Di-μ2-bromido-bis­[bromido(η6-1,2,4,5-tetra­methyl­benzene)ruthenium(II)]

The asymmetric unit of the title compound, [Ru2Br4(C10H14)2], contains one half of the centrosymmetric mol­ecule. Each Ru center is coordinated by tetra­methyl­benzene ring in a η6-coordination mode, and one terminal and two bridging bromine atoms. The aromatic rings and the Ru2Br2 four-membered ring form a dihedral angle of 55.99 (8)°. In the crystal structure, weak inter­molecular C—H⋯Br inter­actions link mol­ecules into chains propagated in [001]

Access to Enantiomerically Pure P ‐Stereogenic Primary Aminophosphine Sulfides under Reductive Conditions

Stereochemically pure phosphines with phosphorus-heteroatom bonds and P-centered chirality are a promising class of functional building blocks for the design of chiral ligands and organocatalysts. A route to enantiomerically pure primary aminophosphine sulfides was opened through stereospecific reductive C−N bond cleavage of phosphorus(V) precursors by lithium in liquid ammonia. The chemoselectivity of the reaction as a function of reaction time, substrate pattern, and chiral auxiliary was investigated. In the presence of exclusively aliphatic groups bound to the phosphorus atom, all competing reductive side reactions are totally prevented. The absolute configurations of all P-stereogenic compounds were determined by single-crystal X-ray diffraction analysis. Their use as synthetic building blocks was demonstrated. The lithium salt of (R)-BINOL-dithiophosphoric acid proved to be a useful stereochemical probe to determine the enantiomeric purity. Insights into the coordination mode of the lithium-based chiral complex formed in solution was provided by NMR spectroscopy and DFT calculations

Di-μ2-chlorido-bis­[chlorido(η6-hexa­methyl­benzene)ruthenium(II)]

Dimeric mol­ecules of the title compound, [Ru2Cl4(C12H18)2], are located on a crystallographic centre of inversion with one mol­ecule in the asymmetric unit. The hexa­methyl­benzene rings are in an η6-coordination to the ruthenium centres, which are bridged by two chloride ligands. In addition, the ruthenium centres are bonded to another chloride ligand. The aromatic rings and the Ru2Cl2 four-membered ring enclose a dihedral angle of 55.85 (6)°

Stereochemically Pure Si‐Chiral Aminochlorosilanes

Silicon-based compounds with stereochemical information and convertible functional units are valuable building blocks in synthetic chemistry. Si-stereogenic aminochlorosilanes are built up by Si−N bond formation between an achiral dichlorosilane and a chiral enantiomerically pure primary amine. Both diastereomers could be isolated as stereochemically pure single-crystals by fractional crystallization and were analyzed by X-ray crystallography. Defined intermolecular interaction patterns were identified illustrating the role of N−H⋅⋅⋅π, C−H⋅⋅⋅π, and N−H⋅⋅⋅Cl contacts in the molecular crystalline packing arrangements. Stepwise functionalization of the silicon−chlorine and silicon−amine functions was carried out, demonstrating their potential for use as a chiral synthesis precursors. Via optically pure aminomethoxysilanes, enantiomerically enriched methoxysilanols, chloromethoxysilanes, and methoxysilanethiols were synthesized. The stereospecificity of the transformations was monitored. The (R)-BINOL-PSSLi method for determining the enantiomeric purity was found to be the tool of choice for acid-sensitive silanols and silanethiols

Coordinación de un fragmento organometálico de 12 electrones al anillo aromático de complejos pinza pocop / tesis que para obtener el grado de Doctorado en Ciencias Químicas, presenta Noel Angel Espinosa Jalapa ; tutor principal de tesis Ronan Le Lagadec Hays

. 221 páginas : ilustraciones. Doctorado en Ciencias Químicas Universidad Nacional Autónoma de México, 2013 Programa de Posgrado en Ciencias Química

Controlled Synthesis and Molecular Structures of Methoxy-, Amino-, and Chloro-Functionalized Disiloxane Building Blocks

Functionalized disiloxane units with defined structures are interesting molecular models for investigating the reactivity and chemoselectivity in transformations that are of interest in synthesis, surface chemistry, and materials science. (Mes)PhSi(OMe)(2)(1) (Mes = mesityl) and (Mes)PhSiCl2(5) were chosen as starting compounds for the controlled synthesis of methoxy-, amino-, and chloro-functionalized unsymmetric disiloxanes. Two synthesis routes towards (Mes)PhSi(OMe)(OSiPh3) (3) were followed, one via the aminomethoxysilane (Mes)PhSi(OMe)(NC4H8) (2) and the other via the chlorodisiloxane (Mes)PhSiCl(OSiPh3) (6). The amino-substituted disiloxane (Mes)PhSi(NC4H8)(OSiPh3) (4) was obtained from the chloro derivative6withN-pyrrolidinyllithium, but the same reaction starting from compound3was not successful. All provided disiloxanes were structurally characterized by X-ray crystallography

Hidden silylium-type reactivity of a siloxane-based phosphonium–hydroborate ion pair

A new class of siloxane-based cations with hidden silylium-type reactivity is provided, which, in combination with an arylborate counteranion, initiates a highly selective para-C(sp(2))-F defunctionalization of a perfluorinated aryl group. The hydrodefluorinated aryl borane is obtained as a crystalline solid via continuous sublimation during the reaction. The heterocyclic six-membered cation could be obtained single-crystalline after dehydrogenative anion exchange. DFT calculations give insight into the bonding within the siloxane-based cation and the mechanism of the ion pair reaction

Functional Group Variation in tert ‐Butyldiphenylsilanes (TBDPS): Syntheses, Reactivities, and Effects on the Intermolecular Interaction Pattern in the Molecular Crystalline State

We present the preparation of tert-butyldiphenylsilanes differing in one functional group. The molecular structures of the phenyl (3), methoxy (4), and amino derivatives (5) were elucidated by single-crystal X-ray diffraction analysis and their crystal packing investigated by Hirshfeld surface analysis along with 2D fingerprint plots. In the all-C derivative 3, the high symmetry dependence of the crystal packing enables a multitude of directional C(methyl)−H⋅⋅⋅C(π) interactions between the tert-butyl and phenyl groups. The methoxy derivative 4 is characterized by considerably short H⋅⋅⋅H contacts possibly resulting from pre-orienting C(aryl)−H⋅⋅⋅O and C(aryl)−H⋅⋅⋅C(π) hydrogen bonds. In the amino derivative 5, the nitrogen atom is not involved in intermolecular interactions, instead dispersive H⋅⋅⋅H contacts might become more important for the crystal cohesion. These findings once again underline the pronounced lone electron pair density transfer from the nitrogen atom towards the silicon atom