Solution and mechanochemical syntheses, and spectroscopic and structural studies in the silver(I) (bi-)carbonate: triphenylphosphine system

Syntheses of a number of adducts of silver(I) (bi-)carbonate with triphenylphosphine, both mechanochemically, and from solution, are described, together with their infra-red spectra, (31)P CP MAS NMR and crystal structures. Ag(HCO(3)):PPh(3) (1:4) has been isolated in the ionic form [Ag(PPh(3))(4)](HCO(3))·2EtOH·3H(2)O. Ag(2)CO(3):PPh(3) (1:4) forms a binuclear neutral molecule [(Ph(3)P)(2)Ag(O,μ-O'·CO)Ag(PPh(3))(2)](·2H(2)O), while Ag(HCO(3)):PPh(3) (1:2) has been isolated in both mononuclear and binuclear forms: [(Ph(3)P)(2)Ag(O(2)COH)] and [(Ph(3)P)(2)Ag(μ-O·CO·OH)(2)Ag(PPh(3))(2)] (both unsolvated). A more convenient method for the preparation of the previously reported copper(I) complex [(Ph(3)P)(2)Cu(HCO(3))] is also reported.     

The formation and structural chemistry of the hexa(μ-t-butylthiolato) pentacuprate(I) cage anion with triethylammonium and tetraethylammonium cations

Yellow (Et₄N)[Cu₅(SBu^t)₆] crystallises from solutions prepared from Cu(II), Bu^tSH, Et₃N and Et₄NBr in acetone/ethanol, while (Et₃NH)[Cu₅(SBu^t)₆] crystallises from solutions of CuSBu^t and Bu^tSH in Et₃N. Crystal structure determinations reveal that both compounds contain the molecular cage [Cu₅(μ-SBu^t)₆]^?, in which two copper atoms are three-coordinate (Cu_trig), three copper atoms are two-coordinate (Cu_dig), and all thiolate ligands are doubly-bridging. The polyhedral stereochemistry of the core is trigonalbipyramido-Cu₅-trigonal antiprismo-S₆. The complete [Cu₅(μ-SBu^t)₆]^? cage in the Et₄N⁺ compound closely approaches D₃ symmetry, but in the Et₃NH⁺ compound one SBu^t ligand is inverted at the sulphur bridge, causing angular distortions in the cage.Two structural features, the antiprismatic twist of the S₆ polyhedron and the bending of Cu_dig towards the cage centroid (S-Cu_dig-S = 171(1)°), provide evidence for weak Cu-Cu attractive interactions within the cage. Infrared data are discussed. Crystal data: (Et₄N)[Cu₅(SBu^t)₆], C₃₂H₇₄Cu₅NS₆, a = 45.500 (3), b = 11.805(1), c = 20.168(2) Å, β = 117.81 (1)°, C2/c, Z = 8, R = 0.078 (2953 observed F); (Et₃NH)[Cu₅(SBu^t)₆], C₃₀H₇₀Cu₅NS₆, a = 10.519(1), b = 21.457(1), c = 20.065(1), β = 95.11(1), P2₁/c, Z = 4, R = 0.072 (3093 observed F). (Et₄N)[Ag₅(SBu^t)₆] is isostructural with (Et₄N)[Cu₅(SBu^t)₆].     

Temperature and solvent variation of the 13C and 1H NMR spectra of r-1,t-2,c-3,t-4-tetrachlorotetralin

Vicinal coupling constants in the ¹H and ¹³C NMR spectra of r-1,t-2,c-3,t-4-tetrachlorotetralin change with temperature and solvent in a manner better explained by conformational equilibration than by intramolecular or solvent-determined distortions.     

The parathiocyanogen electrode

Stable, yellow anodic films of parathiocyanogen (SCN) _x were formed on a platinum electrode from 2.8 M KSCN in methanol at 45 °C at a constant current of 20–40 mA cm⁻² for 15–30 min. Loosely bound orange crystals of a more amorphous character were removed by rinsing to leave an adherent yellow film with sharp Raman bands under 647.1 nm laser excitation at 627 cm⁻¹ (vCS), 1152 cm⁻¹ and 1236–1261 cm⁻¹ (vNN and vCN). The lack of electroactivity and short-lived photocurrents pointed to an insulating film at potentials up to 1.0 V (SHE). At more positive potentials, longer-lasting photocurrents were obtained, consistent with breakdown of the insulating film. XPS scans confirmed N:C:S ratios close to 1:1:1, with a deficiency of S of some 10% due to S lost as sulfate at the film surface. Oxidation of SeCN⁻ in neutral aqueous solution led to the formation of a less-stable orange paraselenocyanogen film with a Raman band at 1256–1267 cm⁻¹, which decomposed within a day to grey selenium. Received: 12 December 1997 / Accepted: 23 March 1998     

Stability of a microwave heated fluid Layer

When a time harmonic electromagnetic wave impinges on a slaba certain portion of the wave creates heat within the slab throughdipolar and ohmic heating. The electrical and thermal propertiesof the material dictate the dynamical nature of the heatingprocess, as well as the steady-state temperature profile. Thematerial considered here is a slab of fluid. We consider thecase where the fluid is bounded by thin rigid layers of transparentmaterial. The steady-state heating profile governs the typesof convective motions that can occur and also affects the stabilitycharacteristics of temperature, pressure and velocity perturbationsintroduced in the slab. The main objective here is to examinesuch stability characteristics, initially in the linear regime.Both rigid-rigid and rigid-free configurations are considered.     

Radical cyclization of sugar-derived beta-(alkynyloxy)acrylates: synthesis of novel fused ethers

[formula: see text] Tributyltin radical mediated cyclization of carbohydrate-derived beta-(alkynyloxy)acrylates leading to highly functionalized cis- and trans-fused bicyclic ethers of various ring sizes is described. The efficacy of the radical cyclization is nicely illustrated in the iterative construction of a trans-fused tricyclic tetrahydropyran.     

ICP-AES法测定内蒙古地区六种沙生木本植物中金属元素

采用ICP-AES法分别对内蒙古地区梭梭、小叶锦鸡儿、沙冬青、红柳、沙枣和沙柳等六种沙生木本植物中金属元素进行了测定和分析。该方法的加标回收率为94.98％～120.25％,RSD＜3.4％,具有良好的准确度和精密度。结果表明,常量元素Ca,K,Mg,Na,Al及植物生命活动所必需的微量元素Fe,Mn,Cu,Zn在六种沙生木本植物中表现为不同的含量顺序,且Fe,Mn,Cu,Zn四种元素的含量均低于陆生高等植物的平均含量。该测定结果为改善西部地区生态环境,选择优良防风固沙树种提供可靠的数据和理论依据。