Synthesis of a fumed silica-supported poly-3-(2-aminoethylamino)propylsiloxane platinum complex and its catalytic behavior in the hydrosilylation of olefins with triethoxysilane

Short-Chained Platinum Complex Catalyzed Hydrosilylation under Thermomorphic Conditions: Heterogeneous Phase Separation at Ice Temperature

Homogeneous catalysts PtCl₂[5,5'-bis-(n-ClCF₂(CF₂)₃CH₂OCH₂)-2,2'-bpy] (2A) and PtCl₂[5,5'-bis-(n-HCF₂(CF₂)₃CH₂OCH₂)-2,2'-bpy] (2B), which contained short fluorous chains, were synthesized and used in catalysis of hydrosilylation of alkynes. In these reactions the thermomorphic mode was effectively used to recover these catalysts from the reaction mixture up to eight cycles by taking advantage of heterogeneous phase separation at ice temperature. This kind of catalysis had previously been observed in fluorous catalysts of platinum containing about 50% F-content, but in this work the percentage of F-content is decreased to only about 30%, by which we termed them as "very light fluorous". Our new type of catalyst with limited number of F-content is considered as the important discovery in the fluorous technology field as the reduced number of fluorine atoms will help to be able to comply the EPA 8-carbon rule. The metal leaching after the reaction has been examined by ICP-MS, and the testing results show the leaching of residual metal to be minimal. Additionally, comparing these results to our previous work, fluorous chain assisted selectivity has been observed when different fluorous chain lengths of the catalysts are used. It has been found that there exists fluorous chain assisted better selectivity towards β-(E) form in the Pt-catalyzed hydrosilylation of non-symmetric terminal alkyne when the Pt catalyst contains short fluorous chain (i.e., 4 Cs). Phenyl acetylenes showed the opposite regioselectivity due to pi-pi interaction while using the same catalyst via Markovnikov's addition to form terminal vinyl silane, which is then a major product for Pt-catalyzed hydrosilylation of terminal aryl acetylene with triethylsilane. Finally, the kinetic studies indicate that the insertion of alkyne into the Pt-H bond is the rate-determining step.

Formation of functionalized silica-based nanoparticles and their application for extraction and determination of Hg (II) ion in fish samples

An isonicotinic acid hydrazide (INAH) chemically modified fumed silica, as a novel adsorbent, was designed for the preconcentration and determination of Hg (II) ions in fish samples via the solid phase extraction followed by the hydride generation atomic absorption spectrometry (HG-AAS). In this work, the efficiency of the synthesized adsorbent was investigated to determine its ability for the extraction of the Hg (II) ions from the aqueous solutions. The extraction efficiency was investigated by optimizing of different experimental conditions, such as pH, sample volume, flow rate, adsorbent dosage, and eluent type. Under the optimal conditions, a linear calibration curve for the solid phase extraction method was obtained in the range of between 0.12 and 16.5 μg L^-1. The obtained detection limit and preconcentration factor were 0.018 μg L^-1 and 25, respectively (RSD > 3%). The proposed optimized method was successfully applied to fish samples.