C≡N and N≡O Bond Cleavages of Acetonitrile and Nitrosyl Ligands at a Dimolybdenum Center to Render Ethylidyne and Acetamidinate Ligands.

Extended reduction of [Mo2Cp2(µ-Cl)(µ-PtBu2)(NO)2] (1) with Na(Hg) in acetonitrile (MeCN) at room temperature resulted in an unprecedented full cleavage of the C≡N bond of a coordinated MeCN molecule to yield the vinylidene derivative Na[Mo2Cp2(µ-PtBu2)(µ-CCH2)(NO)2], which upon protonation with (NH4)PF6 gave the ethylidyne complex [Mo2Cp2(µ-PtBu2)(µ-CMe)(NO)2] [Mo1-Mo2 = 2.9218(2) Å] in a selective and reversible way. Controlled reduction of 1 at 273 K yielded instead, after protonation, the 30-electron acetamidinate complex [Mo2Cp2(µ-PtBu2)(µ-κN:κN'-HNCMeNH)(µ-NO)]PF6 [Mo1-Mo2 = 2.603(2) Å], in a process thought to stem from the paramagnetic MeCN-bridged intermediate [Mo2Cp2(µ-PtBu2)(µ-NCMe)(NO)2], followed by a complex sequence of elementary steps including cleavage of the N≡O bond of a nitrosyl ligand.

Chemistry of a Nitrosyl Ligand κ:η-Bridging a Ditungsten Center: Rearrangement and N-O Bond Cleavage Reactions.

The novel nitrosyl-bridged complex [W2Cp2(µ-PtBu2)(µ-κ:η-NO)(CO)(NO)](BAr4) [Ar = 3,5-C6H3(CF3)2] was prepared in a multistep procedure starting from the hydride [W2Cp2(µ-H)(µ-PtBu2)(CO)4] and involving the new complexes [W2Cp2(µ-PtBu2)(CO)4](BF4), [W2Cp2(µ-PtBu2)(CO)2(NO)2](BAr4), and [W2(µ-κ:η5-C5H4)Cp(µ-PtBu2)(CO)(NO)2] as intermediates, which follow from reactions with HBF4·OEt2, NO, and Me3NO·2H2O, respectively. The nitrosyl-bridged cation easily added chloride upon reaction with [N(PPh3)2]Cl, with concomitant NO rearrangement into the terminal coordination mode, to give [W2ClCp2(µ-PtBu2)(CO)(NO)2], and underwent N-O and W-W bond cleavages upon the addition of CNtBu to give the mononuclear phosphinoimido complex [WCp(NPtBu2)(CNtBu)2](BAr4). Another N-O bond cleavage was induced upon photochemical decarbonylation at 243 K, which gave the oxo- and phosphinito-bridged nitrido complex [W2Cp2(N)(µ-O)(µ-OPtBu2)(NO)](BAr4), likely resulting from a N-O bond cleavage step following decarbonylation.

Electronic Structure and Donor Ability of an Unsaturated Triphosphorus-Bridged Dimolybdenum Complex.

The triphosphorus complex [Mo2Cp2(µ-η3:η3-P3)(µ-PtBu2)] was prepared in 83% yield by reacting the methyl complex [Mo2Cp2(µ-κ1:η2-CH3)(µ-PtBu2)(µ-CO)] with P4 at 333 K, a process also giving small amounts of the methyldiphosphenyl complex [Mo2Cp2(µ-η2:η2-P2Me)(µ-PtBu2)(CO)2]. The latter could be better prepared by first reacting the anionic complex Na[Mo2Cp2(µ-PtBu2)(µ-CO)2] with P4 to give the diphosphorus derivative Na[Mo2Cp2(µ-η2:η2-P2)(µ-PtBu2)(CO)2] and further reaction of the latter with MeI. Density functional theory calculations on the title complex revealed that its triphosphorus group can be viewed as an allylic-like P3- ligand acting as a six-electron donor via the external P atoms, while coordination of the internal P atom involves donation from the π orbital of the ligand and back-donation to its π* orbital, both interactions having a weakening effect on the Mo-Mo and P-P connections. The reactivity of the title compound is dominated by the electron-donor ability associated with the lone pairs located at the P atoms. Its reaction with CF3SO3Me gave [Mo2Cp2(µ-η3:η3-P3Me)(µ-PtBu2)](CF3SO3) as a result of methylation at an external atom of the P3 ligand, while its reaction with [Fe2(CO)9] enabled the addition of one, two, or three Fe(CO)4 fragments at these P atoms, but only the diiron derivative [Mo2Fe2Cp2(µ-η3:η3:κ1:κ1-P3)(µ-PtBu2)(CO)8] could be isolated. This complex bears a Fe(CO)4 fragment at each of the external atoms of the P3 ligand, and the central P atom of the latter displays the lowest 31P chemical shift reported to date (δP -721.8 ppm). The related complexes [Mo2M2Cp2(µ-η3:η3:κ1:κ1-P3)(µ-PtBu2)(CO)10] (M = Mo, W) were prepared by reacting the title compound with the corresponding [M(CO)5(THF)] complexes in toluene, while reaction with [Mo(CO)4(THF)2] also enabled the formation of the heptanuclear derivative [Mo7Cp4(µ-η3:η3:κ1:κ1-P3)2(µ-PtBu2)2(CO)14]. The interatomic distances in the above compounds indicate that the central Mo2P3 skeleton of these molecules is little modified by the attachment of 16-electron M(CO)n fragments at the external atoms of the P3 ligand.

Effects of a Physical Activity Program Potentiated with ICTs on the Formation and Dissolution of Friendship Networks of Children in a Middle-Income Country.

This paper assesses the potential cohesion effect of a physical activity (PA) school-based intervention potentiated using text messages (SMS) through analyzing longitudinally the friendship network structure and the mechanisms of the formation and dissolution of friendships. Three schools (n = 125 participants) in Bogotá, Colombia, were randomly assigned into three groups: Modulo Activo Recreo Activo (MARA) + SMS (networks 1 and 2), MARA (networks 3 and 4), and control (no intervention: networks 5-7). We collected socio-economic, health-related, network structure, and intervention satisfaction variables in the baseline and after 10 weeks on July-November 2013. For each classroom network, we conducted four models using a temporal and static network approach to assess (1) temporal social network changes, (2) friendship homophily, (3) friendship formation and dissolution mechanisms, and (4) effect of SMS on the networks' cohesion. We found that (1) social cohesion emerged in the four intervened networks that were measured over time with transitivity and homophily driven by clustering, (2) the intervention affected the mechanisms of friendship formation and dissolution, and (3) MARA + SMS on average created more social cohesion and 3.8 more friendships than the program alone. Potentially, school-based interventions with information and communication technologies (ICT) such as MARA + SMS could encourage social cohesion among children. The particular characteristics of each school network need to be considered when developing school-based interventions.

Estudios sobre una prueba biologica en la esquizofrenia / Studies about a biological test in schizophenia

La presencia de antigeno del virus Herpes Simplex Hominis Tipo I en neuronas del sistema limbico de pacientes esquizofrenicos fallecidos, en fetos de madres esquizofrenicas y en embriones de pollo experimentalmente inoculados con liquido cefalico-raquideo, nos hizo considerar la posibilidad del desarrollo de una prueba biologica diagnostica y pronostica de la enfermedad a partir de marcadores perifericos: sangre y liquido cefalo-raquideo. En este ultimo caso la proximidad anatomica y fisiologica con el Sistema Nervioso Central aumenta su valor en la interpretacion de los resultados. La prueba consiste en la obtencion de una pequena muestra de liquido cefaloraquideo la que se incuba con antisueros especificos y sueros secundarios marcados con oro coloidal. La positividad encontrada hasta el momento predice su utilizacion con fines diagnosticos y pronosticos en pacientes y en poblaciones de alto riesgo, en la investigacion de la enfermedad, asi como en el perfeccionamiento de la misma a partir de metodos microanaliticos. El examen del liquido amniotico de embriones de pollo experimentalmente inoculados constituyen un elemento complementario ni solo para el diagnostico positivo, sino para futuros ensayos en el tratamiento preventivo de la enfermedad