Silicone elastomers are normally thermosets, which are not readily recycled or repurposed. The few examples of thermoplastic silicone elastomers depend on reversible covalent and non-covalent molecular interactions. It is demonstrated that amine-boronate complex formation provides a simple and flexible route to reversible crosslinked silicones. A variety of network structures were prepared by use of terminal and pendantly functionalised silicone boronates and amines. The crosslink density was quantified using a combination of Shore-hardness measurements, swelling, and rheological analyses. Stress induced by compressive force could be relieved through dynamic B-N bond reformation at 60 °C. Materials could be fully disassembled through introduction of n-butylamine and successfully reformed upon removal of the monofunctional amine by evaporation.
Lithiation of BF 3-complexed dimethylaminoferrocene occurs exclusively ortho to the dimethylamino group in the cyclopentadienyl ring providing structurally diverse products in 76-94% yield after electrophile quench. This method represents the first direct C2-lithiation of a monosubstituted aminoferrocene, offering rapid and complementary access to this class of compounds over procedures that utilize carbon- and sulfur-based directing groups and may serve as a prelude to an asymmetric process.
A new class of surface-active compounds based on the combination of silicones and boronic acids is described. The properties of the compounds can be tuned by manipulation of both the hydrophobic (silicone size and 3D structure) and hydrophilic components (by binding different saccharides to the boronic acid). Stabilization of the four-coordinate boron structure is provided by Tris buffer that also maintains neutral pH to suppress silicone hydrolysis.
A series of PdCl 2 , PtCl 2 , and Ir(COD)BAr F complexes bearing a rare class of racemic bidentate 2-phosphino-1-dimethylaminoferrocene ligands were prepared and characterized by NMR spectroscopy and X-ray crystallography. The new complexes displayed a structural trend relating a decrease in heteroatom-metal bond length with an increase in ligand bite angle on going from Ir to Pd and Pt. The PdCl 2 and PtCl 2 complexes were almost isostructural and featured MCl 2 moieties in the plane of the substituted Cp ring of the ligand. In contrast, the Ir(COD) þ complex was distinguished by a bend of the Ir(COD) moiety toward the unsubstituted (Cp 0 ) ring. The latter gave rise to a steric interaction that placed the Cp rings in almost eclipsed conformations. Ligand 8a (2-diphenylphosphino-1-dimethylaminoferrocene) was able to promote Pd-catalyzed Suzuki-Miyaura and Buchwald-Hartwig coupling of aryl chlorides in addition to Ir-catalyzed hydrogenation of electron-deficient and unactivated alkenes. A preliminary intramolecular hydroamination of a terminal alkene using 8a in conjunction with Ir(I) afforded the cyclized product in 64% yield.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.