Synthesis and application of diphenylbis (3,5-dimethylpyrazol-1-yl)methane to form η-arene complexes of molybdenum

The neutral nitrogen-bidentate ligand, diphenylbis(3,5-dimethylpyrazol-1-yl)methane, Ph₂CPz′₂, can readily be obtained by the reaction of Ph₂CCl₂ with excess HPz′ in a mixed-solvent system of toluene and triethylamine. It reacts with [Mo(CO)₆] in 1,2-dimethoxyethane to give the η²-arene complex, [Mo(Ph₂CPz′₂)(CO)₃] (1). This η²-ligation appears to stabilize the coordination of Ph₂CPz′ ₂ in forming [Mo(Ph₂CPz′₂)(CO)₂(N₂C₆H₄NO₂-p)][BPh₄] (2) and [Mo(Ph₂CPz′₂)(CO)₂(N₂Ph)] [BF₄] (3) from the reaction of 1 with the appropriate diazonium salt but the stabilization seems not strong enough when [Mo{P(OMe)₃} ₃(CO)₃] is formed from the reaction of 1 with P(OMe)₃. The solid-state structures of 1 and 3 have been determined by X-ray crystallography: 1-CH₂Cl₂, monoclinic, P2₁/n, a = 11.814(3), b = 11.7929(12), c = 19.46 0(6) Å, β = 95.605(24)°, V = 2698.2(11) ų, Z = 4, D_calc = 1.530 g/cm³ , R = 0.044, R_w = 0.036 based on 3218 reflections with I > 2σ(I); 2 (3)-1/2 hexane-1/2 CH₃OH-1/2 H₂O-1 CH₂Cl₂, monoclinic, C2/c, a = 41.766(10), b = 20.518(4), c = 16.784(3) Å, β = 101.871(18)°, V = 14076(5) ų, Z = 8, D_calc = 1.457 g/cm³, R = 0.064, R_w = 0.059 based on 5865 reflections with I > 2σ(I). Two independent cations were found in the asymmetric unit of the crystals of 3. The average distance between the Mo and the two η²-ligated carbon atoms is 2.574 Å in 1 and 2.581 and 2.608 Å in 3. The unfavourable disposition of the η²-phenyl group with respect to the metal centre in 3 and the rigidity of the η²-arene ligation excludes the possibility of any appreciable agostic C---H → Mo interaction.     

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.     

Synthesis, crystal structure and third-order non-linear optical property of heterobimetallic cluster compound [MoOICu3S3(2,2′-bipy)2]

Nest-shaped cluster [MoOICu₃S₃(2,2′-bipy)₂] (1) was synthesized by the treatment of (NH₄)₂MoS₄, CuI, (n-Bu)₄NI, and 2,2′-bipyridine (2,2′-bipy) through a solid-state reaction. It crystallizes in monoclinic space group P2₁/n, a=9.591(2) Å, b=14.820(3) Å, c=17.951(4) Å, β=91.98(2)°, V=2549.9(10) ų, and Z=4. The nest-shaped cluster was obtained for the first time with a neutral skeleton containing 2,2′-bipy ligand. The non-linear optical (NLO) property of [MoOICu₃S₃(2,2′-bipy)₂] in DMF solution was measured by using a Z-scan technique with 15 ns and 532 nm laser pulses. The cluster has large third-order NLO absorption and the third-order NLO refraction, its ₂ and n₂ values were calculated as 6.2×10⁻¹⁰ and −3.8×10⁻¹⁷ m² W⁻¹ in a 3.7×10⁻⁴ M DMF solution.     

Formation and structure of [Co{Ph2PN(Bu)PPh2-P,P′}2(CO)][Co)(CO)4] - a cage molecule-pair or an ion-pair complex?

The strong π-acid ligand Ph₂PN(ⁱBu)PPh₂ reacts with Co₂(CO)_S (1:1) to give Co₂[μ-Ph₂PN(ⁱBu)PPh₂] (μ-CO)₂(CO)₄ (1); however, when the ratio is 2:1 a novel species [Co{Ph₂PN(ⁱBu)PPh₂-P,P′}₂(CO)][Co(CO)₄] (2) has been obtained. Crystal data for 2: M_r = 1140.83; triclinic, space group P , a = 12.330(2), b = 13.340(2), c = 18.122(3) Å, = 86.63(1), β = 80.75(1), γ = 84.24(1)°, V = 2924 ų, Z = 2; R = 0.060 for 3711 reflections having I 3σ(I). The results of X-ray diffraction, ESR, variable-temperature magnetic susceptibility, conductivity, and XPS analysis support that the species 2 is a d⁹-d⁹ cage molecule-pair. The mechanism for the formation of the species 2 has been investigated initially by ³¹P NMR.     

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.     

Anionic derivatives of pentafluoro-λ-sulfanyl (fluorosulfonyl) acetic acid esters

New ester salts [R₃NH]⁺[F₅SC(SO₂F)C(O)OR′]⁻ where RH, CH₃CH₂ and R′CH₃,(CH₃)₂CH have been prepared from corresponding esters and amines. The sodiumsalt Na[F₅SC(SO₂F)C(O)OCH(CH₃)₂] was used to prepare the following -substitutedderivatives: SF₅CX(SO₂F)C(O)OCH(CH₃)₂, XBr, Cl. The crystal structure of[(C₂H₅)₃NH]⁺[F₅SC(SO₂F)C(O)OCH₃]⁻ was determined and is monoclinic: P2₁/n;a=8.758(2) Å, b=9.645(2) Å and c=19.167(4) Å; β=97.92(3)°; V=1603.6 ų; Z=4.     

Group 4 metallacarboranes of constrained geometries derived from B(cage)- and C(cage)-silylamido-substituted carborane ligands: a synthetic and structural investigation

The reactions of RNHSi(Me)₂Cl (1, R=t-Bu; 2, R=2,6-(Me₂CH)₂C₆H₃) with the carborane ligands, nido-1-Na(C₄H₈O)-2,3-(SiMe₃)₂-2,3-C₂B₄H₅ (3) and Li[closo-1-R′-1,2-C₂B₁₀H₁₀] (4), produced two kinds of neutral ligand precursors, nido-5-[Si(Me)₂N(H)R]-2,3-(SiMe₃)₂-2,3-C₂B₄H₅, (5, R=t-Bu) and closo-1-R′-2-[Si(Me)₂N(H)R]-1,2-C₂B₁₀H₁₀ (6, R=t-Bu, R′=Ph; 7, R=2,6-(Me₂CH)₂C₆H₃, R′=H), in 85, 92, and 95% yields, respectively. Treatment of closo-2-[Si(Me)₂NH(2,6-(Me₂CH)₂C₆H₃)]-1,2-C₂B₁₀H₁₁ (7) with three equivalents of freshly cut sodium metal in the presence of naphthalene produced the corresponding cage-opened sodium salt of the “carbons apart” carborane trianion, [nido-3-{Si(Me)₂N(2,6-(Me₂CH)₂C₆H₃)}-1,3-C₂B₁₀H₁₁]³⁻ (8) in almost quantitative yield. The reaction of the trianion, 8, with anhydrous MCl₄ (M=Ti and Zr) in 1:1 molar ratio in dry tetrahydrofuran (THF) at −78 °C, resulted in the formation of the corresponding half-sandwich neutral d⁰-metallacarborane, closo-1-M[(Cl)(THF)_n]-2-[1′-η¹σ-N(2,6-(Me₂CH)₂C₆H₃)(Me)₂Si]-2,4-η⁶-C₂B₁₀H₁₁ (M=Ti (9), n=0; M=Zr (10), n=1) in 47 and 36% yields, respectively. All compounds were characterized by elemental analysis, ¹H-, ¹¹B-, and ¹³C-NMR spectra and IR spectra. The carborane ligand, 7, was also characterized by single crystal X-ray diffraction. Compound 7 crystallizes in the monoclinic space group P2₁/c with a=8.2357(19) Å, b=28.686(7) Å, c=9.921(2) Å; β=93.482(4)°; V=2339.5(9) ų, and Z=4. The final refinements of 7 converged at R=0.0736; wR=0.1494; GOF=1.372 for observed reflections.     

Synthesis and molecular structure of the optically active organoaluminium dimer (S)-(—)-(S)-(—)- [(C6H5)CH(CH3)NHA1(CH3)2]2

Reaction of the optically active primary amine (S)-(—)--methylbenzylamine with trimethylaluminium in heptane affords the crystalline organoaluminium dimer (S)-(—)-(S)-(—)-[(C₆H₅)CH(CH₃)NHA1(CH₃)₂]₂. Isolated as large, colourless, extremely air-sensitive prismatic crystals, the title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters a = 8.406(3), b = 15.505(4), c = 17.547(5) Å, V = 2287 ų and p = 1.03 g cm⁻³ for Z = 4. Least-squares refinement based on 1477 observed reflections converged at R = 0.056, R_w = 0.058. Methane was eliminated during the course of the reaction due to cleavage of A1---C and N---H bonds resulting in an asymmetric A1₂N₂ fragment at the core of the organoaluminium dimer. The mean A1---C bond distance in the dimethylaluminium units is 1.930(8), while the mean A1---N bond distance is 1.950(5) Å. Specific rotation ([]_D²⁵ in CH₂C1₂)of the dimer is determined to be - 20.6°.     

Structural and spectral studies of N-2-(pyridyl)-, N-2-(3-, 4-, 5-, and 6-picolyl)- and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenylthioureas

Structures of the following compounds have been obtained: N-(2-pyridyl)-N′-2-thiomethoxyphenylthiourea, PyTu2SMe, monoclinic, P2₁/c, a=11.905(3), b=4.7660(8), c=23,532(6) Å, β=95.993(8)°, V=1327.9(5) ų and Z=4; N-2-(3-picolyl)-N′-2-thiomethoxyphenyl-thiourea, 3PicTu2SeMe, monoclinic, C2/c, a=22.870(5), b=7.564(1), c=16.941(4) Å, β=98.300(6)°, V=2899.9(9) ų and Z=8; N-2-(4-picolyl)-N′-2-thiomethoxyphenylthiourea, 4PicTu2SMe, monoclinic P2₁/a, a=9.44(5), b=18.18(7), c=8.376(12) Å, β=91.62(5)°, V=1437(1) ų and Z=4; N-2-(5-picolyl)-N′-2-thiomethoxyphenylthiourea, 5PicTu2SMe, monoclinic, C2/c, a=21.807(2), b=7.5940(9), c=17.500(2) Å, β=93.267(6)°, V=2893.3(5) ų and Z=8; N-2-(6-picolyl)-N′-2-thiomethoxyphenylthiourea, 6PicTu2SMe, monoclinic, P2₁/c, a=8.499(4), b=7.819(2), c=22.291(8) Å, β=90.73(3)°, V=1481.2(9) ų and Z=4 and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenyl-thiourea, 4,6LutTu2SMe, monoclinic, P2₁/c, a=11.621(1), b=9.324(1), c=14.604(1) Å, β=96.378(4)°, V=1572.4(2) ų and Z=4. Comparisons with other N-2-pyridyl-N′-arylthioureas having substituents in the 2-position of the aryl ring are included.     

Structural, spectral and thermal properties of a polymeric nickel(II) complex containing two-dimensional network

The structure of the complex [Ni(hmt)(NCS)₂(H₂O)₂]_n, assembled by hexamethylenetetramine (hmt) and octahedral Ni(II), is reported. Crystal data: Fw 351.07, a=9.885(10) Å, b=12.06(1) Å, c=12.505(8) Å, β=114.41(4)°, V=1357(1) ų, Z=4, space group=C2/c, T=173 K, λ(Mo−K)=0.71070 Å, ρ_calc=1.718 gcm⁻¹, μ=17.44 cm⁻¹, R=0.099, Rw=0.145. The tetrahedral assembling template effect of the hmt molecule is completed by two coordination bonds and two hydrogen interactions. The UV–vis absorption spectrum of this complex [Ni(hmt)(NCS)₂(H₂O)₂]_n with a two-dimensional network is determined in the range of 5000–35000 cm⁻¹ at room temperature. The observed spectrum is discussed and explained perfectly by the scaling radial theory proposed by us. The two-dimensional structure has no apparent effects on the d–d transitions of the central Ni(II) ion. The IR spectrum and the GT curve of the complex were also measured and clearly reflect its structural properties.     

Dynamic behaviour and X-ray analysis of chiral η-allylpalladium complexes. II

The DANTE technique and NOESY two-dimensional method have been employed to observe the isomerization of the chiral cationic complex [Pd(η³-CH₂CMeCH₂(P-P′)]⁺ (1a), where P-P′ = the chiral chelating ligand (S)(N-diphenylphosphino)(2-diphenylphosphinoxymethyl)pyrrolidine. The rate constant was found to be 0.5 s⁻¹ in CHCl₃ at 295 K and 1.50 s⁻¹ in the presence of added free ligand. In the latter case the epimerization proceeds by a π-σ-π mechanism via the intermediacy of a primary η¹-allylpalladium complex. Although the intermediate was not detected, the NMR findings reveal that it has the allylic terminus η¹-bonded to palladium. The structure of 1a in its PF₆⁻ salt has been determined. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with a 10.029(4) b 19.203(8) c 36.115(6) Å, Z = 8, R = 0.0572 and R_w = 0.0712 for 3716 observed reflections with I > 3σ(I).     

Synthesis and crystal structure of two novel nickel (imidazole) complexes having hydrogen-bonded networks

Two nickel (imidazole) complexes, Ni(im)₆Cl₂·4H₂O (1) and Ni(im)₆(NO₃)₂ (2) (im=imidazole) have been synthesized and characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. 1 crystallizes in the triclinic space group P-1 with a=8.800(6) Å, b=9.081(6) Å, c=10.565(7) Å, =75.058(9)°, β=83.143(8)°, γ=61.722(8)°, V=718.3(8) Å³, Z=1 and R₁ (wR₂)=0.0469 (0.1497). 2 crystallizes in the trigonal space group R-3 with a=12.370(6) Å, b=12.370(6) Å, c=14.782(14) Å, =90.00°, β=90.00°, γ=120.00°, V=1959(2) Å³, Z=3 and R₁ (wR₂)=0.0358 (0.0955). 1 and 2 exhibit different supramolecular network due to their different counter anions and different hydrogen bonding connection. In compound 1, [Ni(im)₆]²⁺ cation and counter anions Cl⁻ alternatively array in an ABAB fashion via N–HCl hydrogen bonding. In compound 2, the plane of each NO₃²⁻ is almost parallel and each NO₃²⁻ connect three different [Ni(im)₆]²⁺ cations via N–HO hydrogen bonding.     

Synthesis and structure of the iron-substituted silylacetylene [(η-C5H5)Fe(CO)2SiMe2C]2 and its cobalt hexacarbonyl derivative [(η-C5H5)Fe(CO)2SiMe2C]2 · Co2(CO)6

A transition metal-substituted silylacetylene [(η⁵-C₅H₅)Fe(CO)₂SiMe₂C]₂, [FpMe₂SiC]₂ (I) was synthesized and characterized spectroscopically and structurally. I crystallized in the monoclinic space group P2₁/n, A = 13.011(3) Å B = 12.912(3) Å, C = 13.175(5) Å, β = 94.95(2). The acetylene linkage is reactive toward Co₂(CO)₈ to form I. Co₂(CO)₆ (II) which was also characterized spectroscopically and by single crystal X-ray diffraction. II crystallized in the orthorhombic space group Pbca, A = 17.64(2) Å, B = 14.225(10) Å, C = 24.49(2) Å.     

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.     

Steric effects of the 2-(diphenylphosphino)pyridine bridging ligand in the synthesis of binuclear palladium(II) complexes

Treatment of [Pd{CH₂C(CH₃)CH₂}(Ph₂PPy)Cl] (Ph₂PPy = 2-(diphenylphosphino)pyridine) with cis-[Pd(^tBuNC)₂Cl₂] in dichloromethane affords the mixed isocyanide-tertiary phosphine complex cis-[Pd(^tBuNC)Ph₂PPy)Cl₂], in which the Ph₂PPy is a monodentate P-donor, and [{Pd[CH₂C(CH₃)CH₂]Cl}₂]. The steric effects of the Ph₂PPy bridging ligand in determining the reaction course is discussed. The complex cis-[Pd(^tBuNC)(Ph₂PPy)Cl₂] was crystallographically characterized: P2₁/n, a = 15.143(2), b = 9.527(1), c = 17.517(4) Å, β = 113.96(1)°, V= 2309.4(7) ų, Z = 4. The final R value was 0.044, R^w= 0.046 for the 3078 reflections with I > 3σ(I).     

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.     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

Studies on organolanthanide complexes : LXIII. Synthesis, spectroscopic and X-ray crystallographic characterization of new early organolanthanide, organoyttrium hydride and organoholmium hydroxide complexes

Organolanthanide chloride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-Cl)]₂ (Ln = La, Pr, Ho and Y) react with excess NaH in THF at 45°C to give the dimeric hydride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-H)]₂, which have been characterized by IR, ¹H NMR, MS and XPS spectroscopy, elemental analyses and X-ray crystallography. [(CH₃OCH₂CH₂C₅H₄)₂Y(μ-H)]₂ crystallizes from THF/n-hexane at −30°C, in the triclinic space group P1 with a = 8.795(2) Å, b = 11.040(1) Å, c = 16.602(2) Å, = 93.73(1)°, β = 91.82(1)°, γ = 94.21(1)°, D_c = 1.393 gcm⁻³ for Z = 2 dimers. However, crystals of [(CH₃OCH₂CH₂C₅H₄)₂Ho(μ-OH)]₂ were obtained by recrystallization of holmium hydride in THF/n-hexane at −30°C, in the orthorhombic space group Pbca with a = 11.217(2) Å, b = 15.865(7) Å, c = 17.608(4) Å, D_c = 1.816 gcm⁻³ for Z = 4 dimers. In the complexes of yttrium and holmium, each Ln atom of the dimers is coordinated by two substituted cyclopentadienyl ligands, one oxygen atom and two hydrogen atoms (for the Y atom) or two hydroxyl groups (for the Ho atom) to form a distorted trigonal bipyramid if the C(η⁵)-bonded cyclopentadienyl is regarded as occupying a single polyhedral vertex.     

Synthesis and crystal structure of a novel mixed valence tri-iron complex salt: [hexakis(thiazole)iron(II)][μ-oxo- bis(trichloroiron(III))]

The title compound, [Fe(tz)₆][Fe₂OCl₆] (1) (tz = thiazole) has been synthesized under argon by the reaction of anhydrous FeCl₃ with thiazole in ethanol. 1 crystallises in the cubic space group (no. 205) with a = 15.001(5) Å, V = 3375(2) ų, Z = 4, R = 0.061 and R_w = 0.073. 1 consists of a face-centered cubic array of [Fe(tz)₆]² cations, with the oxo-bridged [Fe₂OCl₆]²⁻ anion occupying the cell and edge centres.     

Tris-chelate complexes with chiral ligands: In search of diastereoisomeric selectivity with remote stereogenic centres

The chiral ligands, 4,4′-bis{(1S,2R,4S)-(−)-bornyloxy}-2,2′-bipyridine, (1S,2R,4S)-1, and 4,4′-bis{(1R,2S,4R)-(+)-bornyloxy}-2,2′-bipyridine, (1R,2S,4R)-1, have been prepared and characterized by spectroscopic techniques and, for (1S,2R,4S)-1, by single crystal X-ray diffraction. Despite the use of enantiomerically pure ligands, the formation of the complexes [Fe((1S,2R,4S)-1)₃]²⁺, [Ru((1S,2R,4S)-1)₃]²⁺, [Ru((1S,2R,4S)-1)(bpy)₂]²⁺ and [Ru((1R,2S,4R)-1)(bpy)₂]²⁺ proceeds without preference for either the Δ or Λ-diastereoisomers.