4) Å, β = 90.55(2)°, Z = 4, space group P2₁/n) and II [a = 6.258(6) Å, b = 18.068(14) Å, c = 10.185(10) tA, β = 95.45(8)°, Z = 4, space group P2₁/n) are determined by direct methods and refined to R ₁ = 0.0673 and 0.0802, respectively. In structure I, both intramolecular (involving the O atom) and intermolecular (involving the N and S atoms) hydrogen bonds are observed. The latter bonds are responsible for the formation of centrosymmetric molecular dimers. In structure II, a short intramolecular contact (2.168 Å) is observed between the S and O atoms.     

Synthesis and crystal structure of (CN3H6)2[UO2(OH)2(NCS)]NO3 and β-Cs3[UO2(NCS)5]

Compounds (CN₃H₆)₂[UO₂(OH)₂(NCS)]NO₃ (I) and β-Cs₃[UO₂(NCS)₅] (II) are synthesized and studied by IR spectroscopy and single-crystal X-ray diffraction. I and II crystallize in the orthorhombic system. For I, a = 12.2015(13) Å, b = 7.3295(8) Å, c = 16.310(2) Å, space group Pnma, Z = 4, and R = 0.0327; for II, a = 21.7891(6) Å, b = 13.5120(3) Å, c = 6.8522(2) Å, space group Pnma, Z = 4, and R = 0.0268. In structure I, complex groups form infinite chains [UO₂(OH)₂(NCS)] _n ^n? belonging to the AM ₂ ² M ¹ crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , M ² = OH^?, and M ¹ = NCS^?). The main structural elements of crystals II are mononuclear [UO₂(NCS)₅]^3? groups belonging to the AM ₅ ¹ group of uranyl complexes (A = UO ₂ ²⁺ and M ¹ = NCS^?). In I and II, uranium-containing complexes are connected with outer-sphere cations by electrostatic interactions, and in I a system of hydrogen bonds also contributes to their binding. Specific features of the packing of complex [UO₂(NCS)₅]^3? groups in the structures of two modifications of Cs₃[UO₂(NCS)₅] are discussed.     

Molecular and crystal structures of 1R,4S-2-(4-carbomethoxy)benzylidene-n-menthan-3-one

The molecular and crystal structures of chiral 1R,4S-2-(4-carbomethoxy)benzylidene-n-menthan-3-one (I) are determined by X-ray diffraction analysis. Crystals I are orthorhombic; at 20°C: a = 11.961(3) Å, b = 26.453(8) Å, c = 5.400(2) Å, space group P2₁2₁2₁, and Z = 4 (C₁₉H₂₅O₃). In molecule I, the cyclohexanone ring with the axial methyl and isopropyl substituents adopts a chair conformation. It is found that the enone and arylidene fragments of compound I have a substantially nonplanar structure. The shortened intramolecular contacts between atoms of the arylidene grouping and the α fragment of the cyclohexanone ring and their associated distortions of bond angles at the sp ² carbon atoms are the common structural features of 2-arylidene-n-menthan-3-ones irrespective of the stereochemical configuration of the C(4) chiral center.     

Structure studies of solid solutions of oxygen in electrolytic niobium

The crystal structures (cubic system, sp. gr. Im3m) of solid solutions of oxygen in niobium of the Compositions NbO _x<0.01 (I), NbO_0.150(6) (II) and NbO_0.107(5) (III) were studied for the first time by single-crystal X-ray diffraction analysis (Syntex P1 diffractometer, λMoKα radiation). Crystals I (a = 3.2969(8) Å) and II (a = 3.3082(6) Å) were prepared by the electrolysis of salt melts. Crystal III (a = 3.3114(4) Å) was obtained after partial dissolution of crystal I in a solution of HNO₃, HCl, and HF resulting in its saturation with oxygen. The residual electron density maps for crystal I revealed no O atoms. Localization of the O atoms in the tetrahedral cavities of crystal II and in the tetrahedral and octahedral cavities of crystal III indicates that the arrangement of the interstitial positions of oxygen atoms depends on the procedure of preparing solid solutions. In crystals II and III, the amplitudes of thermal vibrations of the Nb atoms are smaller and the anharmonicity of these vibrations is higher than those in crystal I virtually devoid of oxygen. The reasons for the substantially higher oxygen content (up to 17 at. %) in cubic crystals of the solid solutions of O in Nb prepared by the electrolytic method than in the analogous phase obtained upon heating (lower than 7 at. %) are discussed.