The efficient synthesis of film-forming colloidal nanocomposite particles is described. A 50:50 mass ratio of styrene and n-butyl acrylate is statistically copolymerized using a cationic azo initiator at 60 °C under aqueous emulsion polymerization conditions in the presence of a commercially available glycerol-functionalized ultrafine silica sol. This new formulation leads to the production of copolymer/silica particles with relatively narrow size distributions and a well-defined “core−shell” morphology. These nanocomposite particles contain up to 43% silica by mass, and the silica aggregation efficiency can exceed 95%, so very few nonaggregated silica nanoparticles remain in solution after the in situ copolymerization is conducted. Upon drying these dispersions, highly transparent free-standing nanocomposite films are obtained. Control experiments confirm the importance of using the cationic azo initiator in combination with the glycerol-functionalized silica sol. Moreover, it is also shown that simple admixtures of a film-forming copolymer latex with the glycerol-functionalized silica sol give much more opaque nanocomposite films, while the deliberate addition of excess silica sol prior to nanocomposite film formation leads to extensive film cracking. Thus this in situ copolymerization route appears to offer a decisive advantage for nanocomposite coatings applications.

Ruthenium η 4 -trimethylenemethane complexes containing two different tridentate phosphine ligands have been synthesized. The formation of the complexes using [Ru(η 4 -COD)(η 3 -CH 2 CMeCH 2 ) 2 ] as the metal precursor occurred via elimination of isobutene. An intermediate species has been isolated in which the ligand coordinates with only two phosphorus atoms. Furthermore, protonation of the trimethylenemethane ligand gave rise to a cationic methylallyl complex.

A double-cyclometalated ruthenium complex containing a chiral tripodal phospholane has been prepared by reaction with [Ru(η 4 -COD)(η 3 -methylallyl) 2 ] via elimination of isobutene. The ruthenium−carbon bonds of this compound were reversibly cleaved by H 2 , resulting in an equilibrium between a tri-and a tetrahydride (4 and 5). T 1 relaxation time measurements revealed the nonclassical nature of the fluctuating hydrides. Release of the gas led to complete re-formation of the cyclometalated compound. Reaction of 3 with D 2 afforded D 10 -5, in which six ortho-phenyl protons and four hydrides were replaced by deuterium. Furthermore, diphenylsilane was found to readily insert into one Ru−C bond to form 6, containing a κ 3 -dihydridosilicate fragment. On the basis of deuterium labeling experiments, the fast exchange between the two hydrides was shown to include a reductive elimination/oxidative addition step involving the remaining metalated phenyl group. Again, pressurization of 6 with H 2 resulted in reversible cleavage of the remaining Ru−C bond, yielding the corresponding trihydride 7.

The modular one-pot synthesis of a large family of bi- and tridentate 2,5-dimethyl- and 2,5-diphenyl-substituted phospholanes employs air-stable chiral phospholanium chloride salts and primary amines or NH(4)Cl as starting materials. These were transformed into the C(2)-symmetric dimethyl- and diphenylphospholane ligands, which reacted with [Rh(cod)(2)]BF(4) (cod=1,5-cyclooctadiene) to yield the rhodium complexes [Rh(L)(cod)]BF(4) (L=bisphospholane ligands). The corresponding trisphospholane complexes, 11 and 12, were obtained in high yields (81 and 92%, respectively), and fully characterised by NMR spectroscopy, mass spectrometry and elemental analysis. Whilst in the C(3)-symmetric complex 11, containing the tridentate 2,5-dimethylphospholane, the ligand is bound symmetrically, different coordination behaviour was found for the diphenyl-substituted complex 12, in which the coordination of only two of the three phospholane moieties to the metal centre was observed. A DFT study at the B3PW91 level established minimum energy structures consistent with experimental findings in solution and in the solid state. The non-coordinated phospholane unit present in 12 allowed further modification of the complex through the coordination of Au(I)-X (X=Cl, C(6)F(5) and tris(trifluoromethyl)phenyl ((F)Mes)) fragments to the pendant phosphane. To investigate the potential of the new ligands, the enantioselective hydrogenation of a series of prochiral olefins as benchmark substrates, using isolated Rh complexes as catalysts, was studied. The substrates included methyl esters of three dehydro-α-acetamido acids and two itaconic acid derivatives. In general good to excellent enantioselectivities (of up to >99% ee) were observed. Ligand backbone modification by coordination of bulky Au-X substituents to the free phospholane unit in complex 12 led to an outstanding enhancement of the catalyst performance and there was a clear correlation between the properties of the complex periphery and the enantioselectivity.