Initiation of Olefin Metathesis: Reaction of Deca-2,8-diene with Catalysts formed from Me_4Sn-WC1_6 and Me_3Al_2Cl_3-(Ph_3P)_2(NO)_2Cl_2Mo

The initial product of the metathesis of deca-2,8-diene with metathesis catalysts formed from either Me_4Sn–WCl_6 or Me_3Al_2Cl_3–(Ph_3P)_2(NO)_2Cl_2Mo is propene; labelling of the terminal groups of the diene and the alkylating agents gives a labelling pattern in the propene that is best explained in terms of generation of a carbene in the initiation step from the alkylating agent

Synthesis of neutral nickel catalysts for ethylene polymerization – the influence of ligand size on catalyst stability

A facile synthesis of nickel salicylaldimine complexes with labile dissociating ligands is described. In addition to producing highly active ethylene polymerization catalysts, important insights into the effect of ligand size on catalyst stability and information on the mechanism of polymerization are provided

A New Ruthenium-Based Olefin Metathesis Catalyst Coordinated with 1,3-Dimesityl-1,4,5,6-tetrahydropyrimidin-2-ylidene: Synthesis, X-ray Structure, and Reactivity

The new ruthenium olefin metathesis catalyst 4 bearing a 5,5‘-dimethyl-1,3-dimesityl-1,4,5,6-tetrahydropyrimidin-2-ylidene ligand was first synthesized from (PCy_3)_2(Cl)_2Ru ═ CHPh (1). The X-ray crystal structure of complex 4 has been determined and shows that the N-mesityl group of the six-membered carbene ligand and the benzylidene moiety are in close proximity (2.9 Å). This catalyst demonstrates moderate reactivity for both ring-closing olefin metathesis and ring-opening metathesis polymerization

Insights into the Deactivation of Neutral Nickel Ethylene Polymerization Catalysts in the Presence of Functionalized Olefins

A study on the products of reaction between a neutral nickel(II) olefin polymerization catalyst and methyl acrylate is presented. A deactivation mechanism involving hydrogen transfer from substrate to catalyst is suggested

Ruthenium-Olefin Complexes: Effect of Ligand Variation upon Geometry

The development of a model system to study ruthenium-olefin complexes relevant to the mechanism of olefin metathesis has been reported recently. Upon addition of the ligand precursor 1,2-divinylbenzene to [RuCl2(Py)2(H2IMes)(CHPh)] (H2IMes=1,3-dimesityl-4,5-dihydroimidazol-2-ylidene), two ruthenium-olefin adducts are formed. Based on 1H NMR spectroscopy experiments and X-ray crystallographic analysis, these complexes are assigned as side-bound isomers in which the olefin and H2IMes ligands are coordinated cis to each other. Herein is reported an investigation of the generality of these observations through variation of the N-heterocyclic carbene ligand and the ligand precursor

On the motion of hairy black holes in Einstein-Maxwell-dilaton theories

Starting from the static, spherically symmetric black hole solutions in massless Einstein-Maxwell-dilaton (EMD) theories, we build a "skeleton" action, that is, we phenomenologically replace black holes by an appropriate effective point particle action, which is well suited to the formal treatment of the many-body problem in EMD theories. We find that, depending crucially on the value of their scalar cosmological environment, black holes can undergo steep "scalarization" transitions, inducing large deviations to the general relativistic two-body dynamics, as shown, for example, when computing the first post-Keplerian Lagrangian of EMD theories

Synthesis and Cell Adhesive Properties of Linear and Cyclic RGD Functionalized Polynorbornene Thin Films

Described herein is the efficient synthesis and evaluation of bioactive arginine-glycine-aspartic acid (RGD) functionalized polynorbornene-based materials for cell adhesion and spreading. Polynorbornenes containing either linear or cyclic RGD peptides were synthesized by ring-opening metathesis polymerization (ROMP) using the well-defined ruthenium initiator [(H_(2)IMes)(pyr)_(2)(Cl)_(2)Ru═CHPh]. The random copolymerization of three separate norbornene monomers allowed for the incorporation of water-soluble polyethylene glycol (PEG) moieties, RGD cell recognition motifs, and primary amines for postpolymerization cross-linking. Following polymer synthesis, thin-film hydrogels were formed by cross-linking with bis(sulfosuccinimidyl) suberate (BS^3), and the ability of these materials to support human umbilical vein endothelial cell (HUVEC) adhesion and spreading was evaluated and quantified. When compared to control polymers containing either no peptide or a scrambled RDG peptide, polymers with linear or cyclic RGD at varying concentrations displayed excellent cell adhesive properties in both serum-supplemented and serum-free media. Polymers with cyclic RGD side chains maintained cell adhesion and exhibited comparable integrin binding at a 100-fold lower concentration than those carrying linear RGD peptides. The precise control of monomer incorporation enabled by ROMP allows for quantification of the impact of RGD structure and concentration on cell adhesion and spreading. The results presented here will serve to guide future efforts for the design of RGD functionalized materials with applications in surgery, tissue engineering, and regenerative medicine