Kinetics and mechanism of the photolytic CO-substitutions of cyclopentadienyl(dicarbonyl)iron thiocarboxylate complexes,Cp′Fe(CO)2SCOR (Cp′ = C5H5, ButC5H4,1,3-Bu2tC5H3; R = alkyl,aryl)

The kinetics of the photolytic CO-substitution of CpFe(CO)₂SCOR [Cp = C₅H₅, Bu ^t C₅H₄, 1,3-Bu₂ ^t C₅H₃; R = Me, Bu ^t , Ph, 2-(O₂N)C₆H₄, 3-(O₂N)C₆H₄, 4-(O₂N)C₆H₄, 3,5-(O₂N)₂C₆H₃] with PPh₃ were studied in CH₂Cl₂ at 0 °C by i.r. spectroscopy. The reactions yielded exclusively the mono-CO-substituted derivatives, CpFe-(CO)(PPh₃) SCOR, and were found to follow second order kinetics with first order dependence on the concentration of each reactant. The differences in rates are discussed in terms of current knowledge pertaining to such reactions. An associative mechanism is proposed to account for the kinetic data of the reactions described.     

Synthesis and Assessment of Two Malonyl Dihydrazide Derivatives as Corrosion Inhibitors for Carbon Steel in Acidic Media: Experimental and Theoretical Studies

Despite the extensive use of carbon steel in all industrial sectors, particularly in the petroleum industry, its low corrosion resistance is an ongoing problem for these industries. In the current work, two malonyl dihydrazide derivatives, namely 2,2’-malonylbis (N-phenylhydrazine-1-carbothiamide (MBC) and N’1, N’3-bis(-2-hydroxybenzylidene) malonohydrazide (HBM), were examined as inhibitors for the carbon steel corrosion in 1.0 M HCl. Both MBC and HBM were characterised using thin-layer chromatography, elemental analysis, infrared spectroscopy, and nuclear magnetic resonance techniques. The corrosion tests were performed using mass loss measurements, polarisation curves, and electrochemical impedance spectroscopy. It is obtained from the mass loss studies that the optimal concentration for both inhibitors is 2.0 × 10⁻⁵ mol/L, and the inhibition efficiencies reached up to 90.7% and 84.5% for MBC and HBM, respectively. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP) indicate an increased impedance in the presence of both MBC and HBM and mixed-type inhibitors, respectively. Both inhibitors can mitigate corrosion in the range of 298–328 K. Values of free energy changes obtained from the Langmuir model suggest that the inhibitors suppress the corrosion process principally by chemisorption. The computational investigations were conducted to identify the factors connected with the anti-corrosive properties of the examined inhibitors.     

Synthesis and crystal structures of dialkyl[1,1-bis(alkylchloroalanyl)organylmethyl]phosphine•dialkylchloroalane(1/1) complexes

Dialkyl[1,1-bis(alkylchloroalanyl)organylmethyl]phosphine?dialkylchloroalane(1/1) complexes (1a–1d) were synthesized and fully characterized. In 1a–1d, dative bonding between phosphorus or chlorine as a donor atom and aluminum as an acceptor atom results in a bicyclic system. The ³¹P{¹H} NMR spectra of all compounds dissolved in d₆-benzene indicate the presence of several isomers in solution. The ²⁷Al{¹H} NMR spectra of 1a–1d dissolved in d₆-benzene as well show very broad singlets between 177 and 140 ppm. For all compounds, crystal structures consist of two fused four- and five-membered rings. The 1λ³-phosphaalkyne reacts at the Al–C bond of the starting material, whereas the Al–Cl moiety remains intact. The heterocycle isolated is a molecular complex of the underlying insertion compound and a third equivalent of dialkylaluminum chloride. The four- and five-membered rings both contain two chlorine-bridged aluminum atoms, Al3 and Al1, slightly more symmetrical than that between Al1 and Al6. In the four-membered ring the two aluminum atoms Al1 and Al6 approach each other at an average distance of 289.1 pm which tallies with the element–element distance (286.3 pm) in aluminum metal.