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

Diastereoselective insertion of isocyanide into the alkyl metal bond of methylbenz[e]indenyl ansa-zirconocene complexes

Alkylation of ansa-zirconocene [Zr{(η5-C5H5)SiMe2(MBI)}Cl2] (MBI = η5-2-Me−C13H7) with MgRCl gave the dimethyl complex [Zr{(η5-C5H5)SiMe2(MBI)}Me2], but unresolvable mixtures containing mono-alkylated compounds were obtained when bulkier alkyls were used. However pure dialkyl complexes [Zr{(η5-C5H5)SiMe2(MBI)}R2] (R = CH2Ph, CH2SiMe3) were easily obtained using K(CH2Ph) and Li(CH2SiMe3) as alkylating agents. Diastereoselective insertion into the MBI-unprotected Zr−R bond was observed when all of these dialkyl complexes were treated with 2,6-xylyl isocyanide to give the iminoacyl compounds [Zr{(η5-C5H5)SiMe2(MBI)}R{CR[η2-N-(2,6-xylyl)]}] (R = Me, CH2Ph, CH2SiMe3). All of the new complexes were characterized by NMR spectroscopy and the X-ray molecular structures of the dibenzyl and the imino-benzyl compounds were determined. The catalytic activity for ethene polymerization and ethene/1-hexene copolymerization of the dichloro zirconocenes [Zr{(η5-C5H5)EMe2(MBI)}Cl2] (E = C, Si), activated with methylalumoxane (MAO), was measured.Repsol-YP

Synthetic and reactivity studies of mono- and dicyclopentadienyl titanium, zirconium and hafnium complexes with the chlorodimethylsilyl-cyclopentadienyl ligand. X-ray molecular structure of Hf{(η5-C5H4)SiMe2OSiMe2(η5-C5H4)}Cl2 and Zr(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2-η-NtBu)Cl

Reaction of the disilylated cyclopentadiene C5H4(SiClMe2)(SiMe3) with HfCl4, in heptane, gave the monocyclopentadienyl complex Hf(η5-C5H4SiClMe2)Cl3 (1c). Addition of two equivalents of C5H5(SiClMe2) to a solution of MCl4, in toluene under reflux and in the presence of two equivalents of NEt3, afforded the dichloro derivatives M(η5-C5H4SiClMe2)2Cl2 [M=Ti (2a), Hf (2c)]. Compounds 2a and 2c react with a stoichiometric amount of water with selective hydrolysis of the SiCl bonds to give the tetramethyldisiloxane-bridged diciclopentadienyl complexes M{(η5-C5H4)SiMe2OSiMe2(η5-C5H4)}Cl2 [M=Ti (3a), Hf (3c)]. The reaction of the trichloro metal compounds M(η5-C5H4SiClMe2)Cl3 with Tl(1,3-tBu2C5H3), K(C5Me5) or Tl(C5H5) afforded the dichloro mixed dicyclopentadienyl MCp′(η5-C5H4SiClMe2)Cl2 derivatives [Cp′=1,3-tBu2C5H3, M=Ti (4a), Zr (4b), Hf (4c); Cp′=C5Me5, M=Zr (5b), Hf (5c); Cp′=C5H5, M=Hf (6c)]. The SiCl bond of the mixed dicyclopentadienyl complexes M(η5-1,3-tBu2C5H3)(η5-C5H4SiClMe2)Cl2, [M=Ti (4a), Zr (4b), Hf (4c)] reacts selectively with one equivalent of LiNHtBu in toluene at 50–60°C to give the amidosilyl(cyclopentadienyl) compounds M(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2NHtBu)Cl2, [M=Ti (7a), Zr (7b), Hf (7c)]. The same reaction with two equivalents of the lithium amide gives the ansa-cyclopentadienylsilyl-amido compounds M(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2-η-NtBu)Cl [M=Ti (8a), Zr (8b), Hf (8c)]. The X-ray molecular structure of Hf{(η5-C5H4)SiMe2OSiMe2(η5-C5H4)}Cl2 (3c) and Zr(η5-1,3-tBu2C5H3)(η5-C5H4SiMe2-η-NtBu)Cl (8b) have been determined by diffraction methods.Financial support for this research by DGICYT (Project PB97-0776) is gratefully acknowledged

Ecuaciones diferenciales para el proceso de flujo de aguas subterráneas a través del suelo y análisis de la importancia de los estudios de los niveles freáticos para las obras civiles en Valledupar

El subsuelo tiende a comportarse de múltiples maneras con respecto al agua mucha las cuales en contacto con este se clasifican en subterráneas y superficiales, una parte de la información del comportamiento de las aguas subterráneas es su comportamiento con respecto al medio dónde se encuentran y el entorno que la rodea