Photochemical synthesis and structural characterization of (η-C5Me5)3Mo3(CO)4(μ2-H)(μ3-O): an unprecedented 46-electron trimolybdenum cluster containing a localized monoprotonated Mo---Mo double bond

Irradiation of the 30-electron Mo₂(η⁵-C₅Me₅)₂(CO)₄ and Re₂(CO)₁₀ in toluene solution (containing H₂O) afforded (in 1–2% yields) a novel triangular metal cluster, (η⁵-C₅Me₅)₃Mo₃(CO)₄(η₂-H)(η₃-O) (1), which was characterized by a single-crystal X-ray diffraction study. Compound 1, of pseudo C_s-m symmetry, has a triangulo-Mo₃(η₃-O) core with composite Mo---H---Mo and Mo---Mo electron-pair bonds along one unusually short edge (2.660(1) Å) and Mo--- electron-pair bonds along the other two edges (2.916(1) and 2.917(1) Å). The edge-bridged hydride ligand, which displays a characteristic high-field proton NMR resonance at δ −17.79 ppm, was not found from the crystallographic determination but was located via a quantitative potential-energy-minimization method. This procedure unambiguously established that the optimized hydrogen position, which corresponds to a distinct coordination site with identical Mo---H distances of 1.85 Å, is the only one that can be sterically occupied by a metal-bound hydride ligand. This 46-electron species is the first electron-deficient trimolybdenum cluster containing a monoprotonated Mo---Mo double bond; its existence is attributed to ligand overcrowding due to the bulky pentamethylcyclopentadienyl rings. Black (η⁵- C₅Me₅)₃Mo₃(CO)₄(η₂-H)(η₃-O) · 1/2THF crystallizes with two formula species in a triclinic unit cell of P1 symmetry with a 8.603(4), b 11.115(4), c 19.412(11) Å, 80.69(4)°, β 101.10(4)°, and γ 98.88(3)° at −40° C. Least-squares refinement (RAELS with 221 variables) of one independent Mo₃ molecule and a centrosymmetrically-disordered THF molecule converged at R₁(F) 5.62%, R₂(F 6.88% for 8460 independent diffractometry data (I₀ ρ 3σ(I₀ collected at −40° C with Mo-K radiation     

Oxygen abstraction from tetrahydrofuran by molybdenum-iodide complexes. X-ray molecular structure of [Mo2(μ-O)(μ-I)(μ-O2CCH3)I2(THF)4][MoOI4(THF)] (THF = tetrahydrofuran)

The interaction between Mo₂(O₂CCH₃)₄, Me₃SiI and I₂ in THF resulted in oxygen abstraction from the solvent and formation of [Mo₂(μ-O)(μ-I)(μ-O₂CCH₃) I₂(THF)₄]⁺[MoOI₄(THF)]⁻ and I---(CH₂)₄---I. The molybdenum complex has been characterized by X-ray diffractometry. Crystal data: triclinic, space group P , a = 13.827(3) Å; b = 15.803(7) Å; c = 9.950(3) Å; = 93.34(4)°; β = 102.40(2)°; γ = 90.09(2)°; V = 2120(2) Å₃; Z = 2; d_calc = 2.559 g cm⁻³; R = 0.0476 (R_w = 0.0613) for 370 parameters and 3938 data with F₀²> 3σ(F₀²). The metal-metal distance in the cation is 2.527(2) Å and indicates a strong interaction. The magnetic behavior is consistent with the assignment of one unpaired electron to the Mo₂⁷⁺ core of the cation and one to the d¹ Mo(V) center of the anion. The interaction between Mo(CO)₆ and I₂ in THF also results in the formation of 1,4-diiodobutane.     

Structural and theoretical studies of Xe(OChF5)2 and [XeOChF5][AsF6] (Ch = Se, Te)

The XeOSeF₅⁺ cation has been synthesized for the first time and characterized in solution by ¹⁹F, ⁷⁷Se and ¹²⁹Xe NMR spectroscopy and in the solid state by X-ray crystallography and Raman spectroscopy with AsF₆⁻ as its counter anion. The X-ray crystal structures of the tellurium analogue and of the Xe(OChF₅)₂ derivatives have also been determined: [XeOChF₅][AsF₆] crystallize in tetragonal systems, P4/n, a=6.1356(1) Å, c=13.8232(2) Å, V=520.383(14) Å³, Z=2 and R₁=0.0453 at −60°C (Te) and a=6.1195(7) Å, c=13.0315(2) Å, V=488.01(8) Å³, Z=2 and R₁=0.0730 at −113°C (Se); Xe(OTeF₅)₂ crystallizes in a monoclinic system, P2₁/c, a=10.289(2) Å, b=9.605(2) Å, c=10.478(2) Å, β=106.599(4)°, V=992.3(3) Å³, Z=4 and R₁=0.0680 at −127°C; Xe(OSeF₅)₂ crystallizes in a triclinic system, , a=8.3859(6) Å, c=12.0355(13) Å, V=732.98(11) Å³, Z=3 and R₁=0.0504 at −45°C. The energy minimized geometries and vibrational frequencies of the XeOChF₅⁺ cations and Xe(OChF₅)₂ were calculated using density functional theory, allowing for definitive assignments of their experimental vibrational spectra.     

Synthesis and crystal structure of a complex bearing interesting structural motifs: [Cu (C4H7N3) H2O (4,4′-Hbpy)]·SO4·NO3

A new complex [Cu (C₄H₇N₃) H₂O (4,4′-Hbpy)]·SO₄·NO₃ was synthesized and X-ray characterized. Elemental analysis, X-ray diffraction and infrared spectroscopy of the complex were performed. The crystal system is orthorhombic. Crystal data: Fw=498.98, spacegroup: P212121. Z=4, a=14.952(3), b=20.491(4), c=6.713 Å. V=2056.7(9) Å. λ(Mo-K)=0.71070 Å. μ=12.18 cm⁻¹, D_calc=1.66 g/cm³, F₀₀₀=1032.00, R=0.062, Rw=0.087. X-ray analysis illustrated that 4,4′-bpy is mono-protonated and that there are two kinds of anions in one molecule, which give rise to the hydrogen interaction between the molecules in the crystal. Then an extended three-dimensional network is formed along the hydrogen bonds and π–π bonds between the pyridine rings.     

Structural studies on polynuclear osmium carbonyl hydrides XXXIV. Elucidation of the molecular structure from a crystal structure of disordered (μ-H)5Os3Re(CO)12

The complex (μ-H)₅Os₃Re(CO)₁₂ crystallizes in the centrosymmetric hexagonal space group P6₃/m (C²_6h; No. 176) with a 19.087(5), c 10.963(1) Å, V 3459(3) ų, and Z = 6. Diffraction data were collected on a Syntex P2₁ automated four-circle diffractometer (Mo-K radiation, 2θ = 4.5–45.0°) and the structure was refined to R_F = 7.9% for all 1480 unique reflections (R_F = 5.4% for those 1007 data with ¦F_o¦ > 6σ(¦F_o¦)). The molecule contains a tetrahedral core of metal atoms each associated with three terminal carbonyl ligands. It is bisected by a crystallographic mirror plane. Although the hydride ligands were not located, a consideration of metal-metal distances allows the distinction between osmium and rhenium atoms and suggests that the structure is subject to a subtle form of two-fold disorder.     

New cyclic tellurides. Synthesis, reaction and ligand properties of 2,2,6,6-tetramethyl-1-oxa-4-tellura-2,6-disilacyclohexane (C6H16OSi2Te). X-Ray structure determination of C6H16OSi2TeI2

A new tellurium-containing heterocyclic compound, 2,2,6,6-tetramethyl-1-oxa-4-tellura-2,6-disilacyclohexane (C₆H₁₆OSi₂Te) (1), has been prepared by treatment of 1,3-bis(chloromethyl)-1,1,3,3-tetramethyldisiloxane with sodium telluride. Mononuclear and dinuclear palladium complexes of this telluride have been prepared by the reaction of 1 with PdCl₂(PhCN)₂ and Na₂PdCl₄, respectively. The following new derivatives of 1 have also been produced: C₆H₁₆OSi₂TeI₂ (2), C₆H₁₆OSi₂TeBr₂, C₆H₁₆OSi₂TeCl₂, C₆H₁₆OSi₂Te(CH₃)I, and C₆H₁₆OSi₂Te(CH₂Ph)Br. IR, ¹H and ¹³C NMR and mass spectral data of these new compounds are reported and discussed. ¹H NMR studies revealed that in CDCl₃ solution both telluronium salts reductively eliminate alkyl halide. The crystal structure of compound 2 has been determined by X-ray diffraction. The compound crystallizes in the monoclinic space group, P2₁/c, with four molecules in a unit cell of dimension a 12.960(3), b 8.846(2), c 13.754(4) Å, β 92.44(2)°, R = 0.049, and R_w = 0.067 for 3599 unique reflections with |F₀| > 3σ(F₀). The compound forms a six-membered ring of a slightly displaced boat type. The geometry about the Te atom is pseudo-octahedral, with two carbon atoms (Te-C = 2.156(7) and 2.137(6) Å) and two iodine atoms of the neighbouring molecules (weak intermolecular bonds, Te · I = 3.769 and 3.806 Å) in the equatorial positions and two iodine atoms (Te-I = 2.909(1) and 2.913(1) Å) in the axial positions.     

Syntheses and structural determination of nine-coordinate K3[Nd(nta)2(H2O)]·6H2O and K3[Er(nta)2(H2O)]·5H2O

The syntheses and structural determination of Nd^III and Er^III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K₃[Nd^III(nta)₂(H₂O)]·6H₂O complex belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm³, Z=8, M=763.89, D_c=1.930 g cm⁻³, μ=2.535 mm⁻¹ and F(000)=3048. The final R₁ and wR₁ are 0.0390 and 0.0703 for 4501 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd^IIIN₂O₇ part in the [Nd^III(nta)₂(H₂O)]³⁻ complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly. The crystal of the K₃[Er^III(nta)₂(H₂O)]·5H₂O complex also belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm³, Z=8, M=768.89, D_c=1.987 g cm⁻³, μ=3.833 mm⁻¹ and F(000)=3032. The final R₁ and wR₁ are 0.0321 and 0.0671 for 4445 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er^IIIN₂O₇ part in the [Er^III(nta)₂(H₂O)]³⁻ complex anion has the same structure as Nd^IIIN₂O₇ part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly.     

Preparation and crystal structure of a 1:1 inclusion compound of 1,4,11,14-tetramethoxy-dibenzo[b,n]tetraphenylene with pyridine

The new host 1,4,11,14-tetramethoxy-dibenzo[b,n]tetraphenylene forms a 1:1 inclusion compound with pyridine, in which a pair of centrosymmetrically-related guest species are enclosed in the cage surrounded by six host molecules. C₃₆H₂₈O₄·C₅H₅N, F_W=603.68, triclinic, space group P-1, a=11.796(2), b=16.075(3), c=9.004(2) Å; =98.39(3)°, β=90.01(3)°, γ=108.19(3)°, V=1602.8(5) Å³, Z=2, F(000)=636, D_c=1.251 g/cm³, μ=0.080 mm⁻¹. The final R indices [I>2σ(I)] R₁=0.0759, wR₂=0.1970 for 5623 MoK observed data.     

Tetrahedral versus square planar arrangement of cyclopentadienyl ligands in bimetallic organosamarium complexes. X-ray crystal structure of [(C5H4Me)2(THF)Sm(μ-Cl)]2

The effects of cyclopentadienyl ring size on the geometry of bimetallic organosamarium complexes have been studied by comparing the X-ray crystal structure of [(C₅H₄Me)₂(THF)Sm(μ-Cl)]₂, prepared from KC₅H₄Me and SmCl₃ in THF, with C₅Me₅ analogs. The complex crystallizes from THF at −30°C in space group Pbcn with a = 20.312(5), b = 9.626(2), c = 16.225(3) Å, V = 3172.5(12) ų and D_calc = 1.74 g cm⁻³ for Z = 4. Least-squares refinement of the model based on 1759 reflections [|F_o| > 2.0σ(|F_o|)] converged to a final R_F = 5.0%. The complex adopts a geometry which has a molecular two-fold rotation axis perpendicular to the Sm₂Cl₂ plane and a crystallographic inversion center. Hence, both methyl groups of each (C₅H₄Me)₂Sm unit are located on the side opposite of the THF ligands, which are trans to each other, and the four C₅H₄Me ring centroids define a square plane. The Sm---Cl distances are 2.759(3) and 2.819(3) Å.     

Studies of π-bonding perturbation in the tungsten-nitrogen multiple bond of isopropylimido tungsten(VI) complexes: The crystal and molecular structures of [W(NCHMe2)Cl4]2·C6H6 and [W(NCHMe2)Cl5][NEt4]

¹³C NMR chemical shift data for the -carbon (δ) of a variety of tungsten isopropylimido complexes indicate that the extent to which the nitrogen lone pair participates in multiple bonding to tungsten depends on the form of the complex and the ligands involved. The structures of [W(NCHMe₂)Cl₄]₂·C₆H₆ (1a) and [W(NCHMe₂)Cl₅][NEt₄] (7) which show widely different δ values, have been determined by single-crystal X-ray diffraction methods. Crytals of 1a are triclinic space group P , with a = 6.394(2), b = 8.890(3), c = 11.205(2) Å and = 109.95(2)°, β = 98.91(2)°, γ = 93.96(2)°; crystals of 7 are orthorhombic, space group Pnma, with a = 13.667(5), b = 15.152(2), c = 9.432(2) Å. Both structures were solved by Patterson and Fourier methods and refined to an R value of 0.050 for 1325 observed data of 1a and to an R value of 0.050 for the 1157 observed data of 7. Complex 1a is dimeric with a W---N bond length of 1.697(12) Å and complex 7 is monomeric with a longer W---N bond length of 1.763(16) Å. Comparison of the W---Cl bond lengths and correlations with π-bonding to make an 18-electron count, indicates that the W---N bond lengths differ in the two complexes as a result of overall π-bonding requirements.     

Concerning the crystal structure of BrF3·AuF3

Crystals of the adduct, BrF₃·AuF₃, are monoclinic, with: a=5.356(4) Å, b=5.766(4) Å, c=8.649(3) Å, β=101.39(4)°, V=261.8(5) Å³, z=2, D_c=4.96 g/cm³. An ordered structure in P2₁ was found, but is of low precision (R₁=0.082) because of crystal deformation. The structure has planar BrF₄ units sharing F ligands cis with planar AuF₄ groups, each AuF₄ being similarly linked to two BrF₄. This generates a ribbon, creased at the bridging F along y, the gold on one side of the crease, the bromine on the other. Such ribbons are stacked parallel along y, with nearest neighbors related by twofold screw axes. This sandwiches each AuF₄ strip of a ribbon symmetrically between like strips. These contacts between the Au-strips bring up, to each Au-atom, two “non-bridging Au–F ligands” of each of the two neighboring strips, to give eight coordination in F. The bromine side of the creased ribbon is unsymmetrically sandwiched between a screw-axis related relative, and the edge of a Au-containing strip oriented almost perpendicular to it. This brings two non-bridging F of the nearest-strip BrF₄ and two non-bridging F of the AuF₄ strip into the secondary cordination sphere of the Br atom. Raman spectra of the BrF₃·AuF₃, molecular BrF₃, and polymeric AuF₃ suggest that the Br–F and Au–F stretching vibrations of BrF₃·AuF₃ are shifted slightly from those of the parent BrF₃ and AuF₃, and indicate some BrF₂⁺AuF₄⁻ character.     

Structures of propionaldehyde, butyraldehyde, and pivalaldehyde complexes of the chiral rhenium fragment [(η-C5H5)Re(NO)(PPh3)]

The crystal structures of propionaldehyde complex (RS,SR)-(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₃)]⁺ PF₆⁻ (1b⁺ PF₆^s−; monoclinic, P2₁/c (No. 14), a = 10.166 (1) Å, b = 18.316(1) Å, c = 14.872(2) Å, β = 100.51(1)°, Z = 4) and butyraldehyde complex (RS,SR)-[(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₂CH₃)]⁺ PF₆⁻ (1c⁺PF₆⁻; monoclinic, P2₁/a (No. 14), a = 14.851(1) Å, b = 18.623(3) Å, c = 10.026(2) Å, β = 102.95(1)°, Z = 4) have been determined at 22°C and −125°C, respectively. These exhibit C O bond lengths (1.35(1), 1.338(5) Å) that are intermediate between those of propionaldehyde (1.209(4) Å) and 1-propanol (1.41 Å). Other geometric features are analyzed. Reaction of [(η⁵-C₅H₅)Re(NO)(PPh₃)(ClCH₂Cl)]⁺ BF₄⁻ and pivalaldehyde gives [(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHC(CH₃)₃)]⁺BF₄⁻ (81%), the spectroscopic properties of which establish a π C O binding mode.     

Synthesis and characterisation of the methylene-inserted mixed-chalcogenide compounds Fe2(CO)6(μ-SeCH2Te) and Fe2(CO)6(μ-SCH2Te)

The methylene-bridged, mixed-chalogen compounds Fe₂(CO)₆(μ-SeCH₂Te) (1) and Fe₂(CO)₆(μ-SCH₂Te) (3) have been synthesised from the room temperature reaction of diazomethane with Fe₂(CO)₆(μ-SeTe) and Fe₂(CO)₆(μ-STe), respectively. Compounds 1 and 3 have been characterised by IR, ¹H, ¹³C, ⁷⁷Se and ¹²⁵Te NMR spectroscopy. The structure of 1 has been elucidated by X-ray crystallography. The crystalsare monoclinic,space group P2₁/n, A = 6.695(2), B = 13.993(5), C = 14.007(4)Å, β = 103.03(2)°, V = 1278(7) ų, Z = 4, D_c = 2.599 g cm⁻³ and R = 0.030 (R_w = 0.047).     

Hydrothermal synthesis and structure of one-dimensional Co(dien)2(VO3)3·(H2O) (dien=diethylenetriamine)

One-dimensional Co(dien)₂(VO₃)₃·(H₂O) was prepared from the hydrothermal reaction of NH₄VO₃, Co₂O₃, diethylenetriamine (dien) and H₂O at 130 °C. The compound crystallizes in the monoclinic system, space group P2₁/c with a=16.1581(6) Å, b=8.7006(3) Å, c=13.9893(4) Å, β=103.1483(11)°, V=1915.13(11) Å³, Z=4, and R₁=0.0268 for 3060 observed reflections. Single crystal X-ray diffraction revealed that the structure is composed of infinite one-dimensional chains formed by corner-sharing VO₄ tetrahedra with Co(dien)³⁺ complex cations and crystallization water molecules occupying the interchain positions, which are held together to a three-dimensional network via extensive hydrogen-bonding interactions. The compound, with a new zig-zag conformation of metavanadate chains, is the first example of vanadium oxides incorporating trivalent transition metal coordination groups. Other characterizations by elemental analysis, IR and thermal analysis are also described.     

Preparation and structure of a ruthenium dicarbonyl derivative of the P2N4S2 ring

The reaction of Ru(CO)₄(C₂H₄) or Ru(CO)₅ with 1,5-Ph₄P₂N₄S₂ in CH₂Cl₂/hexane at 23°C produces the dimer [Ru(CO)₂(Ph₄ P₂N₄S₂)]₂ (2), which was shown by X-ray crystallography to have a centrosymmetric structure in which the P₂N₄S₂ ring is attached to one ruthenium atom through two (geminal) nitrogen atoms and the remote sulfur atom and serves as a bridge to the other ruthenium atom via the second sulfur atom. Crystals of 2 ·2(CH₂Cl₂) are triclinic, space group P (No. 2), a = 12.901(1) Å, b = 13.072(1) Å, c = 10.123(1) Å, = 100.88(1)°, β = 98.90(1)°, γ = 67.50(1)°, V = 1542.4(3) Å, Z = 1 with final R and R_w values of 0.040 and 0.027, respectively.     

Synthesis, characterization and the unpleasantly disordered crystal structure of Ir(Ome)(CO)(PPh3)2(SO4)

The adducts of O₂ and SO₂ with trans-MeOIr(CO)(PPh₃)₂ are formed in equilibria and have been characterized. Reaction of the SO₂ adduct, Ir(OMe)(SO₂)(CO)(PPh₃)₂ with dioxygen leads to the sulfato complex, Ir(Ome)(CO)(PPh₃)₂(SO₄), the structure of which has been determined. Ir(Ome)(CO)(PPh₃)₂(SO₄) crystallizes in the monoclinic system with a 11.958(2), b 14.163(3), c 12.231(2) Å, β 118.365(12)°, V 1822.7(6) ų and Z = 2. Diffraction data for 2θ = 4.5–45.0° (Mo-K) were collected with a Syntex P2₁ diffractometer and the structure was solved (assuming space group P2₁/m and an unpleasant 2-fold disordered model) and refined to R = 4.8% for all 2512 independent data (R = 3.5% for those 2042 data with ¦F_O¦ > 6σ(¦F¦)). The iridium(III) atom has a distorted octahedral coordination sphere with trans PPh₃ ligands and a cis-chelating bidentate O,O′-SO₄ group; the structure is completed by mutually cis OMe and CO ligands.     

Structure and conformation of 2,3,4-triphenyl-1-oxa-4-azabutadiene

2,3,4-triphenyl-1-oxa-4-azabutadine (C20H15NO) has been studied by X-ray analysis and AM1 molecular orbital methods. It crystallises in the triclinic space group P-1 with a=9.414(3), b=10.479(3), c=8.385(2) Å, =103.31(3)°, β=97.10(3)°, γ=74.09(1)°, V=772.5(4) ų, Z=2, D_c=1.227 gcm⁻³, and μ(MoK)=0.075 mm⁻¹ and F₀₀₀=300. The structure was solved by direct methods and refined to R=0.043 for 2672 reflections [I>2σ(I)]. The conformational analysis of the title compound were investigated by semi-empirical quantum mechanical AM1 calculations. The minimum conformation energies were calculated as a function of the three torsion angles θ₁(O(1)C(7)C(8)N(1)), θ₂(C(8)N(1)C(15)C(16)) and θ₃(C(14)C(9)C(8)N(1)). The results are compared with the X-ray results. C=O and C=N groups are twisted about each other by 95.5(2)°.     

Hydrothermal synthesis and crystal structure of a novel three-dimensional mixed-valence iron coordination polymer [Fe2FeO2(IN)2(ox)] (IN=isonicotinate, OX=oxalate)

A novel three-dimensional (3D) mixed-valence iron coordination polymer [Fe₂^IIIFe^IIO₂(IN)₂(ox)] (IN=isonicotinate, OX=oxalate) (1) has been hydrothermally synthesized by using two different anionic ligands and characterized by elemental analysis, IR spectrum, electron spin resonance (ESR), X-ray photoelectron spectrum (XPS), thermogravimetric analysis (TGA) and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic, space group P2(1)/c with a=5.8774(7) Å, b=18.528(2) Å, c=7.7117(9) Å, V=817.69(17) Å³, Z=2, and R₁=0.0321 (wR₂=0.0777). The Fe(II) and Fe(III) centers in 1 both exhibit a distorted octahedral coordination geometry and are bridged by the IN and oxalate groups into a covalently bonded 3D metal–organic network. TGA showed that the 3D network possesses a good stability up to 291 °C.     

Structural characterization of cyclopentadienyl(duroquinone)cobalt dihydrate

The structure of cyclopentadienyl(duroquinone)cobalt dihydrate, (C₅H₅)Co-[(CH₃)₄C₆O₂]·2H₂O, has been determined by three-dimensional X-ray analysis. The crystal structure consists of discrete cyclopentadienyl(duroquinone)cobalt molecules linked together by a complex network of hydrogen bonds between water molecules and duroquinone oxygen atoms. Each (C₅H₅)Co[(CH₃)₄C₆O₂] molecule consists of a cobalt atom sandwiched between a cyclopentadienyl ring and a duroquinone ring. A detailed comparison of the molecular parameters of this complex with those of closely related complexes is given. Crystallographic evidence that the metal---duroquinone interaction in cyclopentadienyl(duroquinone)cobalt dihydrate is considerably stronger than that in the electronically-equivalent 1,5-cyclooctadiene(duroquinone)nickel complex is given not only by the metal---C(olefin) distances being 0.12 Å (av) shorter in the duroquinone---cobalt complex [viz., 2.104(8) Å vs. 2.222(7) Å] but also by the much greater C_2v-type distortion of the duroquinone ring from the planar D_2h configuration in free duroquinone. The compound crystallizes with two formula species in a triclinic unit cell of symmetry P and reduced cell dimensions á = 8.60 Å, b = 9.00 Å, c = 10.15 Å, = 87° 34′, β = 84° 10′, γ = 73° 44′. Least-squares refinement yielded final unweighted and weighted discrepancy factors of R₁ = 10.8% and R₂ = 12.0%, respectively, for 2481 independent diffraction maxima collected photographically.     

The gas phase structure of tetrakis(trifluoromethylthio)ethene, CF3S)2C=C(SCF3)2

The geometric structure of (CF₃S)₂C=C(SCF₃)₂ in the vapour phase was determined by electron diffraction. The molecule possesses D₂ symmetry with the S---CF₃ bonds oriented perpendicular to the ethene plane, in alternating directions up-down-up-down. The following skeletal geometric parameters were obtained (r_a distances and angles, experimental uncertainties are 3σ values): C=C = 1.34Å (ass.), C(sp²---S = 1.761(5)Å, S---C(sp³) = 1.832(5)Å, S---C---C = 119.6(4)°, C---S---C = 100.6(13)°, and ø(C=C---S---C) = 90.9(11)°. The gas phase conformation differs considerably from the crystal structure, where the molecule possesses C_i symmetry and the CF₃ groups, which are bonded to cis-standing sulfur atoms, lie on the same side of the ethene plane with dihedral angles ø(C=C---S---C) of 117° and 127°.