Yuri A. Ustynyuk

Synthesis and study of a new diamidodipyrromethane macrocycle. An anion receptor with a high sulfate-to-nitrate binding selectivityElectronic supplementary information (ESI) available: detailed experimental data and UV-vis spectrophotometric titration data. See http://www.rsc.org/suppdata/cc/b4/b403665d/

A new 2,6-diamidopyridinedipyrromethane hybrid macrocycle () has been synthesized that shows a high selectivity for dihydrogen phosphate and hydrogen sulfate relative to nitrate in acetonitrile solution as judged from UV-vis spectrophotometric titrations; this leads to the suggestion that this or related systems might find use in nuclear waste remediation applications requiring the selective removal of hydrogensulfate from nitrate-rich waste mixtures.

Regioselective synthesis of π-complexes of substituted polycyclic aromatic compounds. Experimental (NMR) and theoretical (DFT) studies of η6,η6-haptotropic rearrangements in naphthalenechromiumtricarbonyl complexes☆

A new regioselective method for the synthesis of (η6-naphthalene)chromium tricarbonyl complexes bearing a substituent R in desired positions of either the coordinated or non-coordinated ring was proposed. The kinetics of η6,η6-haptotropic rearrangements (IRHR) was investigated by NMR spectroscopy for ten pairs of isomer complexes (R=D, CH3, Me3Sn, Me3Si and Cl in position 1 or 2 of coordinated or non-coordinated rings). The free activation energies ΔG# fall into a quite narrow range of 28–31 kcal mol−1 and are therefore relatively insensitive to the influence of substituent R whereas equilibrium constants of IRHR change considerably from 0.03 to 17.26 within the compounds investigated. Electron donating (withdrawing) substituents R increase (decrease) the relative thermodynamic stability of the isomers containing a substituent in coordinated rings. The density functional theory method (DFT) with extensive basis set describes quite satisfactory the geometry and the energy of ground states and correctly predict that the least motion route of Cr(CO)3 from one ring to another via the center of the C4a–C8a bond is forbidden. The transition state for the rearrangement of (η6-naphthalene)chromium tricarbonyl has trimethylenemethane structure of C2v-symmetry in which the Cr(CO)3-group is slightly shifted to the ligand periphery. For the monosubstituted naphthalenechromium tricarbonyls thus, there are two reaction channels of the chromium tricarbonyl group slippage between unsubstituted and substituted rings, one of which is practically unperturbed determining the low sensitivity of the rearrangement rate to the effects of ligand substitution even for 1-R substituted complexes. Calculated activation barriers are in a good accordance with the experimentally determined ΔG# values.

Structure of Complexes Formed by Dissolution of Palladium Diacetate in Methanol and Chloroform. In Situ NMR Study

The behavior of palladium diacetate cyclic trimer [Pd(OAc)(2)](3) (1) upon its dissolution in methanol and wet chloroform was studied by (1)H and (13)C NMR including 2D-HSQC and 2D-DOSY techniques. Upon dissolution, trimer 1 reacts with methanol and is completely transformed first into the methoxo complex Pd(3)(μ-OMe)(OAc)(5) (2), which already at -18 °C undergoes a slow exchange of second bridging acetate ligand between the same palladium atoms to form the symmetric dimethoxo complex Pd(3)(μ-OMe)(2)(OAc)(4), the maximum relative concentration of which reaches 20-30 mol % of initial loading trimer 1. Along with the dimethoxo complex, both soluble and insoluble polynuclear palladium clusters are gradually formed at -18 °C, and their total amount reaches up to 60% of the starting Pd(2+) loading. The increase of temperature to 27 °C results in the reduction of palladium(II) to Pd metal by methanol, which is oxidized and transformed into formaldehyde hemiacetal and methyl formate. Upon dissolution in wet chloroform, trimer 1 is reversibly hydrolyzed to the hydroxo complex Pd(3)(μ-OH)(OAc)(5) (10) in ratio 1/10 ≈ 3/1. The temperature decrease and addition of acetic acid shift the equilibrium in this system toward trimer 1, and addition of water shifts it in the opposite direction. Addition of methanol to the equilibrium mixture of 1 and 10 results in the fast exchange of bridging acetate in trimer 1 by the μ-OMe group. Substitution of the μ-OH ligand by μ-OMe in 10 occurs in parallel but more slowly. Complex 2 formed in both cases is more stable in chloroform than in methanol.

Macrocyclic receptor for pertechnetate and perrhenate anions

The design and synthesis of a neutral macrocyclic host that is capable of perrhenate and pertechnetate recognition is described. The anion affinities and underlying coordination modes were estimated by several experimental and theoretical methods including a new technique--reverse (99)Tc NMR titration.

The silafulvene: a potentially stable compound containing a double carbonsilicon bond

Abstract Two conformations of dimethylsilafulvene are calculated via a CNDO/2 procedure. One of them is planar while in the other the CH 3 SiCH 3 plane is perpendicular to the cyclopentadienyl ring plane. The conformation energies differ by 19.8 kcal/mol.

Pyridinedicarboxylic Acid Diamides as Selective Ligands for Extraction and Separation of Trivalent Lanthanides and Actinides: DFT Study

This article presents a general approach to solving the urgent practical problem of separation of 4f-(lanthanides, Ln3+) and 5f-elements (actinides, An3+) very similar in properties based on the DFT quantum-chemical supercomputer simulation of Ln3+ and An3+ complexes with polydentate nitrogen-containing heterocyclic ligands. The method allows to calculate the geometry parameters of ligands and complexes and the metal to ligand binding energies with accuracy, permitting a direct comparison of calculation results with the experimental data, and estimate selectivity factors for separation of Eu3+/Am3+ model pair cations (SFAm/Eu) in extraction experiments on a semi-quantitative level. The applicability of the method and the approach demonstrated by DFT-modeling (nonempirical PBE functional, extended relativistic full-electron basis set) of a large series of diamides of pyridine-2,6-dicarboxylic (dipicolinic) acid (L) with different substituents at the amide nitrogen atoms and in the pyridine cycle, as well as their complexes [LM]3+, (H2O)nM(NO3)3 (n = 3, 4), and LM(NO3)3 (M = Eu, Am). Based on the theoretical analysis a new model is proposed that describes the mechanism of Ln3+ and An3+ extraction in two-phase system highly acidic water solution-organic solvent, according to which the formation of An3+ and Ln3+ complexes occurs at the water/organic interface as a substitution reaction of hydroxonium ion in a cavity of a protonated ligand for the metal cation. Calculation results confirm the experimentally established higher extraction ability of dipicolinic acid diamides containing one aryl and one alkyl substituent at the amide nitrogen atoms compared to the N,N,N′,N′-tetraalkyl diamides (“effect of anomalous aryl strengthening”). Based on the simulation results the structure of the modified ligand L suggested that it should ensure maximum An3+/Ln3separation selectivity in the series of dipicolinic acid diamides.

Catalytic homogeneous hydrogenation of compounds containing X → O semipolar bonds (X = N, S, P) with para-hydrogen as a promising route for preparation of para-water

The quantum-chemical simulation (DFT, PBE, TZ2p basis set) of the mechanism of catalytic hydrogenation of compounds containing R(n)X --> O semipolar bonds (R(n)X = N(2), Me(2)S, C(5)H(5)N, Ph(3)P) on the Wilkinson catalyst (Ph(3)P)(3)RhCl with para-hydrogen showed that this process proceeds with retention of proton nuclear spin correlation, which enables a principal possibility to synthesize para-H(2)O, i.e. the nuclear spin isomer of water with antiparallel proton spins, using this route.

Organometallic Phosphorous and Arsenic Betaines

Publisher Summary This chapter reviews the synthesis, structure, and reactivity of two betaines—(1) (+) E 15 –C–E 14 –X( - ) and (2) (+) E 15 –C–E 14 ( - ), where (E 15 = P, As; E 14 = Si, Ge, Sn; X = C, S). Most of the presently known betaines of the both-named types were obtained by the reaction of phosphorus or arsenic ylides with stable compounds containing E = X bonds (E = C, Si; X = C, S), cyclic oligomers of these compounds (R 2 EX) n (E = Si, Ge, Sn; X = S, n = 2, 3), three- and four-membered silacarbocycles, carbenes or their organoelement analogs. The synthesis of the firstbetaines with carbanionic centers and thiolate centers and the synthesis of the second betaines are discussed. . The most important geometric parameters obtained by the X-ray diffraction study of first and second betaines are also presented. Multinuclear NMR spectroscopy is a very informative and reliable method for the identification and study of betaines in solutions. The main NMR parameters of these compounds are presented.

Predictive Models for HOMO and LUMO Energies of N-Donor Heterocycles as Ligands for Lanthanides Separation

Quantum chemical calculations combined with QSPR methodology reveal challenging perspectives for the solution of a number of fundamental and applied problems. In this work, we performed the PM7 and DFT calculations and QSPR modeling of HOMO and LUMO energies for polydentate N‐heterocyclic ligands promising for the extraction separation of lanthanides because these values are related to the ligands selectivity in the respect to the target cations. Data for QSPR modeling comprised the PM7 calculated HOMO and LUMO energies of N‐donor heterocycles, including several types of both known and virtual undescribed polydentate ligands. Ensemble modeling included various molecular fragments as descriptors and different variable selection techniques to build consensus models (CMs) on a training set of 388 ligands using external cross‐validation. CMs were then verified to make predictions for two external test sets: 45 ligands (T1) that were similar to the ligands of the training set, and 1546 structures (T2), which were substantially different from the ligands of the training set. The consensus models predict well in 5‐fold cross‐validation (RMSEHOMO=0.097 eV, RMSELUMO=0.064 eV), and on the external test sets (T1: RMSEHOMO=0.26 eV, RMSELUMO=0.24 eV; T2: RMSEHOMO=0.26 eV, RMSELUMO=0.17 eV). An analysis of the results reveals that substituents in heteroaromatic rings of the ligands and at the amide nitrogens can deeply influence their metal binding properties.

An unexpected product of the reactions of fluorenylchlorosilanes with phosphorus ylides

The reaction of Me3PCh2 with R1R2Si(C13H9) Cl(C13H9= fluoren-9-yl), irrespective of the molar ratio of reagents, yields betaines of the Me3P+CH2SiR2R2(C13H8–) type, whereas under similar conditions the reaction of bis(trimethylsilylmethyl)fluoren-9-ylchlorosilane with Ph3PCMe2 gives a stable organosilicon carbanion (X-ray analysis); the compounds were characterized by 13C, 29Si, and 31P n.m.r., and u.v. spectroscopy.