The synthesis and characterization of compounds of the type Hg[1-C(6)H(4)-2-C(H)=NC(6)H(5-n)R(n)](2)

The organomercurial compounds Hg[1-C(6)H(4)-2-C(H)=NC(6)H(5-n)R(n)](2) (R = 4-NMe(2), 6a; 4-Me, 6b; 4-I, 6c; 4-NO(2), 6d; 2-(i)Pr, 6e; 2-Me, 6f; 2,6-(i)Pr(2), 6g; 2,6-Me(2), 6h) have been prepared in good overall yield from 2-bromobenzaldehyde. All of the compounds have been characterized by elemental analysis, (1)H NMR, (13)C[(1)H] NMR, and infrared spectroscopy. In addition, compounds 6a [C(30)H(30)HgN(4), triclinic, P, a = 6.20000(10) A, b = 9.2315(2) A, c = 10.9069(3) A, alpha = 85.8510(10) degrees, beta = 89.3570(10) degrees, gamma = 87.206(2) degrees, Z = 1], 6b [C(28)H(24)HgN(2), monoclinic, P2(1)/c, a = 12.8260(5) A, b = 14.0675(4) A, c = 6.1032(2) A, beta = 90.0990(10) degrees, Z = 2], 6g [C(38)H(44)HgN(2), triclinic, P, a = 8.2626(2) A, b = 9.8317(2) A, c = 11.8873(3) A, alpha = 103.6650(10) degrees, beta = 109.3350(10) degrees, gamma = 104.627(2) degrees, Z = 1], and 6h [C(30)H(28)HgN(2), monoclinic, P2(1)/c, a = 12.5307(2) A, b = 10.9852(2) A, c = 18.2112(2) A, beta = 104.0190(10) degrees, gamma = 87.206(2) degrees, Z = 4] have been characterized by low-temperature single-crystal X-ray diffraction studies, and two different molecular geometries about the central mercury atom have been observed; intramolecular contacts suggest a van der Waals radius for Hg of 2.1-2.2 A.     

Synthesis of 6-cyanopurines and the isolation and X-ray structure of novel 2H-pyrroles

(Z)-N¹-(2-Amino-1,2-dicyanovinyl)-N²-substituted-formainidines react with dimethylformamide diethyl acetal at room temperature to give 6-cyanopurines as the major product together with novel 5-amino-2-arylimino-3,4-di[(N,N-dimethylamino)methylideneamino]-2H-pyrroles, which have been fully characterised and a single crystal X-ray analysis has been carried out on the N-phenyl derivative.     

Calculating binary and ternary multiphase equilibria: extensions of the integral area method

The area method was proposed in 1992 to calculate binary and ternary 2-phase equilibria. In its integral form, the method provides both the necessary and sufficient conditions required for the determination of the global minimum reduced Gibbs energy of mixing (Φ). The method has since been applied to the calculation of both pure component and ternary multiphase equilibria in a differential form. However, the extension of the original (2 point) integral area method to the direct calculation of both binary and ternary multiphase equilibria has not been completed. Direct 3 point and modified 2 point search methods have therefore been developed here and used to estimate the phase compositions of a representative binary vapour-liquid-liquid system. The 2 point area method principle has been extended and applied to the calculation of ternary multiphase equilibria using a net volume approach. However, this volume method was found to fail due to an underlying inconsistency in the bounding of the integrated Φ surface by the trial 3-phase region. A new method is proposed that overcomes this problem by minimising the area of intersection between a tangent plane and the Φ surface. This new method has successfully calculated the 3-phase compositions of two simple test systems from a variety of initial mixture starting points.     

Rapid determination of radiostrontium in seawater samples

A new method for the determination of radiostrontium in seawater samples has been developed at the Savannah River National Laboratory (SRNL) that allows rapid pre-concentration and separation of strontium and yttrium isotopes in seawater samples for measurement. The new SRNL method employs a novel and effective pre-concentration step that utilizes a blend of calcium phosphate with iron hydroxide to collect both strontium and yttrium rapidly from the seawater matrix with enhanced chemical yields. The pre-concentration steps, in combination with rapid Sr Resin and DGA Resin cartridge separation options using vacuum box technology, allow seawater samples up to 10 L to be analyzed. The total ⁸⁹Sr + ⁹⁰Sr activity may be determined by gas flow proportional counting and recounted after ingrowth of ⁹⁰Y to differentiate ⁸⁹Sr from ⁹⁰Sr. Gas flow proportional counting provides a lower method detection limit than liquid scintillation or Cerenkov counting and allows simultaneous counting of samples. Simultaneous counting allows for longer count times and lower method detection limits without handling very large aliquots of seawater. Seawater samples up to 6 L may be analyzed using Sr Resin for ⁸⁹Sr and ⁹⁰Sr with a minimum detectable activity (MDA) of 1–10 mBq/L, depending on count times. Seawater samples up to 10 L may be analyzed for ⁹⁰Sr using a DGA Resin method via collection and purification of ⁹⁰Y only. If ⁸⁹Sr and other fission products are present, then ⁹¹Y (beta energy 1.55 MeV, 58.5 day half-life) is also likely to be present. ⁹¹Y interferes with attempts to collect ⁹⁰Y directly from the seawater sample without initial purification of Sr isotopes first and ⁹⁰Y ingrowth. The DGA Resin option can be used to determine ⁹⁰Sr, and if ⁹¹Y is also present, an ingrowth option with using DGA Resin again to collect ⁹⁰Y can be performed. An MDA for ⁹⁰Sr of <1 mBq/L for an 8 h count may be obtained using 10 L seawater sample aliquots.     

Experimental and Computational Evidence for the Mechanism of Intradiol Catechol Dioxygenation by Non‐Heme Iron(III) Complexes

Catechol intradiol dioxygenation is a unique reaction catalyzed by iron‐dependent enzymes and non‐heme iron(III) complexes. The mechanism by which these systems activate dioxygen in this important metabolic process remains controversial. Using a combination of kinetic measurements and computational modelling of multiple iron(III) catecholato complexes, we have elucidated the catechol cleavage mechanism and show that oxygen binds the iron center by partial dissociation of the substrate from the iron complex. The iron(III) superoxide complex that is formed subsequently attacks the carbon atom of the substrate by a rate‐determining C?O bond formation step.     

Modeling the Synthesis of Butyl Methacrylate Macromonomer by Sequential ATRP‐CCTP

The atom transfer radical polymerization of butyl methacrylate mediated by Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine in anisole at 70 °C with the subsequent addition of bis(difluoroboryldiphenylglyoximato)cobalt(II) after 2 h is modeled using Predici software, to gain additional insight to the system used experimentally to produce macromonomer chains with narrow dispersity. The mechanistic model, using kinetic coefficients from the literature and activation and deactivation rate coefficients estimated from this work, provides a good representation of experimental results. The simulations demonstrate that the time (conversion) at which cobalt chain transfer agent is added to the system is critical to control the number‐average molar mass of the final product and also confirm that chains of higher length in the final product are more likely to be nonfunctionalized, in agreement with experimental observations. The model predicts the production of a significant fraction of macromonomer oligomers with lengths of 1–3 units, also consistent with experiments.     

Sulfinate and Carbene Co‐catalyzed Rauhut–Currier Reaction for Enantioselective Access to Azepino[1,2‐a]indoles

A carbene and sulfinate co‐catalyzed intermolecular Rauhut–Currier reaction between enals and nitrovinyl indoles is disclosed. The carbene catalyst activates the enal and the sulfinate co‐catalyst activates the nitrovinyl indole. Both activation processes are realized via the formation of covalent bonds between the catalysts and substrates to generate catalyst‐bound intermediates. The dual catalytic reaction affords azepino[1,2‐a]indole products with excellent stereoselectivity. Our study demonstrates the unique involvement of sulfinate as an effective nucleophilic catalyst in activating electron‐deficient alkenes for asymmetric reactions. This dual catalytic approach should also encourage future explorations of both sulfinate and carbene catalysts for new reactions.     

Reactive Dimerization of an N‐Heterocyclic Plumbylene: C−H Activation with PbII

The N‐heterocyclic plumbylene [Fe{(η⁵‐C₅H₄)NSiMe₃}₂Pb:] is in equilibrium with an unprecedented dimer in solution, whose formation involves the cleavage of a strong C?H bond and concomitant formation of a Pb?C and an N?H bond. According to a mechanistic DFT assessment, dimer formation does not involve direct Pb^II insertion into a cyclopentadienyl C?H bond, but is best described as an electrophilic substitution. The bulkier plumbylene [Fe{(η⁵‐C₅H₄)NSitBuMe₂}₂Pb:] shows no dimerization, but compensates its electrophilicity by the formation of an intramolecular Fe?Pb bond.     

Proton spin relaxation in some paramagnetic transition-metal acetylacetonate complexes. Comparison between theory and experiment

Proton spin-lattice (T₁) and spin-spin (T₂) relaxation times have been measured for CH₃ protons in a series of paramagnetic transition-metal acetylacetonate complexes and the results interpreted in terms of current relaxation theory, τ_r, the correlation time for molecular reorientation, was estimated from the ¹³C T₁ in the analogous diamagnetic Co(III) and Pd(II) complexes. Using this approach and treating in detail the effects of fast CH₃ group internal motion good agreement is obtained between theory and experiment. In all cases electron-nuclear dipolar coupling dominates T₁ whereas the hyperfine contribution can be important for T₂.