N-phosphanylamidine ligands and their catalytic activity in the hydroformylation of 1-octene and styrene

Pyridine-based N-phosphanylamidine ligands i-Pr₂N-C(pyr)N-PR₂ (R = Ph (3), i-Pr (4)) were synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Mononuclear rhodium complexes 7 and 8 were obtained in one step from the [RhCl(COD)]₂ dimer and the monodentate ligands 1 and 2. Their single-crystal X-ray diffraction studies revealed the structural adaptive behavior of the monodentate N-phosphanylamidine ligands 1 and 2 upon k¹-P coordination mode in rhodium(I) complexes with the imino nitrogen atom of the amidine function which behaves as a “universal joint”. Compounds 1-4 were evaluated as ligands in the 1-octene and styrene hydroformylation reactions. The results obtained are encouraging and represent the first report on the use of N-phosphanylamidine ligands of the type R″₂N-C(R′)N-PR₂ in catalytic reactions.     

Complexes with metal-carbon bonds,part III(1). Preparation and properties of binuclear diarylplatinum(II) compounds

Summary Reaction ofcis-PtCl₂(R₂S)₂, where R=Et, n-Pr or i-Pr, with an excess of PhLi orp-tolylLi in ether yielded the dimeric [PtR₂(R₂S)]₂ complexes where R=Ph orp-tolyl. Usingtrans-PtCl₂(R₂S)₂ under the same conditions with PhLi, both [PtPh₂(Et₂S)]₂ and PtPh₂(Et₂S)₂ were isolated.The dimericcis-[PtR₂(Et₂S)]₂ complexes reacted with a range of neutral ligands to give PtR₂L₂ where L=Et₂S, Me₂S, PPh₃, t-BuNC, 0.5 (bipyridine) or pyridine. With CO, thecis-PtR₂(Et₂S)(CO) compounds were formed. Thecis-Pt(C₆F₅)₂(Et₂S)₂ complex reacted stepwise with PPh₃ and both Pt(C₆F₅)₂(Et₂S)(PPh₃) and Pt(C₆F₅)₂(PPh₃)₂ were isolated.     

Anomalous temperature dependence of sub-critical crack growth in silica glass

The effects of temperature, water vapor, and stress on the rate of sub-critical crack growth (SCG) in fused silica are reported. The crack velocity was measured using the double-cleavage-drilled compression method. In contrast to other inorganic oxide glasses, crack growth velocities (in region I) were found to decrease with increase in temperature. Hence a small temperature rise has the apparent effect of improving the mechanical strength of a stressed-glass part. Despite the anomalous temperature dependence, SCG in fused silica is still likely governed by the established water-enhanced stress-corrosion mechanism; another competing phenomenon is proposed to cause the observed temperature dependence. Measured crack velocities are described using an empirical model (for region I) and a mass-transport model limited by Knudsen diffusion (for region II).     

Simply-transitive homothety groups

In this paper the spin-coefficient formalism of Penrose and Rindler is applied to the problem of finding space-times that admit a simply-transitive group of homotheties. The method is illustrated by an application to algebraically special vacuum space-times. Vacuum metrics with a fivedimensional homothety group are also considered.     

Sorption of arsenic, cadmium, and lead by chars produced from fast pyrolysis of wood and bark during bio-oil production

Bio-char by-products from fast wood/bark pyrolyses, were investigated as adsorbents for the removal of the toxic metals (As(3+), Cd(2+), Pb(2+)) from water. Oak bark, pine bark, oak wood, and pine wood chars were obtained from fast pyrolysis at 400 and 450 degrees C in an auger-fed reactor and characterized. A commercial activated carbon was also investigated for comparison. Chars were sieved (>600, 600-250, 250-177, 177-149, and <149 microm) and the particle size fraction from 600 to 250 microm was used without further modification for all studies unless otherwise stated. Sorption studies were performed at different temperatures, pHs, and solid to liquid ratios in the batch mode. Maximum adsorption occurred over a pH range 3-4 for arsenic and 4-5 for lead and cadmium. Kinetic studies yielded an optimum equilibrium time of 24 h with an adsorbent dose of 10 g/L and concentration approximately 100 mg/L for lead and cadmium. Sorption isotherms studies were conducted in broad concentration ranges (1-1000 ppb for arsenic, 1x10(-5)-5x10(-3) M for lead and cadmium). Oak bark out-performed the other chars and nearly mimicked Calgon F-400 adsorption for lead and cadmium. In an aqueous lead solution with initial concentration of 4.8x10(-4) M, both oak bark and Calgon F-400 (10 g/L) removed nearly 100% of the heavy metal. Oak bark (10 g/L) also removed about 70% of arsenic and 50% of cadmium from aqueous solutions. Varying temperatures (e.g., 5, 25, and 40 degrees C) were used to determine the effect of temperatures. The equilibrium data were modeled with the help of Langmuir and Freundlich equations. Overall, the data are well fitted with both the models, with a slight advantage for Langmuir model. The oak bark char's ability to remove Pb(II) and Cd(II) is remarkable when considered in terms of the amount of metal adsorbed per unit surface area (0.5157 mg/m(2) for Pb(II) and 0.213 mg/m(2) for Cd(II) versus that of commercial activated carbon.     

The solution of the vibrational problem in Cartesian displacement coordinates and the use of the eigenvectors in Coriolis and transition moment calculations

The Meal and Polo Coriolis constant formula and the Gribov intensity theory are rested in terms of the eigenvectors of the $\text{(BM}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{t}}\text{F(BM}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{)}$ matrix. Advantages stem from elimination of L^?1 and G^?1 from the formulations. Some symmetry properties of the Coriolis matrix are discussed.