Structure and properties of a novel OH bridged dimetal helical complex with 6,6-dimethyl-2,2′:6′,2″:6″,2:6,2-quinquepyridine ligand

A new monohelical OH⁻ bridged dinuclear complex [Zn₂(dmqpy)(OOCCH₃)₂(μ-OH)][ClO₄] · 0.5EtOH, where dmqpy is 6,6-dimethyl-2,2′:6′,2″:6″,2:6,2-quinquepyridine, has been synthesized and characterized by X-ray crystallography: monoclinic, space group P2₁/c, a=13.670(1), b=14.751(1), c=16.782(1) Å, β=96.59(1)°, U=3361.7(4) ų, Z=4, R=0.0601. Two Zn(II) ions are in different coordination modes, one is five-coordinate with a N₃O₂ donor set and the other is N₂O₂ four-coordinate with a distorted tetrahedral geometry, and the zinc ions are bridged by a hydroxyl group. The presence of the OH⁻ bridge is further confirmed by electrospray mass and infrared spectroscopies. The solution properties of the complex were investigated by ¹H NMR spectroscopy. The results of NMR indicate that the complex has higher symmetry in solution than in the solid state.     

Synthesis and magnetic properties of bis(μ-hydroxo)bis[(2,2 ′-bipyridyl)copper(II)] squarate. Crystal structure of bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] squarate tetrahydrate

The compound [Cu₂(bipy)₂(OH)₂](C₄O₄)·5.5H₂O, where bipy and C₄O₄²⁻ correspond to 2,2′-bipyridyl and squarate (dianion of 3,4-dihydroxy-3-cyclo- butene-1,3-dione) respectively, has been synthesized. Its magnetic properties have been investigated in the 2–300 K temperature range. The ground state is a spin-triplet state, with a singlet-triplet separation of 145 cm⁻¹. The EPR powder spectrum confirms the nature of the ground state.Well-formed single crystals of the tetrahydrate, [Cu₂(bipy)₂(OH)₂](C₄O₄)·4H₂O, were grown from aqueous solutions and characterized by X-ray diffraction. The system is triclinic, space group P , with a = 9.022(2), b = 9.040(2), c = 8.409(2) Å, α = 103.51(2), β = 103.42(3), γ = 103.37(2)°, V = 642.9(3) ų, Z = 1, D_x = 1.699 g cm⁻³, μ(Mo Kα) = 17.208 cm⁻¹, F(000) = 336 and T= 295 K. A total of 2251 data were collected over the range 1θ25°; of these, 1993 (independent and with I3σ(I)) were used in the structural analysis. The final R and R_w residuals were 0.034 and 0.038 respectively. The structure contains squarato-O¹, O³-bridged bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] units forming zigzag one-dimensional chains. Each copper atom is in a square-pyramidal environment with the two nitrogen atoms of 2,2′-bipyridyl and the two oxygen atoms of the hydroxo groups building the basal plane and another oxygen atom of the squarate lying in the apical position.The magnetic properties are discussed in the light of spectral and structural data and compared with the reported ones for other bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] complexes.     

Conformational properties of Eu(III) complexes of 3,3′; 5,3″-polymethylene bridged derivatives of 2,2′; 6,2″-terpyridine

The complex [Eu(tpy)₃](ClO₄)₃ where TPY=2,2′; 6,2″-terpyridine, has been prepared and reexamined. The complex appears to be stable in acetonitrile solution with respect to decomplexation of the ligands but the addition of water does cause partial replacement of tpy. Analogous complexes have been prepared with 3,3′; 5,3″-polymethylene bridged derivatives of tpy having two or three carbons in the bridge. The bridging enforces a cisoid geometry of the ligand and prohibits its replacement by added water. An X-ray determination was carried out for [Eu(3b)₃](ClO₄)₃, where 3b=3,3′; 5,3″-dimethylene tpy, which crystallizes in the monoclinic space group P2₁/c with a=11.908(4), b=15.768(5), c=29.513(9) Å, β=93.60(2)°, μ=13.5 cm⁻¹ and Z=4. The complex forms a tricapped trigonal prism with each of the ligands adopting the same dl conformation. Variable temperature NMR analysis of the bridged ligand complexes indicates that conformational inversion of the bound ligand is not a concerted process and barriers for inversion of individual methylene units can be estimated from coalescence of the signals from the geminal methylene protons. The luminescence properties of the bridged tpy complexes are similar to the parent unbridged system.     

Synthesis of [Tl4Se16]: a novel tetranuclear Tl polyselenide

(Ph₄P)₄[Tl₄Se₁₆] was prepared hydrothermally in a sealed pyrex tube by the reaction of TlCl, K₂Se₄ and Ph₄PCl in a 1:1:1 molar ratio at 110 °C for one day. The red crystals were obtained in 50% yield. Crystals of (Ph₄P)₄[Tl₄Se₁₆]: triclinic P (No. 2), Z=1, a=12.054(9), b=19.450(10), c=11.799(6) Å, α=104.63(4), β=98.86(6), γ=101.99(6)° and V=2555(3) ų at 23 °C, 2θ_max=40.0°, μ=120.7 cm⁻¹, D_calc=2.23. The structure was solved by direct methods. Number of data collected: 5206. Number of unique data having F_o²>3σ(F_o²): 1723. Final R=0.075 and R_w=0.089. [Tl₄Se₁₆]⁴⁻ consists of four, almost already linearly arranged, tetrahedral thallium centers which are coordinated by two chelating Se₄²⁻, two bridging Se₂²⁻ and four bridging Se²⁻ ligands. [Tl₄Se₁₆]⁴⁻ sits on an inversion center and possesses a central {Tl₂Se₂}²⁺ planar core. The Tl(1)–Tl(1)′ distance in this core is 3.583(6) Å. These two thallium atoms are then each linked to two cyclic Tl(Se₄) fragments via bridging Se₂²⁻ and Se²⁻ ligands forming Tl₂Se(Se₂) five-membered rings.     

3-(1′,1′-Dimethylbutyl)-1-deoxy-Δ-THC and related compounds: synthesis of selective ligands for the CB2 receptor

The synthesis and pharmacology of 15 1-deoxy-Δ⁸-THC analogues, several of which have high affinity for the CB₂ receptor, are described. The deoxy cannabinoids include 1-deoxy-11-hydroxy-Δ⁸-THC (5), 1-deoxy-Δ⁸-THC (6), 1-deoxy-3-butyl-Δ⁸-THC (7), 1-deoxy-3-hexyl-Δ⁸-THC (8) and a series of 3-(1′,1′-dimethylalkyl)-1-deoxy-Δ⁸-THC analogues (2, n=0–4, 6, 7, where n=the number of carbon atoms in the side chain−2). Three derivatives (17–19) of deoxynabilone (16) were also prepared. The affinities of each compound for the CB₁ and CB₂ receptors were determined employing previously described procedures. Five of the 3-(1′,1′-dimethylalkyl)-1-deoxy-Δ⁸-THC analogues (2, n=1–5) have high affinity (K_i=<20 nM) for the CB₂ receptor. Four of them (2, n=1–4) also have little affinity for the CB₁ receptor (K_i=>295 nM). 3-(1′,1′-Dimethylbutyl)-1-deoxy-Δ⁸-THC (2, n=2) has very high affinity for the CB₂ receptor (K_i=3.4±1.0 nM) and little affinity for the CB₁ receptor (K_i=677±132 nM).

Scheme 3. (a) (C₆H₅)₃PCH₃⁺ Br⁻, n-BuLi/THF, 65°C; (b) LiAlH₄/THF, 25°C; (c) KBH(sec-Bu)₃/THF, −78 to 25°C then H₂O₂/NaOH.     

Tetrachloroplatinate(II) and hexachloroplatinate(IV) salts of N,N,N′,N′-tetramethylethylenediammonium: significant differences in the conformation of the cation, as shown by infrared and x-ray diffraction data

The structures of (H₂tmen)[PtCl₄], (1), (H₂tmen = N,N,N′,N′-tetramethylethylenediammonium), [triclinic, P ; A = 7.344(3), B = 8.345(3), C = 6.216(2) Å, α = 84.53(3), β = 109.22(3), γ = 69.43(3)°, Z = 1] and (H₂tmen)[PtCl₆], (2), [monoclinic, P2₁/a; A = 14.409(4), B = 12.736(7), C = 8.601(3) Å, β = 99.58(3)°, Z = 4] were determined from diffractometric data by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.027 and 0.039 for (1) and (2) respectively. In both cases the anions and cations are joined in polymeric chains through hydrogen bonds involving the protonated nitrogens and the co-ordinated chlorine atoms. The square-planar [PtCl₄]²⁻ and octahedral [PtCl₆]²⁻ anions are centrosymmetric; the H₂tmen²⁺ cations are centrosymmetric in (1) with a N-C-C-N dihedral angle of exactly 180°, while in (2) the dihedral angle is 166°. The different symmetry of the organic moieties/C_i and C₁ in (1) and (2) respectively] results in a different i.r. spectrum which is more complex the lower the symmetry; moreover the spectrum of a KBr pellet of (2) changes with time, finally resembling that of (1) and of the (H₂tmen)Cl₂ salt.     

Synthesis and crystal structure of the MgCl2(CH3COOC2H5)2· (CH3COOC2H5) adduct

The reaction of α-MgCl₂ with boiling ethyl acetate affords MgCI₂(CH₃COOC₂H₅)₂· (CH₃COOC₂H₅), which is obtained as crystals suitable for X-ray analysis only from the mother liquor. M=315.5, orthorhombic, space group P2₁22₁ (No. 18), a=25.077(3), b=8.616(1), c=7.345(1) Å, V=1587.0(3) ų, Z=4, D_x=1.32 g cm⁻³,λ A(Mo Kα)=0.71069 Å, μ=4.17 cm⁻¹, F(000)=664, T=298 K, observed reflections: 1667, R=0.059 and R_w=0.069. The structure is composed of polymeric chains of MgCl₂(CH₃COOC₂H₅₎₂ and the ethyl acetate molecules occupy a mutually trans position.     

The crystal and molecular structure of 1,6-anhydro-β-d-mannopyranose

The crystal structure of 1,6-anhydro-β-d-mannopyranose, C₆H₁₀O₅, is orthorhombic, P2₁2₁2₁, with a = 10.971(2), b = 13.935(3), c = 9.012(1) Å, V = 1377.76 »³ (MoKα, λ = 0.7107 Å), Z = 8, D_x = 1.563 M.gm⁻³, D_m = 1.565 M.gm⁻³. the structure was solved by MULTAN and refined to R(F) = 0.043 for 2355 reflections. The two symmetry-independent molecules in the unit cell have similar conformations, except for the orientation of one of the three hydroxyl groups. The conformation of the pyranose rings is ¹C₄ distorted towards E_o, and that of the anhydro rings is E. There are significant differences between the two molecules in two of the four C---O bond-lengths. These occur where there are important differences in the hydrogen-bonding environment of the oxygen atoms. The molecules are hydrogen-bonded by three linear and three bifurcated O---H···O interactions which form four-membered loops linked into infinite chains. Empirical force-field calculations with MMI-CARB reproduced the geometry of the molecules within the variations observed experimentally between the two molecules, except for a C---O bond in one of the molecules. The effect of excluding the anomeric effect from the theoretical calculations was not significant. Calculations for an intramolecularly hydrogen-bonded molecule were also carried out as a model for the molecules in a non-polar solvent.     

Synthesis and structure of an organosamarium aryloxide complex, (C5 Me5)2 Sm(OC6HMe4-2,3,5,6)

Bis(pentamethylcyclopentadienyl)samarium bis- (tetrahydrofuranate), (C₅Me₅)₂Sm(THF)₂, reacts with 2,3,5,6-tetramethylphenol in toluene to yield (C₅Me₅)₂Sm(OC₆HMe₄-2,3,5,6). The compound crystallizes in the space group P2₁/c with a = 8.725(3) Å, b=18.821(6) Å, c=18.461(6) Å, β= 111.17(2)°, V = 2827(2) ų and D_c=1.340 g cm⁻³ for Z = 4. Molecules of the aryloxide complex are monomeric and exhibit a bent metallocene structure with a nearly linear Sm---O---C(aryloxide) linkage: Sm---O = 2.13(1) Å, O---C = 1.29(2) Å, and Sm---O---C = 172.3(13)°. Reaction of the samarium complex with phenyllithium produces the previously- characterized species (C₅Me₅)₂Sm(C₆H₅)(THF).     

Heterocyclic compounds containing antimony 1. Synthesis, physicochemical properties, crystal and molecular structure of 2-(β-hydroxyethylthio) 1,3,2-oxathiastibolane

The compound (HOCH₂CH₂S) ) (1) has been prepared by the reaction of antimony(III) isopropoxide and 2-mercaptoethanol in a 1:2 molar ratio. Reaction of 1 with MOCH₃ (where M = Li, Na and K) yields bimetallic products of the type, M[(OCH₂CH₂S) )]. All these derivatives have been characterized by elemental analysis, IR, NMR (¹H and ¹³C) spectra and molar conductivity measurements. Crystals of 1 are triclinic, space group P , with a = 6.449(2), b = 10.285(2), c = 13.494(1) Å, α = 78.08(1), β = 75.99(1), γ = 71.54(2)°, V = 815.48 ų, Z = 4, D_calc = 2.239 g cm⁻³, (Mo Kα) λ = 0.7107 Å, μ = 3.55 mm₋₁, F(000) = 528, T = 295 K, final R = 0.0189 for 2344 reflections. One of the two mercaptoethanol moieties in 1 forms a five-membered chelate ring with antimony, Sb(1)---O(11) = 2.023(2) Å and Sb(1)---S(11) = 2.434(1) Å, while the other is bonded through the S atom only, Sb(1)---S(12) = 2.434(1) Å. The angles between these primary bonds with a mean value of 90.2° suggest a basically pyramidal, or pseudo tetrahedral structure if the stereochemically active lone pair is included in the coordination sphere. Two molecules are linked by intermolecular hydrogen bridges. The presence of weak intermolecular secondary bonding, Sb(1)---O(12) = 2.567(3) Å, in the complex indicates that the overall coordination polyhedron is best described in terms of a distorted trigonal bipyramidal arrangement.     

New Crystal Forms of the Motile Major Sperm Protein (MSP) ofAscaris suum

We have obtained two new crystal forms of theAscarismajor sperm protein (MSP) that mediates amoeboid cell motility in nematode sperm. We obtained crystals with C2 symmetry from bacterially expressed α-MSP witha= 216.5 Å,b= 38.6 Å,c= 32.5 Å, γ = 93.1° and also crystals with P2₁symmetry from native β-MSP witha= 63.1 Å,b= 91.7 Å,c= 72.5 Å, γ = 91.3°. A full native data set has been collected for each crystal form using synchrotron radiation. Both crystal forms diffract to 2 Å and are suitable for high-resolution structural investigation.     

The crystal structures of 4,4′-bipyridinium μ-(4,4′-bipyridine)bis[diaquatetranitratoneodymate(III)]-tris(4,4′-bipyridine) and a second monoclinic form of triaquatrinitratoholmium(III) – bis (4,4′-bipyridine)

The structures of (4-bipyH)₂[(μ-4-bipy)Nd₂(NO₃)₈(H₂O)₄]·3(4-bipy) (4-bipy = 4,4′-bipyridine; P2₁/c, a = 18.723(10), b = 10.720(6), c = 18.027(10) Å, β = 94.43(5)°, Z = 2; R = 0.066 for 4931 (diffractometer data) and of a second monoclinic form of [Ho(NO₃)₃(H₂O)₃]·2(4-bipy) (P2₁/c, a = 15.830(10), b = 21.44(3), c = 15.70(3) Å, β = 100.4(2)°, Z = 8; R = 0.091 for 2335 film data) are reported. In the first compound pairs of Nd atoms are bridged across a crystal inversion centre by a 4-bipy ligand, and 10-coordination is completed by one monodentate NO₃, three bidentate NO₃, and two H₂O ligands, with bond lengths Nd---N 2.70, Nd---OH₂(av.) 2.44, Nd---O(NO₃, av.) 2.56 Å. The second compound has a variant of the previously-reported monoclinic [Y(NO₃)₃(H₂O)₃]·2(4-bipy) structure, with doubling of the unit cell on a but with essentially no change in the geometry and orientation of the nine-coordinate complex. In both compounds the non-coordinated, non-protonated 4-bipy N atoms form hydrogen bonds with ligand H₂O.     

Anomalous carbonylation of [Pd(dppm)(O2CCF3)]2 to give an asymmetric μ-CO complex

The reactive palladium dimer, [Pd(dppm)(O₂CCF₃)]₂, is carbonylated to [Pd(dppm)(O₂CCF₃)]₂(μ-CO) in a reversible reaction with K = c. 7.2(2)x10⁴ atm⁻¹ (P_1/2 = c. 2.4 Torr). This is significantly larger than is expected based on the λ_max = 280 nm in the electronic spectrum. The product can be isolated in analytically pure form by crystallization under a CO atmosphere. It forms crystals in the monoclinic space group Cc with a = 18.584(5), b = 28.65(1), c = 11.164(3) Å and β = 95.16(2)°. The structure is significantly distorted. The bonding about the two palladium atoms is quite asymmetric. While one is close to a square planar geometry with a Pd---C(O) distance of 1.90(2) Å, the other is significantly pyramidalized and has a longer (2.00(2) Å) bond to the bridging CO. The Pd---Pd distance is only 2.896(2) Å, much shorter than that usually observed for formally non-bonded Pd atoms.     

Preparation, X-ray structure and solution behavior of [Ag(9-EtGH-N7)2]NO3·H2O (9-EtGH=9-ethylguanine)

The preparation and X-ray structure of [Ag(9-EtGH-N7)₂]NO₃·H₂O(9-EtGH=neutral 9-ethylguanine) is reported. The compound crystallizes in the triclinic system, space group P with a=7.063(6), b=7.153(3), c=11.306(10) Å, α=83.36(6), β=76.66(7), γ=81.44(6)°. The cation is centrosymmetric with Ag(I) coordinated via two N7 positions and Ag---N7 bond lengths of 2.11(1) Å. Applying ¹⁰⁹Ag NMR spectroscopy, complex formation constants for both the 1:1 complex (log β₁=0.6) and the title compound (log β₂=1.6) in Me₂SO have been determined.     

Preparation and characterization of some uranyl complexes of amino acids. The crystal structure of [UO2(γ-aminobutanoic acid)3] (NO3)2

Uranyl complexes of glycine, β-alanine and γ-aminobutanoic acid were prepared and characterized. All those studied or examined contain the aminoacids in the zwitterionic form binding the metal through the ionized carboxyl group. The structure of the title compound was determined by X-ray crystallography and refined to R=6.6%. The crystals are triclinic, space group P1, Z = 2, with a = 11.966(5), b = 12.054(5), c = 10.581(5) Å, α = 70.88(3)°, β = 109.89(3)°, and γ = 120.72(3)°. The uranyl group is equatorially bonded to the bidentate carboxylate of three molecules of the organic ligand forming a distorted hexagonal bipyramidal coordination geometry around the metal. U---O(equatorial) distances are in the range 2.24–2.48 Å.     

Crystallization and Preliminary X-Ray Analysis of Neuropsin, a Serine Protease Expressed in the Limbic System of Mouse Brain

Neuropsin (M_r25 032) is a serine protease expressed in the limbic system of mouse brain. It has been implicated in various neurological processes including formation of memory and may be important as a drug target in the treatment of epilepsy. The recombinant protein was produced using a baculovirus expression system and was purified. Two crystal forms were obtained by a hanging-drop vapor-diffusion method with polyethylene glycol. Preliminary X-ray crystallographic analysis revealed that crystal form I belongs to triclinic space groupP1 with unit cell dimensionsa= 97.16 Å,b= 97.12 Å,c= 46.75 Å and α = 99.17°, β = 99.77°, γ = 117.35°. Self-rotation function analysis of these data of form I indicates the position of a noncrystallographic threefold axis. There are six molecules in the crystallographic asymmetric unit. Crystal form II also belongs to triclinic space groupP1 but has unit cell dimensions ofa= 38.40 Å,b= 55.16 Å,c= 65.37 Å and α = 95.38°, β = 89.98°, γ = 110.46° with two molecules in the crystallographic asymmetric unit. Form II has a noncrystallographic twofold axis. Intensity data to 3.1 Å resolution for form I and to 2.2 Å resolution for form II have been collected.     

A spectroscopic model for the high pH form of sulfite oxidase

The syntheses and spectroscopic properties of two monomeric oxo-Mo(V) complexes [NMe₄][MoO(SC₆H₄---CH=N---C₆H₄O)(SAr)₂] (Ar=Ph (2a), PhCH₃ (2b)) exhibiting a novel S₃NO coordination site are described. The EPR parameters of the Mo(V) complexes are almost identical with the parameters for the high pH form of sulfite oxidase, allowing further predictions for the unknown coordination site of the molybdenum cofactor in such molybdenum-containing enzymes. The Mo(V) compounds react with water to form a μ-oxo-bridged Mo(V) dimer, which is readily oxidized by oxygen to give the monomeric dioxo-Mo(VI) complex MoO₂(SC₆H₄---CH=N---C₆H₄O)(sol) (4) (sol=acetonitrile; dimethyl sulfoxide (DMSO)). The structure of 4 has been determined by X-ray crystallography (space group P (No. 2), a=7.855(4), b=9.530(3), c=11.676(6) Å, α=103.96(3), β=99.03(3), γ=100.73(3)°, V=814.5 ų, ρ_calc=1.79 g cm⁻³, Z=2, R(F)=0.026, R(wF)=0.026). The geometry about the molybdenum is distorted octahedral, with two terminal oxo groups cis to each other.     

Binuclear complexes of a new hexadentate macrocyclic ligand. The crystal and molecular structure of [LCu2(CH3CO2)2](ClO4)2·5H2O

The 30-membered hexaaza macrocylic ligand, L (L=3,7,11,18,22,26-hexaazatricyclo-[26.2.2.2^13,16]tetratriaconta-1(31),13(33),14,16(34),28(32),29-hexaene), is capable of forming binuclear complexes with the divalent transition metal ions Ni, Cu and Zn. The two metal ions are bound by the two dipropylenetriamine units of the macrocycle. Extra coordination sites on the metal ions can be occupied by exogenous ligands such as acetate, chloride and thiocyanate. The crystal structure of one of the di-copper complexes is described: [LCu₂(CH₃CO₂)₂](ClO₄)₂·5H₂O crystallizes in the monoclinic space group P2₁/c (No. 14), with a=9.369(2), b=17.644(3), c= 27.466(3) Å, β=92.90(1)°, U=4534.7 ų and Z=4. The Cu1···Cu2 separation is 8.40(3) Å. The access for potential exogenous bridging ligands, to the cavity between the copper ions, is somewhat restricted by the two phenyl units of the macrocycle which appear almost parallel in the structure. The redox potential of the couple L(Cu²⁺)₂/L(Cu⁺)₂, recorded by cyclic voltammetry for the chloride adduct, [LCu₂Cl₂]Cl₂·5H₂O, is −0.061 V versus SCE in DMF.     

Synthesis, structural analysis and anticonvulsant activity of a ternary Cu(II) mononuclear complex containing 1,10-phenanthroline and the leading antiepileptic drug valproic acid

The synthesis and characterization of the binary complex of copper(II) with the antiepileptic drug valproic acid sodium salt (Valp) and the related ternary complex with 1,10-phenanthroline (phen) are reported, as well as the anticonvulsant properties of the latter. The characterization was carried out by means of elemental analyses, infrared (IR), UV–visible (UV–vis) spectrophotometry and Electron Paramagnetic Resonance (EPR). The X-ray crystal structure of the mononuclear complex bis(2-propylpentanoate)(1,10-phenanthroline)copper(II) [Cu(Valp)₂phen] is showed for the first time. It crystallized in C2/c space group with unit cell dimensions of a = 14.939(1) Å, b = 19.280(1) Å, c = 9.726(1) Å, β = 97.27(2)°, V = 2778.8(4) Å ³ and Z = 8. The carboxylates bond in an asymmetric chelating mode and the copper atom adopts a highly distorted octahedral coordination, characterized by the sum of the angles of 365.9° around Cu(II) and its nearest atoms in the CuN₂O₂ + O₂ chromophore instead of the expected 360° for a basal square planar geometry found in most Cu(II) complexes. Molecules assemble three by three through slipped π–π stacking of the aromatic phen with respectively 3.519 and 3.527 Å distances, in a head-to-tail arrangement. Studies of the anticonvulsant properties of this bioligand chelate evidenced its lack of efficacy in preventing MES-induced seizures. Interestingly, complex 4 protected mice against the Minimal Clonic seizures at doses that do not cause Rotorod toxicity, with an ED₅₀ documenting very potent anticonvulsant activity in this model of seizure, a particularly useful pharmacological profile of activity for the treatment of Petit Mal seizures.     

A study of the reactivity and structure of cyclic α,β-unsaturated Fischer-type carbene complexes

Cycloaddition reactions with α,β-unsaturated carbene complexes of the Fischer-type bearing the carbene carbon atom and the double bond incorporated in the same ring are described. Pentacarbonyl(2H-benzopyran-2- ylidene)chromium(0) complexes (2a-c) and pentacarbonyl(4-methoxy-3,3-dimethyl-2-oxacyclopentylidene)- chromium(0) (3) show a rather low reactivity towards 1,3-dipoles and 1,3-dienes. The reactions with diazomethane are regioselective but not chemoselective; compounds 2 and 3 show two sites of attack: the α,β carbon-carbon and the carbon-metal double bond. The crystal and molecular structures of 2a and 3 have been elucidated by single crystal X-ray analysis. Crystals of 2a are monoclinic, space group P2₁/c, a=7.614(3), b=14.033(3), c=12.766(3) Å, β=95.24°, V=1358.3(7) Å Z=4; crystals of 3 are triclinic, space group P , a=6.553(1), b=9.408(1), c=10.620(1) Å α=92.70(1), β=92.30(1), γ=92.12(1)°, V=653.0(1), ų, Z=2. Final agreement indices for 2a and 3 are R=0.034 and 0.033, respectively. Vibrational properties of the Cr(CO)₅ moiety were interpreted by FT-IR and FT-Raman spectroscopy. Electronic spectra and π electron distribution were interpreted by resonance Raman spectroscopy.