Detecting the Subtle Photo-Responsive Conformational Bistability of Monomeric Azobenzene Functionalized Keggin Polyoxometalates by Using Ion-Mobility Mass Spectrometry

Accurately characterizing the conformational variation of novel molecular assemblies is important but often ignored due to limited characterization methods. Herein, we reported the use of ion-mobility mass spectrometry (IMS/MS) to investigate the conformational changes of four azobenzene covalently functionalized Keggin hybrids (azo-Keggins, compounds 1–4). The as-prepared azo-Keggins showed the general molecular formula of [C₁₆H₃₆N]₄[SiW₁₁O₄₀(Si(CH₂)₃NH–CO(CH₂)_nO–C₆H₄N=NC₆H₄–R)₂] (R = H, n = 0 (1); R = NO₂, n = 0 (2); R = H, n = 5 (3); R = H, n = 10 (4)). The resultant azo-Keggins maintained stable monomeric states in the gas phase with intact molecular structures. Furthermore, the subtle photo-responsive trans-cis conformational variations of azo-Keggins were clearly revealed by the molecular shape-related collision cross-section value difference ranging from 2.44 Ų to 6.91 Ų. The longer the alkyl chains linkers were, the larger the conformational variation was. Moreover, for compounds 1 and 2, higher stability in trans-conformation can be observed, while for compounds 3 and 4, bistability can be achieved for both of them.     

New heteroorganic betaines containing the (+)E15—C—E14—X(–) and (+)E15—C—E14(–) structural fragments (E15 = P,As; E14 = Si,Ge, Sn; X = C,S, O,NR)

The review surveys the data on the reactions of phosphorus and arsenic ylides with compounds containing E=X bonds (E = C, Si, Ge, or Sn; X = C or S), cyclic oligomers (R₂ES)_n (n = 2 or 3), and heavier analogs of carbenes. These reactions give rise to two new classes of heteroorganic betaines containing the ⁽⁺⁾E¹⁵—C—E¹⁴—X^(–) (I) and ⁽⁺⁾E¹⁵—C—E^14(–) (II) (E¹⁵ = P or As; E¹⁴ = Si, Ge, or Sn; X = C or S) structural fragments. Procedures for the synthesis of these compounds, their reactivities, the X-ray diffraction structures, and the electronic structures established by high-level quantum-chemical calculations are considered in detail. The carbon analogs of betaines of type I, viz., compounds bearing the ⁽⁺⁾P—C—C—X^(–) fragment (III), are also discussed. The latter were long considered as possible intermediates in the reactions of compounds containing the polar C=X bond (X = C, O, S, NR, etc.) with phosphorus ylides (classical Wittig and Corey—Chaykovsky reactions and related processes).     

Reactions of organylhalosilanes with 1,1,3,3-tetra- and hexamethyldisilazane

Organylchlorosilanes, and also SiCl₄, decompose 1,1,3,3-tetra- and hexamethyl-disilazanes with formation of hitherto unknown organylchlorosilazanes of general formulas R_4–nSiCl_n–1NHSiH(CH₃)₂ and R_4–nSiCl_n–1NHSi(CH₃)₃ (n=2–4) in yields of 54–98%. The IR and mass spectra of the prepared compounds were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1159–1162, May, 1991.     

Co-hydrolysis products of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions: Part 2 [1]

²⁹Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O^–)_4/2 and CH₃Si(O^–)_3/2 units, (CH₃) _n Si₈O _{20 – n} ^{/(8 – n) –} (n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that ²⁹Si NMR peaks due to Si(OSi)₃(O^–) units shift to lower frequencies by replacement of the adjacent Si(O^–)_4/2 units by CH₃Si(O^–)_3/2 units, in other words, with increasing m value in Si[OSi(O^–)₃]_{3 – m} [OSi(CH₃) (O^–)₂] _m (O^–) (m=0–2). Peaks from CH₃ Si(OSi)₃ units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH₃Si(O^–)_3/2 units in the cubic octameric siloxane framework of (CH₃) _n Si₈O _{20 – n} ^{/(8 – n) –} (n=2, 3), for both of which three isomers are present, have been estimated.     

Chromato-mass spectral study of the reactions of organylsiloxanes with metal oxides

A study was carried out on the reaction of 1,1,3,3-tetramethyldisiloxane with metal oxides such as CuO, HgO, and Sb₂O₅ in the presence of compounds containing a siloxane bond such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, and trimethylacetoxysilane, which, at 100–110°C over 0.5–10 h, leads to the formation of linear organyl siloxanes (CH₃-[-Si(CH₃)₂O-]_n-Si(CH₃)₃, CH₃-[-Si(CH₃)₂O-]_n-Si (CH₃)₂H, and H-[-Si(CH₃)₂O-]_n-Si(CH₃)₂H, where n=2–6, and cyclic organylsiloxanes. The reaction does not proceed in the presence of aluminum, bismuth, germanium, and lead oxides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1658–1660, July, 1990.     

Synthesis,properties, and proton spectra of complex compounds AlHnCl3−n·N(C2H5)3

Conclusions Complexes with the composition AlH_nCl_3–nN(C₂H₅)₃ (n=0, 1, 2, 3) were produced. The IR and PMR spectra of the complexes indicate that when hydrogen atoms are replaced by chlorine atoms, an increase is observed in the acceptor capacity of aluminum compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2171–2173, October, 1974.     

Volumetric properties of tetraphenylporphine,their metallo-complexes and some substituted tetraphenylporphines in benzene solution

Densities, apparent molar volumes and partial molar volumes of benzene solutions of tetraphenylporphine, H₂TPP, tetraphenylporphine metallo-complexes, MTPP (where M=Ni,Cu,Zn,Pd,Ag, and Cd), and some substituted tetraphenylporphines H₂T(i-R)PP (where i=2–4 and R=–Cl,–CH₃,–OCH₃) H₂T(i-F)PP (where i-2,3), H₂T(3-Br)PP, and H₂T(3-I)PP were determined at 25°C. It was found that the partial molar volumes of the studied compounds correlate linearly with the first ionization potential of the corresponding metal atom. The calculated values of the surface and volume accessible to the solvent, and the solvent-excluded volume for different conformations of H₂TPP, were compared with experimental data. The volume per molecule for different crystalline forms of H₂TPP and MTPP were compared with the partial molar volumes of the corresponding compounds in benzene solutions. The correlation between the partial molar volumes of H₂T(3-R)PP and their Van der Waals volumes are presented for R=–H, –F,–CH₃,–Cl,–Br,–OCH₃, and –I. The experimental data are rationalized in terms of differences in the conformational states of the molecules.     

Study of the extraction of uranium (VI) by bis-(di-n-butylphosphate) compounds including a polyheteroatomic chain from nitrate solutions

Compounds 1–4 with two di-n-butylphosphate groups linked by a polyheteroatomic chain BuO)₂P(O)OCH₂(CH₂XCH₂)_nCH₂OP(O)(OBu)₂ (1: n = 0; 2: n = 1, X = 0; 3: n = 2, X = 0; 4: n = 1, X = S) were prepared respectively by action of chlorodi-n-butylphosphate on ethyleneglycol, di and triethyleneglycol, and thiodiethyleneglycol under phase transfer conditions.The extraction of uranium (VI) from aqueous nitrate phase with these compounds, in toluene diluent, was studied. Distribution ratios with compounds 1–3 are somewhat greater than those obtained with tri-n-butyl-phosphate. Extraction studies reveal that polyoxygenated chain of these compounds takes part in U(VI) complexation. The general expression for the complexes is assumed to be UO₂(NO₃)₂L_m in which L is extractant compound and m the number of molecules coordinated to uranyl cation. Extraction stoichiometry is dependent upon extractant compound and its concentration in organic phase. For the compounds 1–3, m = 1.5 when extractant concentration is higher than 0.1 M; m takes the different values 0.5, 1.0 and 1.5 when extractant concentration is lower than 0.1 M For the compound in which X is sulfur atom, m= 2.0 over all studied concentration range.It was found that in the solvent extraction of uranium (VI) with these compounds, di-n-butylphosphoric acid exhibits a synergistic effect increasing the distribution ratio of U(VI) by a factor of 100.     

Comparative study by single crystal X-ray structure determinations of tetramethylaminoborane and tetramethylethene at 110 K

The single crystal structures of the two isoelectronic and isosteric compounds tetramethylaminoborane and tetramethylethene have been determined by an X-ray study at 110 K. The distances of the central bonds are refined to 140.3(1) pm (B=N) and 134.8(1) pm (C=C), the CXXC-torsion angles (XX=CC, BN) are smaller than 1° in both compounds. A bond-length-bond-order correlation for the aminoboranes [(CH₃)₂N] _n B(CH₃)_3–n withn=1, 2, and 3 give a regression coefficient of 0.9977, the same is found for the CNC-angle as a function of the CBNC-torsion angle. Also, the comparison among these aminoboranes show that the variation of CBNC-torsion angles has more influence on bond lengths at small angles.     

Synthesis and some properties of furylacrylates of aluminium(III) and titanium(IV)

Summary Compounds of the type [M(OPrⁱ)_m–n(FA)_n] (where m = 3 and n = 1 to 3 when M = Al; and m = 4 and n = 1 to 4 when M = Ti) have been synthesised by the reactions of aluminium and titanium isopropoxides with furylacrylic acid (HFA) in benzene. The corresponding tertiary butoxide derivatives, [M(OBu^t)_m–n(FA)_n], were also obtained by the alcohol-interchange technique. These compounds have been characterised by elemental analysis, and i.r. and p.m.r. spectra.     

Co-hydrolysis products of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions

Tetracethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) have been co-hydrolyzed in methanolic solutions containing tetramethylammonium ions that only affect polymerization of silicate species (hydrolysis products of TEOS) to form the Si₈O ₂₀ ^8– cubic octameric silicate species. The effects of water content and TEOS-to-MTEOS molar ratio on the distribution of species formed in the solutions have been investigated with the trimethylsilylation technique and ²⁹Si n.m.r. spectroscopy. Formation of Si₈O ₂₀ ^8– and the cubic octameric species consisting of both Si(O^–)₄ and CH₃Si(O^–)₃ units, (CH₃)_nSi₈O _20–n ^(8–n)– (n=1–5), is found in the solutions. The increase of water content in the solutions solely results in increasing yield of Si₈O ₂₀ ^8– in spite of the presence of hydrolysis products of MTEOS together with those of TEOS, suggesting that water in the solutions plays an important role in the formation of Si₈O ₂₀ ^8– with the aid of tetramethylammonium ions. The TEOS-to-MTEOS molar ratio varies the distribution that is kept under control by the water content, increasing yields of (CH₃)_nSi₈O _20–n ^(8–n)– (n=1, 2). It is found that the water content and TEOS-to-MTEOS molar ratio determine the reaction conditions effective for the formation of CH₃Si(O^–)₃ unit-containing cubic octameric species.     

Low coordinate germanium and tin compounds (ArO)2ME and (ArO)2MM′Ln M=Ge, Sn; E=S, Se, –NSiMe3 M′=Cr, W, Fe, Pt [Ar=2,4,6-tris((dimethylamino)methyl)phenyl-]

The reactions of the divalent species (ArO)₂M (Ar=2,4,6-[(CH₃)₂NCH₂]₃C₆H₂; M=Ge, Sn) with either Me₃SiN₃, elemental S₈, Se or transition metal complexes M′(CO)_n+1 (M′=Fe, n=4; M′=Cr, W; n=5) (Ph₃P)₂Pt·C₂H₄ have resulted in the isolation of either the new stable formal metallanimines (ArO)₂M=N–SiMe₃, germanethione, -selone (ArO)₂Ge=E (E=S, Se) (the expected formations of the stannanethione and -selone were not observed), or the (ArO)₂M=M′(CO)_n, (ArO)₂M=Pt(PPh₃)₂ complexes, respectively. The direct oxidation of the (ArO)₂M species with various oxidizing agents led to the formation of the corresponding metalloxanes [(ArO)₂M–O–]₂. All of the chalcogenido- and transition metal–metal 14 complexes have been physicochemically and chemically characterized. The reactions of the (ArO)₂Ge=E (E=S, Se) compounds with 3,5-di-tert-butyl-1,2-benzoquinone produced, by extrusion of sulfur or selenium, the dioxametalloles corresponding to the formal addition of the divalent species (ArO)₂M to the benzoquinone. A substitution reaction of chalcogen (S/Se) has been observed permitting to go from germaneselone to germanethione.     

Characteristic Features of the Rhodium Stereochemistry in the Structure of Carbonyls and Organometallic Compounds

Characteristics of the Voronoi–Dirichlet polyhedra (VDP) were used to carry out crystal chemical analysis of 160 compounds containing 308 RhC _n or RhC _n Rh _m coordination polyhedra. The volume of the rhodium VDP virtually does not depend on the coordination number (C.N.), which varies from 4 to 12, in spite of the pronounced variation of the Rh–C (1.72–2.83 Å) and Rh–Rh (2.55–2.97 Å) bond lengths. It is shown that the VDP parameters allow one to estimate quantitatively the main features of rhodium stereochemistry irrespective of the nature (Rh or C) and the number (n varies from 3 to 12 and m varies from 0 to 6) of atoms in the first coordination sphere.     

Bromomethyl- and iodomethylacetoxysilanes

Conclusions The previously unknown bromomethyl- and iodomethylacetoxysilanes of general formula (CH₃)_3–nXCH₂-Si(OCOCH₃)_n (X = Br, I, n = 1-3) were synthesized by reacting the appropriate chloromethylacetoxysilanes with LiBr, NaBr, or NaI in refluxing anhydrous acetonitrile or acetone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 710–712,.March, 1978.     

Interaction of iron carbonyls with Lewis bases

The interaction of iron carbonyls Fe _n (CO) _m (wheren = 1,m = 5;n = 2,m = 9;n = 3,m = 12) with anionic Lewis bases (H^–, F^–, Cl^–, Br^– , I^–, CN^–, SCN^–, N₃ ^–, MeSO₃ ^–, MeCO₂ ^–, CF₃CO₂ ^–, S₂ ^–, CO₃ ^2–, and SO₄ ^2–) passes through two-stage redox-disproportionation. The first stage is the formation of an iron carbonyl-base complex, [Fe _n (CO) _m–1C(O)L]^–, and the second is a single-electron reduction of this complex by another molecule of the initial iron carbonyl, giving rise to Fe(l) and Fe(–l) derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 248–249, January, 1996.     

Lithiated γ-O-functionalized propyl phenyl sulfides and sulfones of the type Li[CH(SOxPh)CH2CH2OR] (x = 0, 2). [Li{CH(SPh)CH2CH2Ot-Bu}(tmeda)] – A structurally characterized organolithium inner complex

Lithiation of O-functionalized alkyl phenyl sulfides PhSCH₂CH₂CH₂OR (R = Me, 1a; i-Pr, 1b; t-Bu, 1c; CPh₃, 1d) with n-BuLi/tmeda in n-pentane resulted in the formation of α- and ortho-lithiated compounds [Li{CH(SPh)CH₂CH₂OR}(tmeda)] (α-2a–d) and [Li{o-C₆H₄SCH₂CH₂CH₂OR)(tmeda)] (o-2a–d), respectively, which has been proved by subsequent reaction with n-Bu₃SnCl yielding the requisite stannylated γ-OR-functionalized propyl phenyl sulfides n-Bu₃SnCH(SPh)CH₂CH₂OR (α-3a–d) and n-Bu₃Sn(o-C₆H₄SCH₂CH₂CH₂OR) (o-3a–d). The α/ortho ratios were found to be dependent on the sterical demand of the substituent R. Stannylated alkyl phenyl sulfides α-3a–c were found to react with n-BuLi/tmeda and n-BuLi yielding the pure α-lithiated compounds α-2a–c and [Li{CH(SPh)CH₂CH₂OR}] (α-4a–b), respectively, as white to yellowish powders. Single-crystal X-ray diffraction analysis of [Li{CH(SPh)CH₂CH₂Ot-Bu}(tmeda)] (α-2c) exhibited a distorted tetrahedral coordination of lithium having a chelating tmeda ligand and a C,O coordinated organyl ligand. Thus, α-2c is a typical organolithium inner complex.Lithiation of O-functionalized alkyl phenyl sulfones PhSO₂CH₂CH₂CH₂OR (R = Me, 5a; i-Pr, 5b; CPh₃, 5c) with n-BuLi resulted in the exclusive formation of the α-lithiated products Li[CH(SO₂Ph)CH₂CH₂OR] (6a–c) that were found to react with n-Bu₃SnCl yielding the requisite α-stannylated compounds n-Bu₃SnCH(SO₂Ph)CH₂CH₂OR (7a–c). The identities of all lithium and tin compounds have been unambiguously proved by NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn).     

Topological incremental scheme for calculating13C NMR chemical shifts in polysubstituted benzenes with substituents of one kind

A new topological approach to predicting the¹³C NMR chemical shifts of polysubstituted benzenes has been proposed (in the example case of compounds with substituents of one kind of the type C₆H_6–nX_n). The collective interactions of several substituents X [X=CH₃, C₂H₅, iso-C₃H₇, CF₃, COOH, f, Cl, Br, Si(CH₃)₃] have been expressed in the framework of a regression treatment in terms of two-particle increments. The chemical shift of each carbon atom has been represented in the form of an equation containing 17 parameters. The calculation scheme can be transformed and expanded for use even in the calculation of the spectra of compounds not previously studied. The calculated shifts for some previously investigated compounds and some compounds not previously investigated have been presented. The error in reproducing chemical shifts is equal to 0.2–0.3 ppm (and may be as high as 0.8 ppm for only a few measurements).V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 2, pp. 62–71, March–April, 1991.     

Solid-state chlorodecarboxylation of mono- and dicarboxylic acids with the Pb(OAc)<Subscript>4</Subscript>-MCl system

Solid state reactions of acids RCOOH (R = n-C₇H₁₅, BuC(Et)H, n-C₉H₁₉, PhCH₂, PhCH₂CH₂, H₂C=CH(CH₂)₈, or MeOOC(CH₂)₃) with Pb(OAc)₄ combined with KCl, NaCl, CdCl₂, or NH₄Cl in the absence of a solvent and without mechanical activation afford chlorohydrocarbons RCl. The corresponding reactions of acids HOOC(CH₂)_nCOOH (n = 3–6) give dichloroalkanes Cl(CH₂)_nCl and γ-butyrolactone (n = 3).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2105–2109, October, 2004.     

The Complexes of Holmium with Methylenediphosphonate and 1-Hydroxyethylidenephosphonate

The composition and stability of holmium methylenediphosphonate (MDP) and 1-hydroxyethylidenephosphonate (HEDP) complexes were studied by potentiometric titration methods in 0.1M NaCl at 25 °C. It was found that besides L^4– anions the protonated H _n L^(4–n)– species (n = 1–3 for MDP and n = 1–4 for HEDP) are present in the pH region 3 to 10. The presence of the undissociated acids (H₄L) has not been unambiguously proved for MDP. The complexes of the composition HoH _n L (n varies from 1 to –2 for MDP and from 1 to –1 for HEDP) have been found if the concentration of the ligand is higher than the concentration of holmium. The protonation constants of both acids and the stability constants of the complexes discussed were determined and the comparison with literature data of analogical complexes of other lanthanides was performed.     

2-(Trialkoxysilylalkylthio)ethyl vinyl sulfides

Conclusions Trialkoxysilylalkanethiols (CH₃O)₃Si(CH₂)_nSH (n=1–3) react with divinyl sulfide at 100–110° to give 2-(trialkoxysilylalkylthio)ethyl vinyl sulfides (CH₃O)₃Si(CH₂)_nS (CH₂)₂SCH=CH₂ in high yield. The reactivity of the trialkoxysilylalkanethiols decreases with increase in the number of CH₂ groups between the S and Si atoms. A second molecule of the organosilicon thiol acids adds with difficulty to divinyl sulfide to give the diadduct.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 197–199, January, 1977.