Insertion of carbon dioxide and isocyanide into tantalum-amide and tantalum-methyl bonds

The methyl–amide complex [TaCp*(NtBu)Me(NMe2)] (1a) was isolated by reaction of the chloro–methyl [TaCp*(NtBu)MeCl] complex with LiNMe2. Reaction of the mono-amide compounds [TaCp*(NtBu)XY] (X=NMe2, Y=Me (1a); X=NHtBu, Y=Me (1b), Cl (1c)) with CO2 gives the η2-carbamate derivatives [TaCp*(NtBu)(η2-O2CX)Y] (X=NMe2, Y=Me (2a); X=NHtBu, Y=Me (2b), Cl (2c)). A similar reaction with the di-amide complex [TaCp*(NtBu)(NHtBu)2] (1d) gives the di-carbamate derivative [TaCp*(NtBu){η2-O2C(NHtBu)}{η1-O2C(NHtBu)] (2d). Reaction of the methyl–carbamate (2a) with isocyanide CNAr (Ar=2,6-Me2C6H3) gives the η2-iminoacyl–η1-carbamate complex [TaCp*(NtBu){η2-C(Me)NAr}{η1-O2C(NMe2)] (3a). Formation of the related compound [TaCp*(NtBu){η2-C(Me)NAr}{η1-O2C(NHtBu)}] (3b) was only detected by NMR spectroscopy in C6D6 or CDCl3 whereas the reaction of 2b in hexane gives the η1-iminoacyl–η2-carbamate complex [TaCp*(NtBu){η1-C(Me)NAr}{η2-O2C(NHtBu)}] (3b′). All of the new compounds were characterized by elemental analysis and 1H- and 13C-NMR spectroscopy

Oxo and imido/imido exchange and C-H activation reactions based on pentamethylcylopentadienyl imido tantalum complexes

Reactions of [TaCp*Cl4] with two, three and four equivalents of LiNHt Bu give the halo- and amido-imido complexes [TaCp*Cl2(Nt Bu)] (1a), [TaCp*Cl(Nt Bu)(NHt Bu)] (2) and [TaCp*(Nt Bu)(NHt Bu)2] (3), respectively. The related complex [TaCp*Cl2{N(2,6-Me2C6H3)}] (1b) is prepared by a similar reaction using two equivalents of Li[NH(2,6-Me2C6H3)]. Complex 3 can be transformed into 2 and further into 1a by reaction with SiClMe3. Complex 1a reacts with CNt Bu to give the 18-electron adduct [TaCp*Cl2(Nt Bu)(CNt Bu)] (4) whereas addition of excess CN(2,6-Me2C6H3) results in reductive elimination of the carbodiimide t BuN C N(2,6-Me2C6H3) (5) to give [TaCp*Cl2{CN(2,6-Me2C6H3)}3]. However complex 1b does not react with any of the isocyanide ligands. Both complexes 1a and 1b react with PhCHO undergoing imido/oxo exchange to give the imines PhCH NR (R=t Bu, 2,6-Me2C6H3 (6)) and dimeric [TaCp*Cl2(O)]2 or trimeric [(TaCp*Cl)3(m2-Cl)(m2-O)3(m3-O)] oxo-complexes, whereas only 1a reacts with CO2, PhCH NR% (R%=Ph, Me) and (2,6-Me2C6H3)N C Nt Bu producing t BuN CO, PhCH Nt Bu and t BuN C Nt Bu, respectively and the corresponding oxo or imido tantalum derivative. None of the complexes reacts with CO or NCR (R=Me, Ph). The complex [TaCp*Me(Nt Bu)(NHt Bu)] activates C–H bonds when heated in benzene and toluene affording [TaCp*Ph(Nt Bu)(NHt Bu)] (7) and a mixture of [TaCp*(m-MeC6H4)(Nt Bu)(NHt Bu)] 8a and [TaCp*(pMeC6H4)(Nt Bu)(NHt Bu)] (8b). All of the reported organic compounds and tantalum complexes were characterized by 1 H- and 13C-NMR spectroscopyThe authors acknowledge DGICYT (project PB97-0776) for financial support and J.S.N. acknowledges MEC for a fellowship

Effect of NPA on adventitious root induction and root development in leaves of chestnut microshoots

Peer reviewe

Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

The niobium complex [NbCpClCl4] (CpCldouble bond; length as m-dashη5-C5H4(SiCl2Me)) (1) with a functionalized (dichloromethylsilyl)cyclopentadienyl ligand was isolated by the reaction of [NbCl5] with C5H4(SiCl2Me)(SiMe3). Complex 1 was a precursor for the imido silylamido derivative [NbCpNCl2(NtBu)] (CpNdouble bond; length as m-dashη5-C5H4[SiClMe(NHtBu)]) (2) after addition of LiNHtBu, which subsequently gave the dichlorosilyl compound [NbCpClCl2(NtBu)] (3) when reacted with SiCl3Me. Addition of LiNHtBu to complex 2 gave the niobium amido complex [NbCpNCl(NHtBu)(NtBu)] (4), which slowly evolved with exchange of the niobium-amido and the silicon-chloro groups to give the dichloroniobium complex [NbCpNNCl2(NtBu)] (CpNNdouble bond; length as m-dashη5-C5H4[SiMe(NHtBu)2]) (5). Reaction of 2 with excess LiNHtBu gave the silyl-η-amido constrained geometry complexes [Nb{η5-C5H4[SiMe(NHtBu)(-η-NtBu)]}(NHtBu)(NtBu)] (6) and [Nb{η5-C5H4[SiClMe(-η-NtBu)]}(NHtBu)(NtBu)] (7), whereas addition of one equimolecular amount of LiNHtBu to 5 in C6D6 afforded complex [NbCpNNCl(NHtBu)(NtBu)] (8). All of the new complexes were characterized by 1H, 13C and 29Si NMR spectroscopy.Universidad de Alcal

Prevalencia y riesgo anual de infeccion por tuberculosis en la población escolar de 7 años de edad de Ceuta

ResumenObjetivoConocer la prevalencia de la infección tuberculosa y el riesgo anual de infección en la población escolar de Ceuta.MétodoEstudio transversal. Se realizó la prueba de la tuberculina (2UT RT-23 Tween 80) a los niños de 7 años de edad escolarizados en Ceuta en 2008. Se consideraron positivos los niños no vacunados con una induración ≥5mm a las 72 horas.ResultadosSe estudiaron 612 niños. La prevalencia de la infección fue del 0,98% (intervalo de confianza del 95%, margen de error del 2,5%). Su distribución mostró diferencias entre las tres zonas de salud, y fue mayor en las zonas más deprimidas, donde llegó al 2,07%. El riesgo anual de infección fue del 0,15%.ConclusionesLa prevalencia de la infección es de las más altas de España, según los últimos estudios realizados. Los resultados no se corresponden con los datos epidemiológicos de tuberculosis de Ceuta, al tener en cuenta los casos importados.AbstractObjectiveTo determine the prevalence of tuberculosis infection and annual risk of infection in the school population of Ceuta.MethodA cross-sectional study was conducted. A tuberculin test (2UT RT-23 Tween 80) was given to 7-year-old schoolchildren in Ceuta in 2008. A positive result was considered as an induration of ≥5mm at 72hours in unvaccinated children.ResultsA total of 612 children were studied. The prevalence of tuberculosis infection was 0.98% (95% confidence interval with a 2.5% margin of error). The distribution showed differences among three health areas, and was greatest in the most deprived area (2.07%). The annual risk of infection was 0.15%.ConclusionsAccording to the most recent studies, the prevalence of tuberculosis infection in Ceuta is one of the highest of Spain. Our results do not agree with the epidemiological data for tuberculosis in Ceuta, which also includes imported cases

Thinking small: zinc-sensing by the gut epithelium.

pre-print341 K

Caracterización y análisis de expresión del gen TCTP en fagáceas

Peer reviewe

Validity of the Computerized Battery for Neuropsychological Evaluation of Children (BENCI) in Spanish Children: Preliminary Results

Study of the neurodevelopment of children is vital to promote good quality of life during childhood. Few batteries showing adequate reliability and validity indices are available to evaluate the different neuropsychological domains. The objective of this study was to obtain initial evidence on the validity of the Computerized Battery for Neuropsychological Evaluation of Children (BENCI) in a Spanish population. To assess the validity of the BENCI battery and other measures of task switching, abstract reasoning, linguistic abilities, processing speed, and attention were used. The sample was composed of a total of 73 children aged 9, 10, and 11 years. Significant differences among age groups were observed in the domains of sustained attention, memory, and executive function. In addition, the BENCI subtests showed statistically significant correlations with the other neuropsychological tools. Further research is warranted on the relationship of the BENCI with other tests in wider age groups and to assess the factorial structure of the scale and the reliability values of the subtests. In conclusion, this study seems to indicate that the Spanish version of the BENCI has promising validity to be used for evaluating the main neuropsychological domains in children.Conselleria d'Educacio, Investigacio, Cultura i Esport de la Generalitat Valenciana (Proyectos I+D+i desarrollados por grupos de investigacion emergentes) GV/2017/166Agencia Andaluza de Cooperacion Internacional al Desarrollo de la Junta de Andalucia (Proyectos de Investigacion para la Cooperacion Internacional al Desarrollo AACID-Universidades) 2020U100

Dinuclear dialkoxo-bridged cyclopentadienylsiloxo titanium complexes

The dinuclear dialkoxo-bridged complexes [(TiCl)2(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (O2L = 1,2-O2C2H41a, 1,2-O2C6H41b, 1,2-(OCH2)2C6H41c, O2SiPh21d) were obtained by reaction of [(TiCl2)2(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (A) with the corresponding dilithium salt (1a) or diol (1b, 1c, 1d). Alkylation of 1a and 1b with ClRMg afforded [(TiR)2(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (O2L = 1,2-O2C2H4, R = Me 2a, Bz 3a; O2L = 1,2-O2C6H4, R = Me 2b, Bz 3b). Addition of four equiv. of LiOiPr to A afforded [{Ti(OiPr)2}2(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (4). Reaction of 1a with Al(C6F5)3 produced the elimination of the dialkoxo ligand to give [{TiCl(C6F5)}2(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (5), whereas the same reaction of 1b with Al(C6F5)3 produced the oxo-alane adduct [(TiCl)2(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O·Al{C6F5}3)})] (O2L = 1,2-O2C6H46) which was further transformed to give a mixture of 5 and [(TiCl){Ti(C6F5)}(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (O2L = 1,2-O2C6H47). One benzyl group of complexes 3 was abstracted with E(C6F5)3 (E = B, Al) to give the monoionic compounds [Ti(TiBz)(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})][BzE(C6F5)3] (O2L = 1,2-O2C2H4, E = B 8B, Al 8Al; O2L = 1,2-O2C6H4, E = B 9B), although 8Al was unstable in CD2Cl2 evolving to a mixture of compounds where [(TiBz)2(μ-Cl)(μ-{(η5-C5Me4SiMeO)2(μ-O)})][BzAl(C6F5)3] (10) was identified, and compound 9B was also unstable at ambient temperature. Polymerization of ε-caprolactone was only achieved with the tetraalkoxo compound 4. All of these complexes were characterized by NMR spectroscopy and 1a, 1b and 7 by X-ray diffraction studies

Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl](Ar=2,6-Me2C6H3)

Reactions of the magnesium imides [Mg(NAr)(THF)]6 (Ar = 2,6-Me2C6H3, 1a; Ph, 1b) with [NbCpClCl4] (CpCl = η5-C5H4(SiMe2Cl)) afforded the imido complexes [NbCpClCl2(NAr)] (Ar = 2,6-Me2C6H3, 2a; Ph, 2b) in good yield. Compound 2a reacted with excess LiNH(2,6-Me2C6H3) to give the silyl-η-amido complex [Nb(η5-C5H4SiMe2-η1-NAr)Cl(NAr)] (Ar = 2,6-Me2C6H3, 3a). Hydrolysis of the Si–Cl bond of compounds 2a and 2b yielded the dinuclear complexes [{NbCl2(NAr)}2{(η5-C5H4SiMe2)2(μ-O)}] (Ar = 2,6-Me2C6H3, 4a; Ph, 4b), respectively. All of the new compounds reported were characterized by NMR spectroscopy and the molecular structure of 3a was determined by X-ray diffraction methods.We gratefully acknowledge the Ministerio de Educación y Ciencia (Project MAT2004-02614) and\ud DGUI-Comunidad de Madrid (Project GR/MAT/0622/2004) (Spain) for financial support. R.A.-M. acknowledges MCyT for a fellowshi