T:Toxic;7440-38-2Relevant articles and documents
Pnictogen-hydride activation by (silox)3Ta (silox = tBu3SiO); Attempts to circumvent the constraints of orbital symmetry in N2 activation
Hulley, Elliott B.,Bonanno, Jeffrey B.,Wolczanski, Peter T.,Cundari, Thomas R.,Lobkovsky, Emil B.
, p. 8524 - 8544 (2010/12/18)
Activation of N2 by (silox)3Ta (1, silox = tBu3SiO) to afford (silox)3Ta=N-N=Ta(silox) 3 (12-N2) does not occur despite ΔG°cald = -55.6 kcal/mol because of constraints of orbital symmetry, prompting efforts at an independent synthesis that included a study of REH2 activation (E = N, P, As). Oxidative addition of REH 2 to 1 afforded (silox)3HTaEHR (2-NHR, R = H, Me, nBu, C6H4-p-X (X = H, Me, NMe2); 2-PHR, R = H, Ph; 2-AsHR, R = H, Ph), which underwent 1,2-H2- elimination to form (silox)3Ta=NR (1=NR; R = H, Me, nBu, C6H4-p-X (X = H (X-ray), Me, NMe2, CF 3)), (silox)3Ta=PR (1=PR; R = H, Ph), and (silox) 3Ta=AsR (1=AsR; R = H, Ph). Kinetics revealed NH bond-breaking as critical, and As > N > P rates for (silox)3HTaEHPh (2-EHPh) were attributed to (1) ΔG°calc(N) calc(P) ～ ΔG°calc(As); (2) similar fractional reaction coordinates (RCs), but with RC shorter for N P～As. Calculations of the pnictidenes aided interpretation of UV-vis spectra. Addition of H2NNH2 or H2N-N(cNC2H3Me) to 1 afforded 1=NH, obviating these routes to 12-N2, and formation of (silox)3MeTaNHNH2 (4-NHNH2) and (silox) 3MeTaNH(-cNCHMeCH2) (4-NH(azir)) occurred upon exposure to (silox)3Ta=CH2 (1=CH2). Thermolyses of 4-NHNH2 and 4-NH(azir) yielded [(silox)2TaMe](μ- NαHNβ)(μ-NγHN δH)[Ta(silox)2] (5) and [(silox)3MeTa] (μ-η2-N,N: η1-C-NHNHCH2CH 2CH2)[Ta(κ-O,C-OSitBu2CMe 2CH2)(silox)2] (7, X-ray), respectively. (silox)3Ta=CPPh3 (1=CPPh3, X-ray) was a byproduct from Ph3PCH2 treatment of 1 to give 1=CH 2. Addition of Na(silox) to [(THF)2Cl3Ta] 2(μ-N2) led to [(silox)2ClTa](μ-N 2) (8-Cl), and via subsequent methylation, [(silox) 2MeTa]2(μ-N2) (8-Me); both dimers were thermally stable. Orbital symmetry requirements for N2 capture by 1 and pertinent calculations are given.
Synthesis of volatile inorganic hydrides by electrochemical method
Turygin,Tomilov,Berezkin, M. Yu.,Fedorov
, p. 1459 - 1478 (2011/02/28)
Published data and results of our investigations on the problem of electrochemical synthesis of arsenic, phosphorus, and germanium hydrides are generalized. The results of the developments of the physicochemical bases of arsine synthesis by electrochemical reduction of arsenic acid, phosphine by reduction of white phosphorus in organic solvents, and monogermane by reduction of germanate in basic conditions are reported. The current yield of hydrides is 95, 90, and 40%, respectively. The promising guidelines of the practical use of electrochemical methods of the synthesis of the hydrides in the manufacture of semiconductor materials for microelectronics, optics, and laser engineering are discussed. The development of an arsine generator attracts considerable interest, which can serve as a basis for an aggregative continuous apparatus used in complex flow charts of manufacture of semiconductor materials.
Spectrophotometric determination of arsenic via nanogold formation in micellar medium
Pal, Anjali,Maji, Sanjoy Kumar
, p. 1178 - 1182 (2007/10/03)
Colloidal gold nanoparticles are formed in aqueous anionic micellar medium by the quantitative reduction of chloroauric acid (HAuCl4) by arsine (AsH3) gas produced from arsenic bearing sample water. The absorbance of the pink gold sol (λmax at 530 nm) is a measure of arsenic concentration present in the sample. Both, As(III) and As(V) either present individually or in mixture could be determined. The molar absorptivity is 6.1×103 lit mol-1 cm-1 and the Sandell sensitivity is 1.28×10-2 μg cm-2. The gold particles, as observed from the transmission electron microscopy analysis, are spherical in nature, the average size being 14±5 nm. The linear dynamic range (LDR) for the arsenic determination is 0-0.5 ppm (0-6.67×10 -6 M). The limit of detection (LOD) is 0.005 ppm. The 95% confidence limit for 0.2 ppm of arsenic is 0.207±0.007 ppm (for 10 replicates). The relative standard deviation (RSD) is 2+/Fe3+, Ca2+/Mg 2+, PO4-3, SiO3-2, NO3-, Cl-, SO4-2, humic acid, common herbicides/pesticides like 2,4-D, endosulfan, atrazine, etc. and can be applied for the determination of total arsenic concentration in real water samples. The results are in good agreement with the SDDC method. The toxic and volatile organic solvents used for silver diethyldithiocarbamate method could be avoided in this method and hence it is safer, much easier and more reproducible.
