Synthesis and characterization of methyl-phenyl-substituted cyclopentadienyl zirconium complexes

The trisubstituted methyl-phenyl-silyl-cyclopentadienes [Me-Ph-C5H3(SiMe2X)] (X = Me, Cl, NHt-Bu) and [(Me-Ph-C5H3)2SiMe2] and the lithium salts Li2[Me-Ph-C5H2(SiMe2Nt-Bu)] and Li2[(Me-Ph-C5H2)2SiMe2] have been isolated by conventional methods and characterized by NMR spectroscopy. Desilylation of [Me-Ph-C5H3(SiMe3)] with ZrCl4(SMe2)2 gave the monocyclopentadienyl complex [Zr(η5-1-Ph-3-Me-C5H3)Cl3]. The ansa-metallocene [Zr{(η5-2-Me-4-Ph-C5H2)SiMe2(η5-2-Ph-4-Me-C5H2)}Cl2] was obtained from the mixture of isomers formed by transmetallation of Li2[(Me-Ph-C5H2)2SiMe2] to ZrCl4 and characterized as the meso-diastereomer by X-ray diffraction methods. Similar transmetallation of Li2[Me-Ph-C5H2(SiMe2Nt-Bu)] gave the silyl-η-amido complex [Zr{η5-2-Me-4-Ph-C5H2(SiMe2-η-Nt-Bu)}Cl2] that was further alkylated to give [Zr{η5-2-Me-4-Ph-C5H2(SiMe2-η-Nt-Bu)}R2] (R = Me, CH2Ph) and used as a catalyst precursor, activated with MAO, for ethene and propene polymerization. All of the new compounds were characterized by elemental analysis and NMR spectroscopy.Ministerio de Educación, Cultura y Deport

Hydro- and chloro-substituted silyl- and silyl-η1 -amido-η5- tetramethylcyclopentadienyl titanium complexes

Chlorosilyl-cyclopentadienyl titanium precursors [Ti(η5-C5Me4SiMeXCl)Cl3] (X=H 2, Cl 3) were prepared by reaction of TiCl4 with the trimethylsilyl derivatives of the corresponding cyclopentadienes. Methylation of these compounds with MgClMe under appropriate conditions afforded the methyl complexes [Ti(η5-C5Me4SiMe2R)XMe2] (R=H, X=Cl 5, Me 6; R=X=Me 7). Reactions of 2 and 3 with two equivalents of LiNHtBu afforded the ansa-silyl-η-amido compounds [Ti{η5-C5Me4SiMeX(η1-NtBu)}Cl2] (X=H 8, Cl 9). Methylation of 8 gave [Ti{η5-C5Me4SiMeH(η1-NtBu)}Me2] 10. Complex 9 was also obtained by reaction of 8 with BCl3, whereas the same reaction using alternative chlorinating agents (TiCl4, HCl) resulted in deamidation to give 2, which was also converted into 3 by reaction with BCl3. All of the new compounds were characterized by NMR spectroscopy and the molecular structures of 2 and 4 were determined by X-ray diffraction methods.Comunidad Autónoma de Madri

Methylbenz[e]indenyl asymmetric ansa-metallocene and silylamido zirconium complexes

2-(2-Methylbenz[e]indenyl)-2-cyclopentadienyl-propane [MeC13H8CMe2C5H5] (1) (MBICMe2Cp), was synthesized by reaction of LiMBI with 6,6-dimethylfulvene. The silyl derivatives [MeC13H8SiMeRCl] (R=Me 2, H 4) were isolated by reaction of 2-methylbenz[e]indene (LiMBI) with SiMeRCl2 and further reactions of 2 and 4 with NaCp afforded the silyl-bridged compounds [MeC13H8SiMeRC5H5] (R=Me 3, H 5). Metallation of 1 and 3 with 2 equiv. of LiBu gave the dilithium salts Li2[MeC13H7EMe2C5H4)] (E=C 6, Si 7) which were reacted with ZrCl4(THF)2 to obtain the ansa-metallocenes [Zr(MeC13H7EMe2C5H4)Cl2] (E=C 8, Si 9). A similar reaction of 5 with 2 equiv. of LiBu provided a mixture of the two diastereomers [Zr{MeC13H7SiMeBuC5H4}Cl2] (10a, 10b). Analogous metallation of [MeC13H8SiMe2(NH-t-Bu)] gave Li2[MeC13H7SiMe2(N-t-Bu)] which was used to prepare the amidosilyl derivatives [M{MeC13H7SiMe2η-(N-t-Bu)}Cl2] (M=Zr 11, Ti 12) by reaction with ZrCl4(THF)2 and TiCl3(THF)3 and further oxidation with PbCl2 (Ti). All of the new complexes were characterized by elemental analysis and NMR spectroscopy, and the molecular structures of complexes 9 and 10a were studied by X-ray diffraction methods.Financial support of our work by MCyT (Project MAT2001-1309) is gratefully acknowledged. A.S. is grateful to Repsol-YPF for a fellowship

Synthesis and Neurotrophic Activity Studies of Illicium Sesquiterpene Natural Product Analogues

Neurotrophic natural products hold potential as privileged structures for the development of therapeutic agents against neurodegeneration. However, only a few studies have been conducted to investigate a common pharmacophoric motif and structure–activity relationships (SARs). Here, an investigation of structurally more simple analogues of neurotrophic sesquiterpenes of the illicium family is presented. A concise synthetic route enables preparation of the carbon framework of (±)-Merrilactone A and (±)-Anislactone A/B on a gram scale. This has allowed access to a series of structural analogues by modification of the core structure, including variation of oxidation levels and alteration of functional groups. In total, 15 derivatives of the natural products have been synthesized and tested for their neurite outgrowth activities. Our studies indicate that the promising biological activity can be retained by structurally simpler natural product analogues, which are accessible by a straightforward synthetic route

Neutral and Cationic [Bis(η1-amidosilyl)-η5-cyclopentadienyl]titanium and -zirconium complexes: synthesis, X-ray molecular structures and DFT calculations

Treatment of LiNHtBu with THF solutions of C5H4(SiMe2Cl)2 gave C5H4(SiMe2NHtBu)2 (1). Deprotonation of 1 with M(NMe2)4 (M = Ti, Zr) under different conditions provided the monocyclopentadienyl complexes [M{η5-C5H3- [SiMe2(NHtBu)]2}(NMe2)3] [M = Ti (2), Zr (3)] and the single (η-amidosilyl)cyclopentadienyl compounds [M{η5-C5H3[SiMe2(NHtBu)][SiMe2(η1-NtBu)]}(NMe2)2] [M = Ti (4), Zr (5)]. The related dibenzyl compounds [M{η5-C5H3[SiMe2- (NHtBu)][SiMe2(η1-NtBu)]}(CH2Ph)2] [M = Ti (6), Zr (7)] resulted from treatment of 1 with M(CH2C6H5)4 (M = Ti, Zr). Further deprotonation of the amido complexes 4 and 5 and the benzyl complexes 6 and 7 by heating in toluene solution gave the bis(η-amidosilyl)cyclopentadienyl complexes [M{η5-C5H3[SiMe2(η1-NtBu)]2}(NMe2)] [M = Ti (8), Zr (9)] and [M{η5-C5H3[SiMe2(η1-NtBu)]2}(CH2Ph)] [M = Ti (10), Zr (11)], respectively. Treatment of the monobenzyl complexes 10 and 11 with B(C6F5)3 yielded the cationic compounds [M{η5-C5H3[SiMe2(η1-NtBu)]2}]+ as [(CH2Ph)B(C6F5)3] − [M = Ti (12), Zr (13)] salts. All new compounds were characterized by NMR spectroscopy, and the crystal structures of 10 and 13 were studied by diffraction methods. DFT calculations for the neutral and cationic species are described and provide an explanation for the unusual η1 coordination of a phenyl ring to a group-4 metal cationThe authors acknowledge the MCyT (project MAT2001-1309) for\ud financial support and the EC (project COST-D12/0016/98). J. C.\ud acknowledges CAM for a fellowship

2,4-Bis(diphenyl­phosphan­yl)-1,1,2,3,3,4-hexa­phenyl-1,3-diphospha-2,4-dibora­cyclo­butane tetra­hydro­furan sesqui­solvate

In the title compound, C60H50B2P4·1.5C4H8O, the diphospha­diborane mol­ecule lies on an inversion centre, whereas the disordered tetra­hydro­furan solvent mol­ecule is in a general position with a partial occupancy of 0.75. The diphosphadiborane mol­ecule consists of an ideal planar four-membered B2P2 ring with an additional phenyl and a –PPh2 group attached to each B atom

Orbital Configurations and Magnetic Properties of Double-Layered Antiferromagnet Cs3_3Cu2_2Cl4_4Br3_3

We report the single-crystal X-ray analysis and magnetic properties of a new double-layered perovskite antiferromagnet, Cs$_3$Cu$_2$Cl$_4$Br$_3$. This structure is composed of Cu$_2$Cl$_4$Br$_3$ double layers with elongated CuCl$_4$Br$_2$ octahedra and is closely related to the Sr$_3$Ti$_2$O$_7$ structure. An as-grown crystal has a singlet ground state with a large excitation gap of $\Delta/k_{\rm B}\simeq 2000$ K, due to the strong antiferromagnetic interaction between the two layers. Cs$_3$Cu$_2$Cl$_4$Br$_3$ undergoes a structural phase transition at $T_{\rm s}\simeq330$ K accompanied by changes in the orbital configurations of Cu$^{2+}$ ions. Once a Cs$_3$Cu$_2$Cl$_4$Br$_3$ crystal is heated above $T_{\rm s}$, its magnetic susceptibility obeys the Curie-Weiss law with decreasing temperature even below $T_{\rm s}$ and does not exhibit anomalies at $T_{\rm s}$. This implies that in the heated crystal, the orbital state of the high-temperature phase remains unchanged below $T_{\rm s}$, and thus, this orbital state is the metastable state. The structural phase transition at $T_{\rm s}$ is characterized as an order-disorder transition of Cu$^{2+}$ orbitals.Comment: 6pages. 6figures, to appear in J. Phys. Soc. Jpn. Vol.76 No.

Synthèse et caractérisation de nouveaux complexes aryloxy à base de tungstène

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Revealing the molecular signatures of host-pathogen interactions.

Advances in sequencing technology and genome-wide association studies are now revealing the complex interactions between hosts and pathogen through genomic variation signatures, which arise from evolutionary co-existence

Alkali Metal Bismuth(III) Chloride Double Salts

Evaporative co-crystallization of MCl (M = Na, K, Rb, Cs) with BiOCl in aqueous HCl produces double salts: MxBiyCl(x+3y)·zH2O. The sodium salt, Na2BiCl5·5H2O (monoclinic P21/c, a = 8.6983(7) Å, b = 21.7779(17) Å, c = 7.1831(6) Å, β = 103.0540(10)°, V = 1325.54(19) Å3, Z = 4) is composed of zigzag chains of μ2-Cl-cis-linked (BiCl5)n2n– chains. Edge-sharing chains of NaCln(OH2)6−n octahedra (n = 0, 2, 3) are linked through μ3-Cl to Bi. The potassium salt, K7Bi3Cl16 (trigonal R−3c, a = 12.7053(9) Å, b = 12.7053(9) Å, c = 99.794(7) Å, V = 13,951(2) Å3, Z = 18) contains (Bi2Cl10)4– edge-sharing dimers of octahedra and simple (BiCl6)3– octahedra. The K+ ions are 5- to 8-coordinate and the chlorides are 3-, 4-, or 5-coordinate. The rubidium salt, Rb3BiCl6·0.5H2O (orthorhombic Pnma, a = 12.6778(10) Å, b = 25.326(2) Å, c = 8.1498(7) Å, V = 2616.8(4) Å3, Z = 8) contains (BiCl6)3– octahedra. The Rb+ ions are 6-, 8-, and 9-coordinate, and the chlorides are 4- or 5-coordinate. Two cesium salts were formed: Cs3BiCl6 (orthorhombic Pbcm, a = 8.2463(9) Å, b = 12.9980(15) Å, c = 26.481(3) Å, V = 2838.4(6) Å3, Z = 8) being comprised of (BiCl6)3– octahedra, 8-coordinate Cs+, and 3-, 4-, and 5-coordinate Cl−. In Cs3Bi2Cl9 (orthorhombic Pnma, a = 18.4615(15) Å, b = 7.5752(6) Å, c = 13.0807(11) Å, V = 1818.87(11) Å3, Z = 4) Bi octahedra are linked by μ2-bridged Cl into edge-sharing Bi4 squares which form zigzag (Bi2Cl9)n3n– ladders. The 12-coordinate Cs+ ions bridge the ladders, and the Cl− ions are 5- and 6-coordinate. Four of the double salts are weakly photoluminescent at 78 K, each showing a series of three excitation peaks near 295, 340, and 380 nm and a broad emission near 440 nm