Tin(II) Halide Insertion or Halogen Exchange in the Reactions of Dihaloplatinum(II) Complexes with Tin(II) Halide

Reactions of SnCl₂ with the complexes cis‐[PtCl₂(P₂)] (P₂=dppf (1,1′‐bis(diphenylphosphino)ferrocene), dppp (1,3‐bis(diphenylphosphino)propane=1,1′‐(propane‐1,3‐diyl)bis[1,1‐diphenylphosphine]), dppb (1,4‐bis(diphenylphosphino)butane=1,1′‐(butane‐1,4‐diyl)bis[1,1‐diphenylphosphine]), and dpppe (1,5‐bis(diphenylphosphino)pentane=1,1′‐(pentane‐1,5‐diyl)bis[1,1‐diphenylphosphine])) resulted in the insertion of SnCl₂ into the Pt? Cl bond to afford the cis‐[PtCl(SnCl₃)(P₂)] complexes. However, the reaction of the complexes cis‐[PtCl₂(P₂)] (P₂=dppf, dppm (bis(diphenylphosphino)methane=1,1′‐methylenebis[1,1‐diphenylphosphine]), dppe (1,2‐bis(diphenylphosphino)ethane=1,1′‐(ethane‐1,2‐diyl)bis[1,1‐diphenylphosphine]), dppp, dppb, and dpppe; P=Ph₃P and (MeO)₃P) with SnX₂ (X=Br or I) resulted in the halogen exchange to yield the complexes [PtX₂(P₂)]. In contrast, treatment of cis‐[PtBr₂(dppm)] with SnBr₂ resulted in the insertion of SnBr₂ into the Pt? Br bond to form cis‐[Pt(SnBr₃)₂(dppm)], and this product was in equilibrium with the starting complex cis‐[PtBr₂(dppm)]. Moreover, the reaction of cis‐[PtCl₂(dppb)] with a mixture SnCl₂/SnI₂ in a 2 : 1 mol ratio resulted in the formation of cis‐[PtI₂(dppb)] as a consequence of the selective halogen‐exchange reaction. ³¹P‐NMR Data for all complexes are reported, and a correlation between the chemical shifts and the coupling constants was established for mono‐ and bis(trichlorostannyl)platinum complexes. The effect of the alkane chain length of the ligand and Sn^II halide is described.     

An Efficient One‐Pot,Four‐Component Synthesis of {[(1H‐1,2,3‐Triazol‐4‐yl)methoxy]phenyl}‐1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione Derivatives

The 1‐{[(1H‐1,2,3‐Triazol‐4‐yl)methoxy]phenyl}‐1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione derivatives 5 were synthesized by a simple and efficient method, i.e., by the four‐component, one‐pot condensation reaction of phthalohydrazide 4 , a (propargyloxy)benzaldehyde 1 , an active methylene compound 3 (malononitrile or ethyl cyanoacetate), and an azide 2 in the presence of Cu(OAc)₂/sodium L ‐ascorbate as catalyst and 1‐methyl‐1H‐imidazolium trifluoroacetate ([Hmim](CF₃COO)) as an ionic‐liquid medium in good to excellent yields (Scheme 1).     

Application of the UNIFAC model for prediction of surface tension and thickness of the surface layer in the binary mixtures

The specific sorption of Eu(III) and Y(III) on γ-alumina was investigated with solid-state (1)H NMR. Solution pH was shown to influence the recorded (1)H NMR spectra of γ-alumina, and thus, metal ion-containing samples were prepared under constant pH conditions, 8.00±0.05. The metal ion concentration in the samples was varied between 6.58×10(-7) M - 3.95×10(-4) M in case of Y(3+) and 6.58×10(-8) M - 1.32×10(-4) M in case of Eu(3+). The mineral concentration was kept constant at 4 g/l. After separation of the liquid phase, the samples were dried under vacuum to remove physisorbed water from the mineral surface. However, even after 48 h of drying at 150°C and 20 mTorr, water was still detected in the proton spectra as two distinct peaks with chemical shifts at 1.3 and 0.9 ppm. The europium addition to the γ-alumina samples induced significant spectral changes in comparison with yttrium-containing samples. These changes were attributed to the paramagnetism of europium rather than to complexation reactions occurring on the mineral surface. Proton spectra obtained for yttrium samples were therefore used to detect the spectral changes induced by the sorption reaction itself. The results revealed a large distribution of protons being removed from the mineral surface upon yttrium complexation. Removed protons were assigned to both bridging surface hydroxyls such as (Al(VI))(2)-OH as well as to terminal hydroxyls, e.g., of type Al(VI)-OH. Acidic protons belonging to (Al(VI))(3)-OH groups were not observed to participate in the surface reaction.     

A green and selective synthesis of 2‐aryloxazines and 2‐aryltetrahydropyrimidines

An efficient method for the selective synthesis of 2‐substituted oxazines and tetrahydropyrimidines by the reaction of arylnitriles with 3‐amino‐1‐propanol and 1,3‐diaminopropane in the presence of montmorillonite K‐10 and KSF as inexpensive, environmentally benign, and reusable catalysts under classical heating conditions and microwave irradiation is reported. J. Heterocyclic Chem., (2011).     

Stable silylenes with acyclic, cyclic, and unsaturated cyclic structures: Effects of heteroatoms and cyclopropyl α-substituents at DFT

The effects of alkyl, amino, phosphino, oxy, and thio moieties on the stability, multiplicity and reactivity of α-cyclopropylsilylenes with acyclic, cyclic, and unsaturated cyclic structures are compared and contrasted at B3LYP/AUG-cc-pVTZ//B3LYP/6-31G∗ level. The simultaneous stabilizing effects of heteroatom and cyclopropyl α-substituents on the above silylenes create the following trend of singlet-triplet energy gaps (?E_S-T): amino ≈ oxy > thio > alkyl > phosphino. The ΔE_S-T values for all the above silylenes increase through cyclization, because cyclization stabilizes singlet states of all our α-heteroatom substitued silylenes while destabilizes their corresponding triplet states. The ΔE_S-T values for all the heteroatom substituted cyclic silylenes decrease upon unsaturation, due to the higher stabilization of triplet compared to the singlet state. Interestingly, isodesmic reactions showed the phosphino substituents stabilize the triplet more than the corresponding singlet states, not only in the unsaturated form but also in the acyclic and cyclic structures. This is in contrast to cyclopropyl which stabilizes singlet considerably more than the corresponding triplet states. The reactivity of the above silylenes is discussed in terms of nucleophilicity, and electrophilicity; showing phosphino- and aminocyclopropylsilylenes more nucleophilic than oxy- and thiocyclopropylsilylenes.     

Molecular dynamics simulation of NMR powder lineshapes of linear guests in structure I clathrate hydrates

We perform molecular dynamics simulations (up to 6 ns) for the structure I clathrate hydrates of linear molecules CS, CS(2), OCS, and C(2)H(2) in large cages at different temperatures in the stability range to determine the angular distribution and dynamics of the guests in the large cages. The long axes of linear guest molecules in the oblate large structure I clathrate hydrate cages are primarily confined near the equatorial plane of the cage rather than axial regions. This non-uniform spatial distribution leads to well-known anisotropic lineshapes in the solid-state NMR spectra of the guest species. We use the dynamic distribution of guest orientations in the cages during the MD simulations at different temperatures to predict the (13)C NMR powder lineshapes of the guests in the large cages. The length of the guests and intermolecular interactions of the guests in the water cages determine the angular distribution and the mobility of the guests in the sI large cages at different temperatures. At low temperatures the range of motion of the guests in the cages are limited and this is reflected in the skew of the predicted (13)C lineshapes. As the guest molecules reach the fast motion limit at higher temperatures, the lineshapes for CS, OCS, and C(2)H(2) are predicted to have the "standard" powder lineshapes of guest molecules.     

Interaction of bare and gold-coated superparamagnetic iron oxide nanoparticles with fetal bovine serum

Superparamagnetic iron oxide nanoparticles (SPIONs) are being increasingly used in various biomedical processes such as hyperthermia, cell and protein separation, enhancing resolution of magnetic resonance imaging and drug delivery. Here, SPIONs were prepared by optimized co-precipitation of iron chlorides in basic medium and then coated with gold. Bare SPIONs and Aucoated SPIONs were characterized by TEM before incubation with fetal bovine serum for 0.5, 1, 2, 4, 8 and 24 h. After these interaction times, the mixture was deposed on a small column in a strong magnetic field (MACS?system). The SPIONs were retained; different washing fractions were collected and studied by UV-Vis spectroscopy and by 1D gel electrophoresis. The study revealed the presence of proteins in the washing solutions and confirmed the strong interaction of the protein with the SPIONs.     

Efficient synthesis of symmetrical and unsymmetrical acyclic imides catalyzed by reusable 12-tungstophosphoric acid under thermal conditions and microwave irradiation

An efficient and environmentally friendly procedure has been developed for the synthesis of symmetrical and unsymmetrical acyclic imides by the reaction of nitriles with acyclic anhydrides in the presence of catalytic amounts of 12-tungstophosphoric acid (H₃PW₁₂O₄₀) under thermal conditions and microwave irradiation. It was found that microwave improves the yields and significantly reduces the reaction times. Furthermore, the catalyst could be recovered and reused several times without decrease in its activity.     

Rapid and Efficient Synthesis of Imidazolines and Bisimidazolines Under Microwave and Ultrasonic Irradiation

Small assemblies of 2-imidazolines and bisimidazolines from appropriate nitriles and ethylenediamine with catalytic amounts of P₂S₅ employing a microwave assisted protocol were prepared. Sonication of this system also led to successful synthesis of 2-imidazolines and bisimidazolines. Another advantage of these systems is the ability to carry out large scale reactions.