A Selective Conversion of Benzylic Alcohols to the Corresponding Carbonyl Compounds by Means of an Ag(III) Complex

Summary.  Carbonyl compounds of the type XPhCOR (R = H, Me, Ph; X = H, Me, Cl, Br) are prepared in high yields by reaction of the corresponding benzylic alcohols XPhCHOHR with KNa₄ [Ag(HIO₆)₂]×12H₂O in alkaline solution. This method allows the selective oxidation of benzylic alcohols in compounds containing other types of alcoholic functional groups. Received January 18, 2000. Accepted (revised) February 23, 2000     

Synthesis and Reactivity of Stannyloligosilanes IV [1]: From Hydrido Substituted Stannasilanes Towards Stannasiloxanes

Summary.  Hydrido substituted stannasilanes of the type or (Z = H, Me, Ph; R, R′ = alkyl, Ph) are accessible by reaction of either alkali metal stannides (MSn(Z)R ₂; M = Li, Na) with halogen substituted silanes (; X = F, Cl) or chlorostannanes (R ₂SnCl₂, Ph₃SnCl) and fluorosilanes in the presence of magnesium. Stannasilanes with halogen substituents at the silicon as well as the tin atom are formed by treatment of the hydrido substituted stannasilanes with CHCl₃ or CCl₄. The hydrido substituted stannasilanes decompose in contact with air to distannanes and siloxanes or to the linear ( ^t Bu₂Sn(–O– ^t Bu₂Si–OH)₂) and cyclic ((– ^t Bu₂Sn–O– ⁱ Pr₂Si–O–)₂) stannasiloxanes. Received November 29, 2001. Accepted (revised) January 16, 2002     

PCC-mediated novel oxidation reactions of homobenzylic and homoallylic alcohols

A new PCC-mediated carboncarbon bond cleavage reaction during oxidation of homobenzylic alcohols leading to the formation of benzylic carbonyl compounds has been observed. Homobenzylic alcohols with no benzylic substitution (R¹=H) gave benzylic aldehydes without further oxidation, while those with benzylic substitution (R¹=Me, Et, Ar) gave benzylic ketones. In contrast, homoallylic alcohols gave products arising from double bond migration, cis- to trans-olefin isomerization and/or allylic oxidation.     

Excitonic Bands in the Spectra of Some Organic-Inorganic Hybrid Compounds Based on Metal Halide Units

Summary.  The optical absorption, photoluminescence, and photoconductivity spectra of some compounds of the formulas [R(CH₂) _n NH₃] _x M _y X _z , [R(CH₂) _n NH(CH₃)₂] _x M _y X _z , [R(CH₂) _n S(CH₃)₂] _x M _y X _z , [R(CH₂) _n SC(NH₂)₂] _x M _y X _z , and [R(CH₂) _n SeC(NH₂)₂] _x M _y X _z (R = organic residue; M = Bi(III), Pb(II), Sn(II), Cu(I), Ag(I) etc; X = I, Br, Cl; n, x, y, z = 0, 1, 2, 3, …) are briefly reviewed, and some new results are reported. The position, intensity, and shape of the excitonic bands depend on the dimensionality and size of the inorganic network as well as on the nature of the M, X, R, and onium moieties. Received June 23, 2000. Accepted August 1, 2000     

Excitonic Bands in the Spectra of Some Organic-Inorganic Hybrid Compounds Based on Metal Halide Units

 The optical absorption, photoluminescence, and photoconductivity spectra of some compounds of the formulas [R(CH₂) _n NH₃] _x M _y X _z , [R(CH₂) _n NH(CH₃)₂] _x M _y X _z , [R(CH₂) _n S(CH₃)₂] _x M _y X _z , [R(CH₂) _n SC(NH₂)₂] _x M _y X _z , and [R(CH₂) _n SeC(NH₂)₂] _x M _y X _z (R = organic residue; M = Bi(III), Pb(II), Sn(II), Cu(I), Ag(I) etc; X = I, Br, Cl; n, x, y, z = 0, 1, 2, 3, …) are briefly reviewed, and some new results are reported. The position, intensity, and shape of the excitonic bands depend on the dimensionality and size of the inorganic network as well as on the nature of the M, X, R, and onium moieties.     

The synthesis and characterisation of novel dimethyl- and diphenyl-silanediolates

Dimethyl- and diphenylsilanediolates are key intermediates in the preparation of dimethyl- and diphenyl-siloxane polymers. Both dimethyl- and diphenylsilanediolates R₂Si(OM)₂, where R = Me or Ph, and M = Li, Na and K were synthesised by the reaction between dimethyl- and diphenylsilanediol and a metal or metal hydride (M/MH where M = Li, Na and K). The silanediolates were characterised by ²⁹Si, ¹³C and ¹H NMR, FTIR and mass spectroscopy.     

Polymorphism and Pressure Driven Thermal Spin Crossover Phenomenon in [Fe( abpt )2(NC X )2] ( X =?S, and Se): Synthesis, Structure and Magnetic Properties

Summary.  The monomeric compounds [Fe(abpt)₂(NCX)₂] (X = S (1), Se (2) and abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) have been synthesized and characterized. They crystallize in the monoclinic P2₁/n space group with a = 11.637(2) ?, b = 9.8021(14) ?, c = 12.9838(12) ?, β = 101.126(14)°, and Z = 2 for 1, and a = 11.601(2) ?, b = 9.6666(14) ?, c = 12.883(2) ?, β = 101.449(10)°, and Z = 2 for 2. The unit cell contains a pair mononuclear [Fe(abpt)₂(NCX)₂] units related by a center of symmetry. Each iron atom, located at a molecular inversion center, is in a distorted octahedral environment. Four of the six nitrogen atoms coordinated to the Fe(II) ion belong to the pyridine-N(1) and triazole-N(2) rings of two abpt ligands. The remaining trans positions are occupied by two nitrogen atoms, N(3), belonging to the two pseudo-halide ligands. The magnetic susceptibility measurements at ambient pressure have revealed that they are in the high-spin range in the 2 K–300 K temperature range. The pressure study has revealed that compound 1 remains in high-spin as pressure is increased up to 4.4 kbar, where an incomplete thermal spin crossover appears at around T _1/2 = 65 K. Quenching experiments at 4.4 kbar have shown that the incomplete character of the conversion is a consequence of slow kinetics. Relatively sharp spin transition takes place at T _1/2 = 106, 152 and 179 K, as pressure attains 5.6, 8.6 and 10.5 kbar, respectively. Corresponding author. E-mail: jose.a.real@uv.es Received June 12, 2002; accepted July 1, 2002     

Ca2+- and Mg2+-induced molecular interactions in a dehydrocholic acid/didodecyldimethylammonium bromide mixed monolayer

The aim of this article is the evaluation of Ca²⁺ and Mg²⁺ subphases presence effect on mixed monolayers composed by dehydrocholic acid (HDHC) and didodecyldimethylammonium bromide (DDAB). The monolayer stability was analyzed by the evaluation of thermodynamic parameters, ΔG _mix^E and α. At all calcium ion-tested concentration, the mixed systems X _HDHC = 0.6 and 0.8 at π = 30 mJ m⁻² were always the most favored proportions. The X _HDHC = 0.6 system was also stable in magnesium presence, and the X _HDHC = 0.2-mixed monolayer went through a stable to an unstable state as the content of Ca²⁺ or Mg²⁺ augment. Finally, the X _HDHC = 0.4 monolayer showed a particular behavior, i.e., remained stable at low cation concentration, unstable at intermediate concentration and stable again at high concentration. The effect was similar at Mg²⁺ presence.     

Separation of racemiccloso-3,3-(η3,2-norbornadienyl)rhodacarboranes into enantiomers by HPLC on chiral stationary phasesinto enantiomers by HPLC on chiral stationary phases

Racemiccloso-rhodacarboranes,vis. closo-(η^3,2-C₇H₃-2-CR ₂ ¹ )-1-R²-2-R³-3,1,2-RhC₂B₉H₉ (R¹=R²=R³=H; R¹=H, R²=R³=Me; R¹=R²=R³=Me) and (closo-2,2-(η^3,2-C₇H₇-2-CH₂)-2,1,7-RhC₂B₉H₁₁), were successfully separated into enantiomers by high-performance liquid chromatography (HPLC). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 759–761, April, 2000.     

Crystal Structures of Na3PO2S2 · 11H2O and Na3POS3 · 11H2O

Summary.  Single crystals of sodium dithiophosphate undecahydrate (Na₃PO₂S₂ · 11H₂O) and sodium trithiophosphate undecahydrate (Na₃POS₃ · 11H₂O) were grown from aqueous solution. The crystal structures of Na₃PO₂S₂ · 11H₂O (P2₁2₁2₁; a = 1248.1(1), b = 945.2(1), c = 1383.1(1) pm; R ₁ = 0.0202, wR ₂ = 0.0502) and Na₃POS₃ · 11H₂O (Pna2₁; a = 1262.0(2), b = 947.6(2), c = 1431.5(2) pm; R ₁ = 0.0720, wR ₂ = 0.1371) are related to each other in a sense that all constituting units are arranged in similar positions and with similar orientations. The geometries of the anions were determined with high accuracy; thus, the structural parameters of the POS³⁻ ₃ anion were measured for the first time. Received September 25, 2001. Accepted January 21, 2002     

Organotins as a Locking Agent in the Formation of Dinuclear Complexes

In this paper the synthesis and characterization of new heterobimetallic compounds with a ligand derived from diacetylpyridine, hydrazine and salicylaldehyde has been reported. The open end of the ligand was locked with R₂SnCl₂ followed by the insertion of a transition metal ion in the cavity thus formed by locking the ligand. These compounds are characterized by TGA/DSC, IR, ¹H and ¹³CNMR, electronic spectra, magnetic moment and conductivity measurements. The disappearance of ν(O–H) and appearance of ν(Sn–O) in the IR spectrum of the Sn(saldp)R₂ {where saldp = bis(salicylaldehydehydrazone)diacetylpyridine and R = –CH₃, –C₄H₉} suggests the complex formation with R₂SnCl₂. The IR spectra of the complexes exhibited a blue shift in ν(C=N) indicating coordination of the azomethine nitrogen. The complexes are non-electrolytes in DMSO. The ¹HNMR and ¹³CNMR spectra of the complexes are not much different from that of the free ligand except for the disappearance of the signal at 9 ppm due to phenolic protons. The methyl or butyl protons attached to the tin appear at their usual places. The TGA profile of the ligand and its mononuclear complexes exhibit a three-step pyrolysis, although the binuclear complexes decompose in two steps leaving behind tin oxide as the final product.     

Enantiomerically Pure Cyclic trans-1,2-Diols,Diamines, and Amino Alcohols by Intramolecular Pinacol Coupling of Planar Chiral Mono-Cr(CO)3 Complexes of Biaryls

Without any formation of stereoisomers , the intramolecular pinacol cyclization of 1 —planar chiral mono-Cr(CO)₃ complexes of 1,1′-biphenyls with carbonyl functionalities at the 2- and 2′-positions—with samarium diiodide gives cyclic trans-1,2-diols 2 . Upon exposure to sunlight, the chromium-complexed diols 2 produce optically pure chromium-free trans-diols 3 . Similarly, the corresponding enantiomerically pure trans-1,2-diamines and amino alcohols are obtained from the planar chiral chromium complexes of biphenyls with diimino or keto-imino functionalities. R¹=H, OMe; R²=H, Me; R³=H, Me.     

A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe

In this paper, a rapid, simple, and sensitive method was described for detection of the total bacterial count using SiO₂-coated CdSe/ZnS quantum dots (QDs) as a fluorescence marker that covalently coupled with bacteria using glutaraldehyde as the crosslinker. Highly luminescent CdSe/ZnS were prepared by applying cadmium oxide and zinc stearate as precursors instead of pyrophoric organometallic precursors. A reverse-microemulsion technique was used to synthesize CdSe/ZnS/SiO₂ composite nanoparticles with a SiO₂ surface coating. Our results showed that CdSe/ZnS/SiO₂ composite nanoparticles prepared with this method possessed highly luminescent, biologically functional, and monodispersive characteristics, and could successfully be covalently conjugated with the bacteria. As a demonstration, it was found that the method had higher sensitivity and could count bacteria in 3 × 10² CFU/mL, lower than the conventional plate counting and organic dye-based method. A linear relationship of the fluorescence peak intensity (Y) and the total bacterial count (X) was established in the range of 3 × 10²–10⁷ CFU/mL using the equation Y = 374.82X − 938.27 (R = 0.99574). The results of the determination for the total count of bacteria in seven real samples were identical with the conventional plate count method, and the standard deviation was satisfactory.     

Reactivity of C<Subscript>3</Subscript>-C<Subscript>8</Subscript> alkanes with nitronium ions in sulfuric acid

We have determined the parameters of the Arrhenius equation (E, log A) for reactions between \textNO₂⁺ {\text{NO}}_2^{+} ions and C₃-C₈ alkanes in HNO₃–93 wt.% H₂SO₄ solutions at 277–353 K, and we have also estimated the activation parameters E _j , log A _j for secondary and tertiary C—H bonds of these alkanes. We show that the following compensation relations are satisfied: E = 2.3R βlog A + C with isokinetic temperature β = 360 ± 65 K, and also E _j =2.3Rβ _j log A _j  + C _j , for secondary C—H bonds, β₂ =300 ± 60, and for tertiary C—H bonds, β₃ =310 ± 50.     

Analysis of the Solid-State Rearrangementof Hydrido-Alkynyl Ruthenium Complexesto their Vinylidene Tautomers

Summary.  The solid-state tautomerization of the hydrido-alkynyl derivatives [Cp ^*RuH(C&*CR)-(dippe)][BPh₄] (Cp^* = C₅Me₅; R = SiMe₃, Ph, H; dippe = 1,2-bis-(diisopropylphosphino)-ethane) to their vinylidene isomers [Cp ^*Ru*C*CHR(dippe)][BPh₄] was studied by IR spectroscopy. Characteristic isothermic αvs. t curves for each individual rearrangement process were recorded. Their shape, and hence the isomerization mechanism, depends strongly on the nature of the substituent R. The kinetic analysis of the above curves using the Avrami-Erofeev provided some mechanistic information about the isomerization process in the solid. Received July 7, 2000. Accepted August 29, 2000     

Synthesis and characterization of novel intramolecularly O,C,O-coordinated heteroleptic organostannylenes and their tungstenpentacarbonyl complexes

The syntheses are reported of the novel heteroleptic organostannylenes [2,6-(ROCH₂)₂C₆H₃]SnCl (1, R = Me; 2, R = t-Bu) and of their tungstenpentacarbonyl complexes [2,6-(ROCH₂)₂C₆H₃](X)SnW(CO)₅ (3, X = Cl, R = Me; 4, X = Cl, R = t-Bu; 5, X = H, R = Me). The compounds were characterized by means of elemental analyses, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopies, electrospray mass spectrometry and in case of 3 and 4 also by single crystal X-ray diffraction analysis. For the two latter compounds the substituents bound at the ether oxygen atom control the strength of intramolecular O → Sn coordination. Thus, the O–Sn distances amount to 2.391(5)/2.389(5) (3) and 2.464(3)/2.513(3) Å (4).     

Solvothermal Syntheses,Crystal Structures,and Properties of New [Mn(<Emphasis Type="BoldItalic">dien</Emphasis>)<Subscript>2</Subscript>]<Superscript>2+</Superscript> Complexes

Summary.  The two new compounds Mn(dien)₂[MoS₄] (1) and Mn(dien)₂[Mo₂O₂S₆] (2) (dien = diethylenetriamine) were prepared under solvothermal conditions. Both compounds were obtained as phase-pure products. The structures consist of new [Mn(dien)₂]²⁺ cations and isolated tetrahedral [MoS₄]²⁻ (1) or [Mo₂O₂S₆]²⁻ (2) anions. Between the anions and the cations, hydrogen bonding is observed. Compound 1 crystallizes in the tetragonal space group I (a = 10.219(2), c = 9.259(2) ?, Z = 2), whereas 2 crystallizes in the monoclinic space group P2₁/c (a = 8.703(2), b = 18.390(4), c = 14.603(3) ?, β = 103.18(3)°, Z = 4). The thermal behaviour of the thiomolybdates was investigated using difference thermoanalysis (DTA) and thermogravimetry (TG). Both compounds decompose under argon with a single endothermic signal in the DTA curve (peak maximum: 252 (1) and 242°C (2)). Received November 5, 2001. Accepted December 27, 2001     

Solvothermal Syntheses, Crystal Structures, and Properties of New [Mn( dien )2]2+ Complexes

 The two new compounds Mn(dien)₂[MoS₄] (1) and Mn(dien)₂[Mo₂O₂S₆] (2) (dien = diethylenetriamine) were prepared under solvothermal conditions. Both compounds were obtained as phase-pure products. The structures consist of new [Mn(dien)₂]²⁺ cations and isolated tetrahedral [MoS₄]²⁻ (1) or [Mo₂O₂S₆]²⁻ (2) anions. Between the anions and the cations, hydrogen bonding is observed. Compound 1 crystallizes in the tetragonal space group I (a = 10.219(2), c = 9.259(2) ?, Z = 2), whereas 2 crystallizes in the monoclinic space group P2₁/c (a = 8.703(2), b = 18.390(4), c = 14.603(3) ?, β = 103.18(3)°, Z = 4). The thermal behaviour of the thiomolybdates was investigated using difference thermoanalysis (DTA) and thermogravimetry (TG). Both compounds decompose under argon with a single endothermic signal in the DTA curve (peak maximum: 252 (1) and 242°C (2)).     

Electron density distributions in substituted 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes studied by NMR spectroscopy

The signals in the¹³C NMR spectra of 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes (R¹=R²=H, Me,cyclo-C₃H₅, SiMe₃, SnMe₃, R¹=Me, R²=H, Cl) were completely assigned using 2D NMR spectroscopy. The pattern of the variation of the chemical shifts in the¹³C NMR spectra indicates that the effects of substituents R¹ and R² on the heterocycle and on the phenyl groups are of inductive rather than mesomeric origin and include the direct through-space polarization of bonds (field effect). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1962–1965, November, 1997.     

Structural, Spectroscopic, and Thermal Behaviour of Bis -(thiosaccharinate)-aqua-cadmium(II)

 The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis.