Iridoid and acyclic monoterpene glycosides, kankanosides L, M, N, O, and P from Cistanche tubulosa

Three iridoid glycosides, kankanosides L, M, and N, and two acyclic monoterpene glycosides, kankanosides O and P, were isolated from fresh stems of Cistanche tubulosa (Orobanchaceae) together with eight iridoid glycosides, five acyclic monoterpene glycosides, three phenylpropanoid glycosides, and four lignan glycosides. Their structures were elucidated on the basis of chemical and physicochemical evidence.     

Theoretical study of isomerism in the molecules N2O,PNO, P2O,N2S,PNS, and P2S

We have carried out nonempirical calculations of the potential surface for isomeric rearrangements of the molecules N₂O, N₂S, PNO, PNS, P₂O, and P₂S. It was found that for the molecules N₂O and N₂S a linear structure is considerably more favorable than a cyclic one, which lies 60 kcal·mole^–1 higher and has low stability. For P₂O and P₂S the linear and cyclic isomers have similar energies. For PNO and PNS there are two linear isomers and one cyclic isomer. The isomers are separated by appreciable barriers and can exist independently. It is predicted for the ABC molecules with 16 valence electrons that if two or all three of the atoms belong to the third or a later period, then the cyclic isomers should be favored to at least the same extent as the linear isomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 794–802, April, 1990.     

On the existence of several New O,N,F-Compounds. A Critical Comment on the paper by SICRE and SCHUMACHER

It is shown that the infrared spectra previously attributed to the three novel compounds FONO, NO₂F₃, and an unknown are due to the known compounds HONO₂, FONO₂, and covalent N₂O₅, respectively. The observed chemical and physical properties agree well with this reinterpretation.     

A study of the reaction NO3 + NO2 + M → N2O5 + M(M = N2, O2)

The gas-phase reaction of the NO₃ radical with NO₂ was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10^?13 cm³ molecule^?1 s^?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N₂ and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O₂. These data show that the third-body efficiencies of N₂ and O₂ are identical, within the error limits, and that previous evaluations for M = N₂ are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO₃ radical with methanol, ethanol, and propan-2-ol of ?6 × 10^?16, ?9 × 10^?16, and ?2.3 × 10^?15 cm³ molecule^?1 s^?1, respectively, at 298 ± 2 K.     

Quenching of I(2P1/2) by NO2, N2O4, and N2O

Quenching of excited iodine atoms (I(5p5, 2P1/2)) by nitrogen oxides are processes of relevance to discharge-driven oxygen iodine lasers. Rate constants at ambient and elevated temperatures (293-380 K) for quenching of I(2P1/2) atoms by NO2, N2O4, and N2O have been measured using time-resolved I(2P1/2) --> I(2P3/2) 1315 nm emission. The excited atoms were generated by pulsed laser photodissociation of CF3I at 248 nm. The rate constants for I(2P1/2) quenching by NO2 and N2O were found to be independent of temperature over the range examined with average values of (2.9 +/- 0.3) x 10(-15) and (1.4 +/- 0.1) x 10(-15) cm3 s(-1), respectively. The rate constant for quenching of I(2P1/2) by N2O4 was found to be (3.5 +/- 0.5) x 10(-13) cm3 s(-1) at ambient temperature.     

A Stable Seven‐Membered Heterocycle,Containing B,C, N,O, and P Atoms,inside a Smaragdyrin Macrocycle

Unprecedented examples of smaragdyrin macrocycles containing seven membered heterocyclic rings were synthesized under simple reaction conditions in high yields. The heterocycle formed inside smaragdyrin macrocycle is rare example of heterocycle containing five different atoms, such as B, C, N, O, and P atoms. The mixed B^III and P^V complexes of smaragdyrin macrocycles showed new structural, spectral, and electrochemical properties.     

Convenient and improved protocols for the hydrogenation of esters using Ru catalysts derived from (P,P), (P,N,N) and (P,N,O) ligands

An improved protocol where a pre-cursor, [Ru(Cl)(2)(NBD)(Py)(2)], is treated with ligands to form [RuCl(2)(bidentate ligand)(diamine)] pre-catalysts for ester hydrogenation is reported. This family of catalysts, as well as a range of ruthenium complexes of tridentate P^N^X (X = NR(2), OH) ligands have been investigated in the hydrogenation of aromatic esters. A range of aromatic esters can be hydrogenated in high yields at temperatures between 30 °C and 100 °C.     

Re tricarbonyl complexes with ligands containing P,N,N and P,N,O donor atom sets: synthesis and structural characterization

The coordination chemistry of the heterofunctionalized phosphines HPN2 and H2PNO and of an analogue containing a relevant biomolecule, HPN-Pip (Pip = 4-(3-aminopropyl)-1-(2-methoxyphenyl)piperazine), was studied toward the synthon (NE4)2[ReBr3(CO)3]. The complexes isolated, [Re(CO)3(kappa(3)-PN2)], 3, [Re(CO)3Br(kappa(2)-H2PNO)], 4, and [Re(CO)3Br(kappa(2)-HPN-Pip)], 5, are the first examples of Re(I) compounds stabilized by such a combination of donor atoms. All of the compounds are neutral, but the phosphines, depending on the combination of atoms, act as monoanionic and tridentate (3) or as neutral and bidentate (4, 5). The characterization of 3-5 included IR, 1H NMR, and 31P NMR spectroscopy and X-ray crystallographic analysis. Colorless crystals of compounds 3 and 4 were obtained by slow evaporation of a methanolic solution of 3 and from a boiling acetonitrile solution of 4. Compound 3 crystallizes with two molecules of MeOH per asymmetric unit in the monoclinic space group P2(1)/c, a = 10.1237(8) A, b = 9.4959(4) A, c = 28.365(2) A, beta = 98.707(9) degrees, V = 2695.4(3) A(3), Z = 4; 4 crystallizes in the triclinic space group Ponebar, a = 10.0241(9) A, b = 11.2060(10) A, c = 13.0656(12) A, alpha = 84.883(11) degrees, beta = 71.163(10) degrees, gamma = 63.650(9) degrees, V = 1241.19(19) A(3), Z = 2.     

A reinvestigation of the temperature dependence of the rate constant for the reaction O + O2 + M → O3 + M (for M = O2, N2, and Ar) by the flash photolysis resonance fluorescence technique

The flash photolysis resonance fluorescence technique has been used to reinvestigate the kinetics of the oxygen atom–oxygen molecule combination reaction. Third-order rate constants for O₂, N₂, and Ar as deactivant molecules were determined over the temperature range of 219–368 K. The results presented herein are the most extensive data sets available for atmospheric modeling and are used to formulate a recommendation for such purposes. The recommended rate expressions are or Comparisons of these results with existing literature data are presented.     

Variable coordination behaviour of pyrazole-containing N,P and N,P(O) ligands towards palladium(II)

Three bidentate, mixed-donor ligands based on a triphenylphosphine unit bearing a pyrazole group in the ortho-position of one phenyl ring have been synthesised; the N,P ligand [2-(3-pyrazolyl)phenyl]diphenylphosphine pzphos has been synthesised and transformed into new N,P(O) and N,P(S) derivatives, [2-(3-pyrazolyl)phenyl]diphenylphosphine oxide pzphos(O) and [2-(3-pyrazolyl)phenyl]diphenylphosphine sulfide pzphos(S), respectively. The coordination chemistry of pzphos and pzphos(O) towards palladium(II) has been investigated. Depending on the ligand to metal molar ratio employed in the reactions of palladium(II) with pzphos, either the 1 : 1 chelate [Pd(pzphos)Cl2] 1a or the 2 : 1 N,P chelate [Pd(pzphos)2]Cl2 1b was obtained. 1b contains two six-membered chelate rings in which the chlorides have been displaced from the inner coordination sphere of palladium. Exchange of the chloride anions in 1b for perchlorate anions was achieved using AgClO4 to give [Pd(pzphos)2][ClO4]2 1c. Reaction of pzphos(O) under the same conditions forms the 2 : 1 adduct [Pd(pzphos(O))2Cl2] 2b regardless of the metal to ligand ratio or the order of addition of reactants. Unlike the N,P chelate 1b, the N,P(O) ligands in complex 2b bind in a monodentate fashion through the N-donor atoms of the pyrazole rings. Abstraction of the chloro ligands in compound 2b using AgClO4 gave the 2 : 1 N,P(O) chelate [Pd{pzphos(O)}2][ClO4]2 2c, in which entropically unfavourable 7-membered chelate rings are formed. X-Ray diffraction has been used to confirm the solid-state structures of the pzphos(O) ligand and the complexes 1b, 1c, 2b and 2c.     

On the Reactivity of P Trichloro N Dichlorophosphor-Yl-Mdnophosphazene Cl3P=N-P(O)Cl2

Abstract

In this poster we give the results of some reactions of P trichloro N dichlorophosphoryl monophosphazene Cl₃P=N-P(O)Cl₂ (I) with inorganic and organic nucleophilic reagents.     

Stability of nitrogen-oxygen cages N12O2, N14O2, N14O3, and N16O4

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high energy density materials (HEDM). However, many such molecules are too unstable to serve as practical energy sources. This has prompted many studies of molecules that are mostly nitrogen but which incorporate heteroatoms into the structure to provide additional stability. In the current study, cages of three-coordinate nitrogen are viewed as candidates for stabilization by insertion of oxygen atoms into the nitrogen framework. Cages of N12, N14, and N16 with four-membered rings are studied because four-membered rings have been previously shown to be a destabilizing influence. Insertion of oxygen atoms, which converts N-N bonds to N-O-N bonding groups, relieves ring strain and can potentially result in stable molecules. These molecules are studied by theoretical calculations, using Hartree-Fock and Moller-Plesset (MP3 and MP4) theories, to determine the dissociation energies of the molecules. The primary result of the study is that stable molecules can result from oxygen insertion but that oxygen-oxygen proximity destabilizes the insertion products.     

31P N.M.R. studies of some pseudo-halogeno-derivatives of phosphorus

Abstract

Several new pseudo-halogeno phosphorus species, including isomeric N- and O-bonded cyanato-derivatives of the PCl₆ ^? ion, cyano-derivatives of RPCl₅ ^? ions (R [dbnd] Ph or Me), and organo-phosphorus (III) cyanide adducts RP(CN)₂X^? (R [dbnd] Me, Et, Ph or C₆F₅; X [dbnd] Cl, Br or I) have been prepared in solution, and identified by means of ³¹P n.m.r. spectroscopy. Isomeric configurations in the six-coordinate species have been assigned by the method of pairwise interactions.