NMR linewidth study of a latex interpenetrating network

Polymer structure developed in latex particles has been investigated by measuring the temperature dependence of the carbon magnetic resonance (CMR) peak linewidths. Interpenetrating polymer networks (IPN) were formed by a continuous-addition emulsion polymerization process, in which a crosslinked seed particle was the site for formation of a linear second-stage polymer. Morphology was controlled by the level of crosslinking in the seed stage. The two polymers of the composite particle differ in their glass-transition temperatures by 100°C. By heating the particles to 50°C above the glass-transition temperature of the softer polymer, which formed the continuous network phase of this composite, it was possible to observe its CMR spectrum independently of the other polymer. The temperature dependence of the linewidth varied with the structure of the network. This was characterized by limiting linewidth behavior at both low and high temperature, which systematically varied as a function of the degree of mixing the two phases. Differential scanning calorimetry and electron microscopy corroborated the morphology change observed with the linewidth data. The influence of a diluent, present during formation of the network stage, was also examined with this CMR approach.     

Stepwise reduction of the thiocarbonyl ligand: hydride transfer to CS: thioformyl,thioformaldehyde, methylthiolato,secondary carbene,formyl and iminoformyl complexes of osmium

The complexes OsHX(CS)L(PPh₃)₂ (X  Cl, Br; L  CO and X  Cl; L  CN-p-tolyl), which contain mutually cis hydrido and thiocarbonyl ligands, undergo transfer of the hydrido ligand to CS when treated with CO to give blue complexes containing the thioformyl ligand [OsCHS]. OsCl(CHS)(CO)₂(PPh₃)₂ reacts with borohydride to give the first metal complex of the thioformaldehyde monomer, viz. Os(η²-CH₂S)(CO)₂(PPh₃)₂, which reacts rapidly with HCl to give OsCl(SCH₃)(CO)₂(PPh₃)₂ and then, by a slower reaction, OsCl₂(CO)₂(PPh₃)₂ and CH₃SH. The ligands produced in this stepwise reduction have possible relevance as models for postulated intermediates in the Fischer—Tropsch synthesis. Synthetic routes to formyl [OsCHO], iminoformyl [OsCHNMe] and secondary carbene complexes [OsCHSMe, OsCHNMe₂, OsCHOMe] are also demonstrated.     

Dihapto-acyl derivatives of ruthenium(II). Preparation and structure of Ru[η2-C(O)CH3] I(CO)(PPh3)2 and Ru[η2-C(O)p-tolyl]I(C0) (PPh3) 2

Reaction between Ru(CO)₂(PPh₃)₃ and MeHgI yields Ru[η²-C(O)CH₃]I(CO)(PPh₃)₂ which in solution exists mainly as RuCH₃I(CO)₂(PPh₃)₂ and crystal structure determination of Ru[η²-C(O)CH₃]I(CO)(PPh₃)₂ and previously described Ru[η²-C(O)p-tolyl]I(CO) (PPh₃)₂ confirms that in the solid state both molecules contain dihapto-acyl ligands.     

Direct observation of thiolate displacement reactions on Au(111): the role of physisorbed disulfides

Line-of-sight mass spectroscopy (LOSMS) has been used to study the displacement reaction of ( radical3x radical3)R30 degrees methylthiolate on Au(111) by butylthiolate. The reaction was carried out at room temperature and constant saturation coverage, by exposing the methylthiolate-covered surface to dibutyl disulfide gas. The adsorbed methylthiolate was desorbed as dimethyl disulfide and the cross product methylbutyl disulfide, both identified by LOSMS. This shows that reaction occurs between adsorbed thiolates of different chain length at room temperature, while the kinetics indicate that a rapid equilibrium is established between immobile, chemisorbed thiolates, and highly mobile, physisorbed disulfides.     

The tris(triphenylphosphine)osmium zerovalent complexes Os(CO)2(PPh3)3, .Os(CO)(CNR)(PPh3)3, Os(CO)(CS)(PPh3)3, Os(CS)(cNR)(PPh3)3 and derived compounds

Detailed procedures for the syntheses of Os(CO)₂(PPh₃)₃, Os(CO)(CNR)-(PPh₃)₃ (R = p-tolyl), Os(CO)(CS)(PPh₃)₃ and Os(CS)(CNR)(PPh₃)₃, together with the derived complexes Os(CO)₂(CS)(PPh₃)₂, Os(CO)(CS)(CNR)(PPh₃)₂, Os(η²-C₂H₄)(CO)(CNR)(PPh₃)₂, Os(η²-C₂H₄)(CO)(CS)(PPh₃)₂, Os(η²CS₂)(CO)₂-(PPh₃)₂, Os(η²CS₂)(CO)(CS)(PPh₃)₂, Os(η²-CS₂)(CO)(CNR)(PPh₃)₂, Os(η²PhC₂Ph)(CO)₂(PPh₃)₂ and OsH(C2Ph)(CO)₂(PPh₃)₂ are described.