Intra- vs intermolecular hydrogen bonding. The crystal structure of 5-methyl-2-hydroxyacetophenone thiosemicarbazone monohydrate and salicylaldehyde-2-methylthiosemicarbazone monohydrate

The crystal structure of 5-methyl-acetophenonethiosemicarbazone monohydrate,A, and salicylaldehyde-2-methylthiosemicarbazone monohydrate,B, were determined using single crystal X-ray diffraction.A crystallizes in the monoclinic space groupC2/c, with lattice parametersa=14.161(2),b=15.753(1) Å,c=11.084(1) Å, β=112.59(1)° andZ=4, yielding a calculated density ofD _calc=1.352 mg/m³.B crystallizes in the triclinic space groupP1, witha=7.233(2) Å,b=7.371(2) Å,c=11.841(2) Å, α=82.77(2)°, β=78.33(2)°, γ=63.06(2)° andD _calc=1.371 mg/m³ forZ=2,. In bothA andB the immine nitrogen and the sulfur atom areanti with respect to N2-C8. WhileA presents the usual intramolecular six membered hydrogen bond ring,B has instead an intermolecular hydrogen bond between the hydroxy moiety of the salicyladehyde and a water molecule. AM1 calculations agree with the experimental conformations observed in both compounds.     

Structural investigation of 1-amino-2,4,6-trinitrobenzenes in the solid state and in solution

The crystal structure of 1-pyrrolidino-2,4,6-trinitrobenzene3, 1-morpholino-2,4,6-trinitrobenzene4 and 1-piperidino-2,4,6-trinitrobenzene5 have been determined by single-crystal X-ray diffraction data and the structure in solution was investigated by UV-visible spectrophotometry and¹³C nmr. The three compounds are monoclinic, space groupP2_i/n. Unit cell dimensions area=6.6660(1),b=8.612(1),c=20.696(3) Å, β=90.73(1)^o, andD _c =1.58 g cm^?3 for compound3;a=7.090(2),b=21.493(9),c=8.298(3) Å, β=101.27(1)^o, andD _c 1.60 g cm^?3 for compound4 anda=10.426(1),b=10.038(1),c=12.291(1) Å, β=90.04(1)^o withD _c =1.53 g cm^?3 for compound5 forZ=4. In the solid state, differences regarding the planarity of the aromatic ring in the three substrates were found. Rotation of theortho-nitro groups and of the amino group out of the aromatic plane was observed both in the solid state and in the solution. Greater coplanarity of the two rings was found in3 than in4 and5.     

CO replacement in Ru3(CO)12 by 2,3-bis(diphenylphosphino)maleic anhydride (bma). X-ray structures of Ru3(CO)10(bma)·H2O and

Thermolysis of Ru₃(CO)₁₂ with 2,3-bis(diphenylphosphino)maleic anhydride (bma) in toluene solution gives the new compounds Ru₃(CO)₁₀(bma) (2), Ru₂(CO)₆(bma) (3), and (4). All compounds have been isolated and characterized in solution by IR and³¹P NMR spectroscopy. The solid-state structures of2, as the monohydrate, and4 were established by X-ray crystallography. Ru₃(CO)₁₀(bma)·H₂O crystallizes in the monoclinic space groupC2/c,a=12.741(2) Å,b=19.548(2) Å,c=32.973(4) Å, β=96.847(9)°,V=8154(2) ų,Z=8,d _calc=1.740 g cm^?3;R=0.046,R _w =0.051 for 2541 observed reflections withl>3σ(l). The bma ligand in2 is bound to the triruthenium frame in a bridging fashion, with equatorially disposed PPh₂ groups. The X-ray structure of2 reveals an extreme twisting of the maleic anhydride ring away from the plane defined by the plane of the three ruthenium atoms, along with a significant lengthening of the maleic anhydride C=C π bond. crystallizes in the monoclinic space groupP2₁/c,a=9.3113(5) Å,b=18.164(1) Å,c=20.097(1) Å, β-102.021(4)°,V=3324.5(3) ų,Z=4,d _calc=1.671 g cm^?3;R=0.024,R _w =0.030 for 3499 observed reflections withl>3σ(l). The presence of the μ₂ moiety and P?C (maleic anhydride) bond cleavage attendant in the formation of4 are confirmed by X-ray analysis. The relationship of the compounds3 and4 to the dimeric compounds Ru₂(CO)₆(bpcd) and [where bpcd=4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione] is discussed. Independent studies dealing with Ru₃(CO)₁₀(bma) (bridging isomer) have shown that cluster2 is stable in toluene solution at elevated temperature and does not afford compounds3 and4, suggesting the intermediacy of the putative chelating isomer of Ru₃(CO)₁₀(bma) (1) as the source of3 and4.     

Crystal structures of 1,1′-di(2-propanone)-2,2′-biimidazole dihydrazone and 2,6-diacetylpyridine dihydrazone

The nucleophilic addition reactions between 1,1′-di(2-propanone)-2,2′-biimidazole or 2,6-diacetylpyridine and hydrazine hydrate afford 1,1′-di(2-propanone)-2,2′-biimidazole dihydrazone (1) and 2,6-diacetylpyridine dihydrazone (2), respectively. Compound1 crystallizes in the orthorhombic space groupP2₁2₁2₁, witha=9.042(2),b=9.731(3),c=15.683(4)Å, V = 1379.9(6)Å^? andZ=4. Compound2 crystallizes in the orthorhombic space groupPnma, witha=10.948(2),b=19.742(6),c=4.566(1)Å, V=986.9(4)Å^? andZ=8. A pseudo center of inversion is present at the midpoint of the C?C bond joining the imidazole rings of1, whose substituents crystallize in atrans configuration. The imidazole rings are rotated 2.5(3)° about the C?C bond. In contrast to the essentially planar structure of2, the hydrazone substituent groups of1 are at angles of 89.9(1)° and 88.4(1)° with respect to the plane of the adjacent imidazole moiety.     

Aryl acetylene inhibitors for cytochrome P450-based monooxygenase isozymes

The structures of 1-propynylpyrene (1), 4-ethynylbiphenyl (2), 3-ethynylphenanthrene (3), 9-propynylphenanthrene (4) and 9-ethynylphenenthrene (5) have been determined using MoKα radiation.1 crystallizes in the monoclinic space groupP2₁/n witha=8.972(2)b=10.136(2),c=14.060(2)Å, β=99.77(1)°,V=1260.0(7) ų,Z=4. Refinement of 1261 reflections gaveR=0.042 andR _w =0.054.2 crystallizes in the orthorhombic space groupPbcn witha=17.7159(9),b=6.250(2),c=18.544(2) Å,V=2053(1) ų,Z=8. Refinement of 1710 observed reflections gaveR=0.046 andR _w =0.053.3 crystallizes in the orthorhombic space group Pbca witha=7.891(1),b=16.459(1),c=16.879(2) Å,V=2192.2(7) ų,Z=8. Refinement of 1520 observed reflections gaveR=0.032 andR _w =0.047.4 crystallizes in the orthorhombic space groupP2₁2₁2₁ witha=5.8867(6),b=13.476(1).c=14.838(2) Å,V=1177.1(4) ų,Z=4. Refinement of 1217 observed reflections gaveR=0.041 andR _w =0.055.5 crystallizes in the monoclinic space groupP2₁/c witha=27.755(7),b=5.1447(9),c=15.500(2) Å, β-105.53(2)°,Z=2133(2) ų,Z=8. There are two independent molecules in the unit cell. Refinement of 1276 observed reflections gaveR=0.061 andR _w =0.065. In2–5 there are no significant intermolecular interactions while in1 the molecules are associated in pairs via π-π stacking intarctions. Bond distances within the pyrene and phenanthrene portions of the molecules compare favorably with those found in other derivatives.     

The crystal and molecule structure of three 2,4,6-trinitrobenzene derivatives:α,α,α-trifluoro-2,4,6-trinitrotoluene (C7H2F3N3O6), 2,4,6-trinitrobenzamide (C7H4N4O7), 2,4,6-trinitrobenzoic acid (C7H3N3O8)

The crystal and molecular structures of three 2,4,6-trinitrobenzene derivatives have been determined. Forα,α,α-trifluoro-2,4,6-trinitrotoluene (1): monoclinic,P2₁/n,a=7.510(2),b=9.273(2),c=14.984(0) Å,β=99.02(2)°,V=1028.1(4)° ų,Z=4,D=1.816 g cm^?3,R(F)=0.051, andR(wF)=0.055. For 2,4,6-trinitrobenzamide (2): orthorhombic,Pbca,a=9.248(3),b=14.377(6),c=17.729(4) Å,V=1958(1) ų,Z=8,D=1.737 g cm^?3,R(F)=0.073, andR(wF)=0.077. For 2,4,6-trinitrobenzoic acid (3): orthorhombic,P2₁2₁2₁,a=6.553(1),b=11.405(2),c=12.796(2) Å,V=956.3(3) ų,Z=4,D=1.785 g cm^?3,R(F)=0.045, andR(wF)=0.046.1 crystallizes as discrete molecules,2 as weakly hydrogen-bonded dimers and3 as a chiral polymer of hydrogen-bonded helices. In1, the presence of the nonplanar CF₃ substituent causes a large twisting of theα-nitro groups out of the plane of the benzene ring, whereas the nearly planar C(O)NH₂ and C(O)OH substituents in2 and3 are perpendicular to the benzene plane and do not cause a significant rotation of theα-nitro groups.     

Assignment of relative configurations and conformational analysis of α-phenylacyliron complexes (η5-C5H5)Fe(CO)(PPh3)(COCHRPh). X-ray structural determinations of two complexes (η5-C5H5)Fe(CO) (PPh3)(COCHPhR), R=CHOHCH3 and R=COH(CH3)2

Conformational analysis of the alkylation and aldol condensation products of phenylacetyliron complex (4), based on¹H-NMR chemical shifts and¹H-¹H vicinal coupling constants, permitted the assignment of relative configurations to all products obtained. Configurations and conformations of two aldol condensation products,12A and13F, were determined by X-ray structural analysis and were compared with the structures deduced from¹H-NMR data. The crystals of12A and13F are monoclinic, space group of12A isP2₁/_n with cell dimensions:a=10.937(2),b=17.278(5),c=16.412(3)Å, andβ=107.52(2)°; space group of13F isP2₁/c, with cell dimensions:a=11.576(4),b=21.180(2),c=11.854(4)Å, andβ=99.80(3)°. Both structures were solved by direct methods, and refined by a full-matrix, least-squares procedure giving for12A R=0.0599 and for13F R=0.0459.     

The structure of the π-molecular complex between 1,4-dihydro-9,10-anthrahydroquinone and 1,4-dihydro-9,10-anthraquinone

The structure of the π-molecular complex (10) was assigned on the basis of the solid state¹³C-nmr spectrum. The solid state¹³C-nmr spectrum of quinhydrone (12) has also been determined. Accurate¹H and¹³C chemical shift assignments have been made for the compounds3,5,6,7,8, and10 on the basis of HMQC and HMBC spectral data. The π-molecular complex10 crystallizes in the space groupP2₁ In with cell parameters:a=4.052 (1) Å,b=6.477 (1) Å,c=19.093 (2) Å, β=90.17 (1)^o,z=1,D _c =1.400 g mc^?32. Crystal and molecular structure of the title compound, C₂₈H₂₂O₄, has been determined by an X-ray analysis of10 by direct methods from diffractometer data and refined by full-matrix least-squares     

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 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.     

Synthesis and the crystal and molecular structure of two modifications of bis(1,10-phenanthroline)trinitratoerbium(III) Er(NO3)3(Phen)2

Two crystalline modifications (I and II) of the phenanthroline complex of erbium nitrate with the same chemical composition, Er(NO₃)₃(Phen)₂, are synthesized by a procedure similar to that used for preparing the phenanthroline complexes of europium nitrate. The crystal structures of these modifications are determined using X-ray diffraction. Crystals of compound I belong to the isostructural family Ln(NO₃)₃(Phen)₂ (Ln = La-Lu). Crystals of compound II are isostructural to those of modification II (new phase) of the Eu(NO₃)₃(Phen)₂ compound. Crystals of I and II are monoclinic, space group C2/c, and Z = 4. The unit cell parameters are as follows: a = 11.126 Å, b = 17.815 Å, c = 12.976 Å, β = 100.45°, and V = 2529 ų for modification I and a = 9.459 Å, b = 15.463 Å, c = 17.076 Å, β = 93.52°, and V = 2493 ų for modification II. The molecular complexes in the structures of compounds I and II are nearly identical. The mean lengths of the Er-N and Er-O bonds are equal to 2.500 and 2.466 Å in compound I and 2.508 and 2.457 Å in compound II, respectively. The difference between the structures of compounds I and II is associated with the difference between intermolecular interactions in the unit cell.     

Crystal Structures of Diphosphinated Chromium Fischer Amino Carbenes

The crystal structures of four new diphosphinated chromium Fischer amino carbenes with the compositions fac-[(P-P)(CO)₃Cr=C(NR₂′)(R)] (R = Me, NR₂′ = pyrrolidino, P-P = dppe, 1; R = Me, NR₂′ = pyrrolidino, P-P = dppp, 2; R = Me, R′ = Me, P-P = dppe, 3; R = Me, R′ = Me, P-P = dppp, 4) have been determined at 243 K. Compound 1 crystallizes in the monoclinic system, space group P2₁ /n with a = 12.1597(11) Å, b = 20.1556(17) Å, c = 14.0557(12) Å, β = 114.163(3)°, V = 3143.0(5) Å³, and Z = 4. Compound 2 crystallizes in the triclinic system, space group P ? 1 with a = 7.4424(3) Å, b = 10.8830(5) Å, c = 20.6040(9) Å, α = 100.9880(10)°, β = 91.7650(10)°, γ = 97.6610(10)°, V = 1620.90(12) Å³, and Z = 2. Compound 3 crystallizes in the monoclinic system as a mono-solvate of d⁵-pyridine, space group P2₁ /c with a = 11.485(2) Å, b = 22.825(5) Å, c = 14.092(3) Å, β = 108.53(3)°, V = 3502.7(12) Å³, and Z = 4. Compound 4 crystallizes in the orthorhombic system, space group P2 ₁ 2 ₁ 2 ₁ with a = 8.359(3) Å, b = 15.364(6) Å, c = 23.784(9) Å, V = 3055(2) Å³, and Z = 4. Steric repulsions with the diphosphine ligand favor a conformation with the amino moiety directed away from the diphosphine backbone in 1–4.     

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.     

Ether cleavage of [2.2.2]cryptand: synthesis and X-ray crystal structure of [NH(CH2CH2I)3][I5]

Treatment of [2.2.2]cryptand1 in toluene with HI(g) has resulted in the formation of a twophase liquid clathrate solution from which the complex [NH(CH₂CH₂I)₃][I₅]2 has been isolated and crystallographically characterized. Crystal data for2: triclinic, space group $P\bar 1$ ,a=9.301(3) Å,b=10.419(3) Å,c=11.078(3) Å, α=90.20(2)^o, β=103.28(2)^o γ=96.50(2)^o,D _c =3.57g/cm³,Z=2,R _f =0.054,R _w =0.054. The salt is a product of an ether cleavage of the macrobicycle. The crystal structure of2 contains [NH(CH₂CH₂I)₃]⁺ ions and zigzag chains of [I₅]^? ions which self-assemble to form alternating layers, of cations and anions.     

Crystal structures of benzo-18-crown-6 complexes with oxonium hexafluorotantalate and oxonium hexafluoroniobate

The crystal structures of [(benzo-18-crown-6) · H₃O]TaF₆ and [(benzo-18-crown-6) · H₃O]NbF₆ complex compounds are determined by X-ray diffraction. It is revealed that the tantalum complex has two polymorphic modifications, namely, the monoclinic (I) and orthorhombic (II) modifications. The unit cell parameters of these compounds are as follows: a = 14.784(2) Å, b = 8.390(4) Å, c = 18.005(6) Å, β = 95.78(2)°, Z = 4, and space group P2₁/n for modification I; and a = 8.456(2) Å, b = 21.967(5) Å, c = 24.122(5) Å, Z = 8, and space group Pbca for modification II. The orthorhombic niobium complex [(benzo-18-crown-6) · H₃O]NbF₆ with the unit cell parameters a = 8.454(1) Å, b = 21.943(3) Å, c = 24.127(4) Å, Z = 8, and space group Pbca (III) is isostructural with tantalum complex II. The oxonium cation in complexes I–III is encapsulated by the crown ether and thus forms one ordinary and two bifurcate hydrogen bonds with the oxygen atoms of the crown ether. This macrocyclic cation is bound to the anions through the C-H ...F contacts (H...F, 2.48–2.58 Å).     

Formation of copper(II) coordination polymers by a flexible double betaine: [{Cu(L)X2(H2O)} n ]·2nH2O [X=Cl,Br] and [{Cu(L)(H2O)4} n ](ClO4)2n ·2nH2O [L=−O2CCH (Me3N+)CH2CH2CH(Me3N+)CO 2 − ]

Three polymeric copper(II) complexes of a flexible double betaine, namely, [{Cu(L)Cl₂(H₂O)} _n ]·2 _n H₂O (1), [{Cu(L)Br₂(H₂O)} _n ]·2nH₂O (2), and [{Cu(L)(H₂O)₄} _n ](ClO₄)_2n ·2nH₂O (3) [L=?O₂CCH(Me₃N⁺)CH₂CH₂CH(Me₃N⁺CO₂], have been prepared and characterized by singlecrystal X-ray analysis. Isomorphous complexes (1) and (2) crystallize in space groupC2/c (No. 15) witha=17.725(3),b=5.958(2),c=19.077(3) Å, β=110.70(1)^o,V=1881.4(4) ų, Z=4 anda=18.268(4),b=5.948(3),c=19.166(5) Å, β=109.08(2)^o,V=1964.7(9) ų, Z=4, respectively. Complex (3) belongs to space groupPī (No. 2) witha=6.203(1),b=9.293(2),c=12.035(2) Å, α=86.56(2), β=87.33(3), γ=71.23(2)^o,V=655.4(2) ų and Z=1. The crystal structure of (1) and (2) features an infinite zigzag chain composed of an alternate arrangement of metal atoms and double betaines ligands, with each Cu(II) atom in a distorted CuX₂O₃ [X-Cl, Br] square-pyramidal geometry, and hydrogen bonding between adjacent chains leads to a layer structure concentrated the (200) family of planes. Complex (3) exhibits a layer structure corresponding to the (001) family of planes, in which neighboring chains constructed from the metal atoms and the double betaine ligands are cross-linked by hydrogen bonding between the aqua ligands. The Cu(II) atom is coordinated in a CuO₆ octahedral geometry with Jahn-Teller distortion.     

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.     

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.     

Reaction of CpRu(PPh3)2Cl with six-member cyclothioethers. Structures of the [CpRu(PPh3) x L]Y complexes (L = pentamethylene sulfide, x = 2, Y = BF4 −; L = 1,3-dithiane; 1,3,5-trithiane, x = 2, Y = CF3SO3 −; L = 1,4-dithiane, x = 1, Y = BF4 −)

The synthesis of a series of ruthenium complexes with cyclothioether ligands is reported. The compounds were characterized by X-ray diffraction techniques. The molecular structures of [CpRu(PPh₃)₂(pms)]BF₄ (1), [CpRu(PPh₃)₂(1,3-dithiane)]OTfl (2), [CpRu(PPh₃)₂(1,3,5-trithiane)]OTfl (3), and [CpRu(PPh₃)(1,4-dithiane)]BF₄ (4) show chelation occurs only when the sulfur atoms are separated by at least two C atoms, creating a ligand bite size large enough to chelate. Cell parameters: 1, space group P2₁/c, a = 14.601(4), b = 19.102(10), c = 14.751(7) Å, β = 98.28(3)^○; 2, space group P2₁/c, a = 12.859(7), b = 15.576(3), c = 22.126(11) Å, β = 102.22(4)^○; 3, space group P2₁/c, a = 12.7320(20), b = 15.571(5), c = 22.287(4) Å, β = 101.812(14)^○; 4, space group Pbca, a = 11.2010(10), b = 16.321(7), c = 28.966(4) Å. Compounds 2 and 3 are X-ray isomorphous. The Ru–S bond lengths range from 2.341(3), 2.365(3) Å in compound 4 to 2.382(4) Å in compound 2. Upon chelation (compound 4), with subsequent loss of PPh₃, the Ru–P bond shortens to 2.327(3) Å. This may be due to reduced steric hindrance about the Ru atom. No evidence for C–S bond lengthening is observed.     

Tetrahydrophthalic esters of prednisolone

The two biologically active isomers of prednisolone tetrahydrophthalate have been studied by X-ray diffraction methods. The compounds crystallize in the orthorhombic system in the space groupP2₁2₁2₁, with similar lattice parameters. The isomers differ both in configuration [(1′S),(6′R) isomerA and (1′R),(6′S) isomerB] and conformation of the thetetrahydrophthalic part of the molecules. Cell parameters of isomerA:a=9.595(2),b=14.465(2),c=18.988(3) Å andB:a=9.114(2),b=14.283(6),c=20.398(5) Å. The O(3) carbonyl oxygen atom interactsvia hydrogen bonds with three neighboring molecules accepting hydrogen bonds from two hydroxyl groups and one carboxylic group. Additional short intermolecular C?H…O type contacts occur in the structure of theB isomer, which has a somewhat larger unit cell and significantly higher melting point.