Parathion Hydrolysis Revisited: In Situ Aqueous Kinetics by \u3csup\u3e1\u3c/sup\u3e H NMR

The kinetics of parathion (PTH) decomposition into para-nitrophenolate (pNP) and O,O-diethylthiophosphate (DETP) were measured in high-pH aqueous solutions at 20 °C by proton nuclear magnetic resonance spectroscopy (1H NMR). Reaction rates were determined over a 16 h observation time, in solutions with NaOD concentrations of 5.33 mM, 33.33 mM, and 100 mM, with NaCl added to fix ionicity. The pseudo-first-order rate constants for these systems were determined to be 1.9 × 10–4 min–1, 1.4 × 10–3 min–1, and 3.8 × 10–3 min–1 respectively. The slope of the linear plot of these rates against OD– concentration yielded the second-order hydrolysis rate constant 3.90 × 10–5 mM–1 min–1, valid over this pH range from 10.5 to 13. The data agree with some, and contradict other, earlier work. Our fitting procedure included background levels and allowed us to not only obtain reliable kinetic results but also to measure residual pNP and DETP impurity levels

Examining the Impact of Steric and Electronic Variation in N\u3csub\u3e2\u3c/sub\u3eS Scorpionate Ligands on the Properties of Zinc(II) and Cadmium(II) Complexes

A series of LZn(II)Br (1–4) and LCd(II)Cl complexes (9–11) has been prepared by the reaction of metal halide precursors with the lithium salts of the N2S− ligands bis(3,5-diisopropylpyrazol-1-yl)dithioacetate (L1), bis(3,5-di-tert-butylpyrazol-1-yl)dithioacetate (L2), N-phenyl-2,2-bis(3,5-diisopropylpyrazol-1-yl)thioacetamide (L3) and N-phenyl-2,2-bis(3,5-di-tert-butylpyrazol-1-yl)thioacetamide (L4). Characterization by X-ray crystallography and DOSY NMR studies indicate that LZnBr complexes 1–4 are mononuclear both in the solid state and in solution. Steric differences between ligands L1–L4 result in distortion from an ideal tetrahedral geometry for each complex, with the degree of distortion depending on the bulk of the ligand substituents. In contrast, the related complex L3CdCl was shown by X-ray crystallography to dimerize in the solid state to form the chloride-bridged five-coordinate complex [L3CdCl]2 (10). Despite 10 having a dinuclear structure in the solid state, DOSY NMR studies indicate 9–11 exist as mononuclear LCdCl species in solution. In addition, Zn(II) cyanide complexes of the form LZnCN [L = L1 (5), L3 (7), L4 (8)] have been characterized and the X-ray structure of 8 determined. Moreover, density functional theory calculations have been conducted which yield important insight into the bonding in 1–4 and 5–8 and the electronic impact of ligands L1–L4 on the zinc(II) ion and its ability to function as a Lewis acid catalyst