NiN(2)S(2) complexes as metallodithiolate ligands to Rh(I), Rh(II) and Rh(III)

Three molecular structures are reported which utilize the NiN(2)S(2) ligands -, (bis(mercaptoethyl)diazacyclooctane)nickel and -', bis(mercaptoethyl)diazacycloheptane)nickel, as metallodithiolate ligands to rhodium in oxidation states i, ii and iii. For the Rh(I) complex, the NiN(2)S(2) unit behaves as a bidentate ligand to a square planar Rh(I)(CO)(PPh(3))(+) moiety with a hinge or dihedral angle (defined as the intersection of NiN(2)S(2) and S(2)Rh(C)(P) planes) of 115 degrees . Supported by -' ligands, the Rh(II) oxidation state occurs in a dirhodium C(4) paddlewheel complex wherein four NiN(2)S(2) units serve as bidentate bridging ligands to two singly-bonded Rh(II) ions at 2.893(8) A apart. A compilation of the remarkable range of M-M distances in paddlewheel complexes which use NiN(2)S(2) complexes as paddles is presented. The Rh(III) state is found as a tetrametallic [Rh(-')(3)](3+) cluster, roughly shaped like a boat propeller and structurally similar to tris(bipyridine)metal complexes.     

Chemical and Electrochemical Asymmetric Dihydroxylation of Olefins in I(2)-K(2)CO(3)-K(2)OsO(2)(OH)(4) and I(2)-K(3)PO(4)/K(2)HPO(4)-K(2)OsO(2)(OH)(4) Systems with Sharpless' Ligand

Iodine-assisted chemical and electrochemical asymmetric dihydroxylation of various olefins in I(2)-K(2)CO(3)-K(2)OsO(2)(OH)(4) and I(2)-K(3)PO(4)/K(2)HPO(4)-K(2)OsO(2)(OH)(4) systems with Sharpless' ligand provided the optically active glycols in excellent isolated yields and high enantiomeric excesses. Iodine (I(2)) was used stoichiometrically for the chemical dihydroxylation, and good results were obtained with nonconjugated olefins in contrast to the case of potassium ferricyanide as a co-oxidant. The potentiality of I(2) as a co-oxidant under stoichiometric conditions has been proven to be effective as an oxidizing mediator in electrolysis systems. Iodine-assisted asymmetric electro-dihydroxylation of olefins in either a t-BuOH/H(2)O(1/1)-K(2)CO(3)/(DHQD)(2)PHAL-(Pt) or t-BuOH/H(2)O(1/1)-K(3)PO(4)/K(2)HPO(4)/(DHQD)(2)PHAL-(Pt) system in the presence of potassium osmate in an undivided cell was investigated in detail. Irrespective of the substitution pattern, all the olefins afforded the diols in high yields and excellent enantiomeric excesses. A plausible mechanism is discussed on the basis of cyclic voltammograms as well as experimental observations.     

Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)] x [HO(2)C-C(6)H(4)-CO(2)H](x) x H(2)O(y)

The first three-dimensional chromium(III) dicarboxylate, MIL-53as or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)].[HO(2)C-C(6)H(4)-CO(2)H](0.75), has been obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)]. At room temperature, MIL-53ht adsorbs atmospheric water immediately to give Cr(III)(OH) x [O(2)C-C(6)H(4)-CO(2)] x H(2)O or MIL-53lt (lt: low-temperature form, ht: high-temperature form). Both structures, which have been determined by using X-ray powder diffraction data, are built up from chains of chromium(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of one-dimensional large pore channels filled with free disordered terephthalic molecules (MIL-53as) or water molecules (MIL-53lt); when the free molecules are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m(2)/g. The transition between the hydrated form (MIL-53lt) and the anhydrous solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 A), the pores being clipped in the presence of water molecules (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids has been investigated using TGA and X-ray thermodiffractometry. The sorption properties of MIL-53lt have also been studied using several organic solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Néel temperatures T(N) of 65 and 55 K, respectively. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a = 17.340(1) A, b = 12.178(1) A, c = 6.822(1) A, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a = 16.733(1) A, b = 13.038(1) A, c = 6.812(1) A, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a = 19.685(4) A, b = 7.849(1) A, c = 6.782(1) A, beta = 104.90(1) degrees, and Z = 4.     

Nanostructured Ti(1-x)S(x)O(2-y)N(y) heterojunctions for efficient visible-light-induced photocatalysis

Highly visible-light-active S,N-codoped anatase-rutile heterojunctions are reported for the first time. The formation of heterojunctions at a relatively low temperature and visible-light activity are achieved through thiourea modification of the peroxo-titania complex. FT-IR spectroscopic studies indicated the formation of a Ti(4+)-thiourea complex upon reaction between peroxo-titania complex and thiourea. Decomposition of the Ti(4+)-thiourea complex and formation of visible-light-active S,N-codoped TiO(2) heterojunctions are confirmed using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and UV/vis spectroscopic studies. Existence of sulfur as sulfate ions (S(6+)) and nitrogen as lattice (N-Ti-N) and interstitial (Ti-N-O) species in heterojunctions are identified using X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopic techniques. UV-vis and valence band XPS studies of these S,N-codoped heterojunctions proved the fact that the formation of isolated S 3p, N 2p, and Π* N-O states between the valence and conduction bands are responsible for the visible-light absorption. Titanium dioxide obtained from the peroxo-titania complex exists as pure anatase up to a calcination temperature as high as 900 °C. Whereas, thiourea-modified samples are converted to S,N-codoped anatase-rutile heterojunctions at a temperature as low as 500 °C. The most active S,N-codoped heterojunction 0.2 TU-TiO(2) calcined at 600 °C exhibits a 2-fold and 8-fold increase in visible-light photocatalytic activities in contrast to the control sample and the commercial photocatalyst Degussa P-25, respectively. It is proposed that the efficient electron-hole separation due to anatase to rutile electron transfer is responsible for the superior visible-light-induced photocatalytic activities of S,N-codoped heterojunctions.     

Cyclotriphosphazene hydrazides as efficient multisite coordination ligands. eta(3)-fac-non-geminal-N(3) coordination of spiro-N(3)P(3)[O(2)C(12)H(8)][N(Me)NH(2)](4) (L) in L(2)CoCl(3) and L(2)M(NO(3))(2) (M = Ni, Zn, Cd)

The cyclophosphazene tetrahydrazide spiro-N(3)P(3)[O(2)C(12)H(8)][N(Me)NH(2)](4) (L) functions as a multisite coordination ligand and affords L(2)CoCl(3).2CH(3)OH (4), L(2)Ni(NO(3))(2).2CHCl(3).2.5H(2)O (5), L(2)Zn(NO(3))(2).2CH(3)CN.2H(2)O (6), and L(2)Cd(NO(3))(2) (7). Each of the cyclophosphazene ligands that is involved in coordination to the metal functions as a non-geminal-N(3) donor coordinating through one ring nitrogen atom and two non-geminal-NH(2) nitrogen atoms. The coordination geometry around the metal ion in 4-6 is approximately octahedral while it is severely distorted in the case of 7.     

Single-crystal Al(18)B(4)O(33) microtubes

Aluminum borate microtubes were prepared in excellent yield by annealing the Al(2)O(3)-NaBH(4)-NiCl(2) starting materials at 1050 degrees C under N(2)(H(2)) atmosphere. The tubes are usually open at each end with the outer diameters narrowly distributed at ca. 1 microm. XRD results and TEM analysis identified the composition of these tubes as single-crystal orthorhombic Al(18)B(4)O(33). These newly discovered ceramic microtubes with open ends have a variety of promising applications such as being filled with other materials for protection or for the fabrication of novel composites or filtering media.     

(h4-Dibenzylideneacetone)pentamethylcyclopentadienylrhodium(I)

dibenzylideneacetone can act as a 1,4-diene in bonding to a single metal atom and this has been shown by the synthesis of (h⁴-dibenzylideneacetone)pentamethylcyclopentadienylrhodium(I).     

AN N-BONDED Cu(I) THIOCYANATE COMPLEX: ISOTHIOCYANATO-(1,1,1,-TRIS(DIPHENYL-PHOSPHINOMETHYL)ETHANE) COPPER(I)

Abstract

The complex [Cu(((C₆ H₅)₂ PCH₂)₃ CCH₃) (NCS)] has been prepared and characterized by infrared, PMR, and X-ray photoelectron spectroscopy. It has been formulated as a mixture of N- and S-bonded isomers in the solid state, the ratio of the isomers depending on the conditions of isolation of the complex as well as the sampling technique used for the infrared spectral measurements (i.e., mull vs. KBr pellet). In CHCl₃ solution the complex exists exclusively as the N-bonded isomer, although PMR spectroscopy indicates that a rapid exchange of the phosphorus sites of the ligand occurs at room temperature.

The complex [Cu(P(C₆ H₅)₃)₂ SCN]₂, in contrast, is formulated as a dimeric species in the solid state with two bridging thiocyanates. In CHCl₃ solution, however, the bridges cleave to give exclusively the N-bonded monomeric three-coordinate complex.     

Synthesis of the C(29)-C(45) bis-pyran subunit (E-F) of spongistatin 1 (Altohyrtin A)

A synthesis of the C(29)-C(45) bis-pyran subunit 2 of spongistatin 1 (1a) is described. The synthesis proceeds in 19 steps from the chiral aldehyde ent-7, and features highly diastereoselective alpha-alkoxyallylation reactions using the gamma-alkoxy substituted allylstannanes 17 and 19, as well as a thermodynamically controlled intramolecular Michael addition to close the F-ring pyran. The E ring was assembled via the Mukaiyama aldol reaction of F-ring methyl ketone 3 and the 2,3-syn aldehyde 4.     

Hexaaquacobalt(II) bis(hypophosphite) and hexaaquacobalt(II)/nickel(II) bis(hypophosphite)

The title compounds, hexa­aqua­cobalt(II) bis­(hypophosphite), [Co(H₂O)₆](H₂­PO₂)₂, and hexa­aqua­cobalt(II)/nickel(II) bis(hypophosphite), [Co_0.5Ni_0.5(H₂O)₆](H₂PO₂)₂, are shown to adopt the same structure as hexa­aqua­magnesium(II) bis­(hypophosphite). The packing of the Co(Ni) and P atoms is the same as in the structure of CaF₂. The Co^II(Ni^II) atoms have a pseudo‐face‐centred cubic cell, with a = b～ 10.3 Å, and the P atoms occupy the tetrahedral cavities. The central metal cation has a slightly distorted octahedral coordination sphere. The geometry of the hypophosphite anion in the structure is very close to ideal, with point symmetry mm2. Each O atom of the hypophosphite anion is hydrogen bonded to three water mol­ecules from different cation complexes, and each H atom of the hypophosphite anion is surrounded by three water mol­ecules from further different cation complexes.     

A full interionic potential for Na(1+x)Zr(2)Si(x)P(3-x)O(12) superionic conductors

Most inorganic solids are made up of octahedral and tetrahedral units interconnected to give an infinite framework. Use of computer simulation to study these materials has not been as prevalent as in the organic or biomolecules. Na(1+x)Zr(2)Si(x)P(3-x)O(12) is a typical inorganic solid with ZrO(6) octahedra and (Si/P)O(4) tetrahedra which are shown along with a few Na(+) sites marked M1, M2, and M3. We report here a full interionic potential which reproduces the structure and conductivity of these solids. This augurs well for the study of other inorganic solids.     

Bis(acetylacetonato)tricarbonyl tungsten(II): a convenient precursor to chiral bis(acac) tungsten(II) complexes

Two equivalents of acetylacetonate (acac) have been successfully introduced into a monomeric tungsten(II) coordination sphere. With the tetracarbonyltriiodotungsten(II) anion as a precursor, the formation of a tungsten(II) bis(acac) tricarbonyl complex, W(CO)3(acac)2, 1, has been accomplished. The addition of PMe3 or PMe2Ph to tricarbonyl complex 1 formed tungsten(II)bis(acac)dicarbonylphosphine complexes 2a and 2b, respectively. Single-crystal X-ray diffraction studies of the parent tricarbonyl complex, 1, and dicarbonyl trimethylphosphine complex 2a confirmed seven-coordinate geometries for both complexes. Variable-temperature 1H and 13C{1H} NMR spectroscopy revealed fluxional behavior for these seven-coordinate molecules: rapid exchange of the three carbon monoxide ligands in 1 was observed, and movement of the phosphine ligand through a mirror plane in a C(S) intermediate species was observed for both 2a and 2b. Tricarbonyl complex 1 reacted readily with alkyne reagents to form bis(acac)monocarbonylmonoalkynetungsten(II) complexes 3a (PhC(triple bond)CH) and 3b (MeC(triple bond)CMe). Variable-temperature 1H NMR spectroscopy was used to probe rotation of the alkyne ligand in 3a and 3b. The introduction of two alkyne ligands was accomplished thermally using excess PhC(triple bond)CPh to form bis(alkyne) complex 4 which was characterized crystallographically, as well as by 1H and 13C NMR spectroscopy. The availability of W(CO)3(acac)2 as a source of the W(acac)2 d4 moiety lies at the heart of the chemistry reported here.     

Photoionization of tetrakis(pyrophosphito)diplatinum(II)

Hydrated electrons are produced by photoexcitation of aqueous solutions of a binuclear platinum(II) complex, Pt₂(POP)⁴⁻₄. Studies of yields of e⁻_aq as a function of laser energy indicate that the electrons are liberated by a two-photon process. The efficiency of production of e⁻_aq relative to that of the Pt(II) triplet can be as high as 0.15.     

Order parameters based on (13)C(1)H, (13)C(1)H(2) and (13)C(1)H(3) heteronuclear dipolar powder patterns: a comparison of MAS-based solid-state NMR sequences

Order parameters describing conformational exchange processes on the nanosecond to microsecond timescale can be obtained from powder patterns in solid-state NMR (SSNMR) experiments. Extensions of these experiments to magic-angle spinning (MAS) based high-resolution experiments have been demonstrated, which show a great promise for site-specific probes of biopolymers. In this study, we present a detailed comparison of two pulse sequences, transverse Manfield-Rhim-Elleman-Vaughn (T-MREV) and Lee-Goldburg cross-polarization (LGCP), using experimental and simulation tools to explore their utility in the study of order parameters. We discuss systematic errors due to passively coupled (13)C or (1)H nuclei, as well as due to B(1) inhomogeneity. Both pulse sequences can provide quantitative measurements of the order parameter, but the LGCP experiment is capable of greater accuracy provided that the B(1) field is highly homogeneous. The T-MREV experiment is far better compensated for B(1) inhomogeneity, and it also performs better in situations with limited signal.     

Phosphine-boranes as bidentate ligands: formation of [8,8-eta(2)-(eta(2)-(BH(3)).dppm)-nido-8,7-RhSB(9)H(10)] and [9,9-eta(2)-(eta(2)-(BH(3)).dppm)-nido-9,7,8-RhC(2)B(8)H(11)] from [8,8-(eta(2)-dppm)-8-(eta(1)-dppm)-nido-8,7-RhSB(9)H(10)] and [9,9-(eta(2)-dppm)-9-(eta(1)-dppm)-nido-9,7,8-RhC(2)B(8)H(11)], respectively

The two clusters [8,8-(eta(2)-dppm)-8-(eta(1)-dppm)-nido-8,7-RhSB(9)H(10)] (1) and [9,9-(eta(2)-dppm)-9-(eta(1)-dppm)-nido-9,7,8-RhC(2)B(8)H(11)] (2) (dppm = PPh(2)CH(2)PPh(2)), both of which contain pendant PPh(2) groups, react with BH(3).thf to afford the species [8,8-eta(2)-(eta(2)-(BH(3)).dppm)-nido-8,7-RhSB(9)H(10)] (3) and [9,9-eta(2)-(eta(2)-(BH(3)).dppm))-nido-9,7,8-RhC(2)B(8)H(11)] (4), respectively. These two species are very similar in that they both contain the bidentate ligand [(BH(3)).dppm], which coordinates to the Rh center via a PPh(2) group and also via a eta(2)-BH(3) group. Thus, the B atom in the BH(3) group is four-coordinate, bonded to Rh by two bridging hydrogen atoms, to a terminal H atom, and to a PPh(2) group. At room temperature, the BH(3) group is fluxional; the two bridging H atoms and the terminal H atom are equivalent on the NMR time scale. The motion is arrested at low temperature with DeltaG++ = ca. 37 and 42 kJ mol(-1), respectively, for 3 and 4. Both species are characterized completely by NMR and mass spectral measurements as well as by elemental analysis and single-crystal structure determinations.     

6-甲基-4-羟基-喹啉酸盐羟基钒(V)(英文)

V anadium髨coordination com pound1is achievedby the hydrotherm al reaction of V2O5and ethyl6-m ethyl-4-hydroxy-3-quinolinecarboxylate(em hq)w ithwater as solvent.X-ray single crystal diffraction studyof com pound1(Fig.1)shows that com pound1crystal-lizes …     

Polydentate N(2)S(2)O and N(2)S(2)O(2) Ligands as Alcoholic Derivatives of (N,N'-Bis(2-mercaptoethyl)-1,5-diazacyclooctane)nickel(II) and (N,N'-Bis(2-mercapto-2-methylpropane)-1,5-diazacyclooctane)nickel(II)

The synthesis, structural characterization, spectroscopic, and electrochemical properties of N(2)S(2)-ligated Ni(II) complexes, (N,N'-bis(2-mercaptoethyl)-1,5-diazacyclooctane)nickel(II), (bme-daco)Ni(II), and (N,N'-bis(2-mercapto-2-methylpropane)1,5-diazacyclooctane)nickel(II), (bme-daco)Ni(II), derivatized at S with alcohol-containing alkyl functionalities, are described. Reaction of (bme-daco)Ni(II) with 2-iodoethanol afforded isomers, (N,N'-bis(5-hydroxy-3-thiapentyl)-1,5-diazacyclooctane-O,N,N',S,S')halonickel(II) iodide (halo = chloro or iodo), 1, and (N,N'-bis(5-hydroxy-3-thiapentyl)-1,5-diazacyclooctane-N,N',S,S')nickel(II) iodide, 2, which differ in the utilization of binding sites in a potentially hexadentate N(2)S(2)O(2) ligand. Blue complex 1 contains nickel in an octahedral environment of N(2)S(2)OX donors; X is best modeled as Cl. It crystallizes in the monoclinic space group P2(1)/n with a = 12.580(6) ?, b = 12.291(6) ?, c = 13.090(7) ?, beta = 97.36(4) degrees, and Z = 4. In contrast, red complex 2 binds only the N(2)S(2) donor set forming a square planar nickel complex, leaving both -CH(2)CH(2)OH arms dangling; the iodide ions serve strictly as counterions. 2 crystallizes in the orthorhombic space group Pca2(1) with a = 15.822(2) ?, b = 13.171(2) ?, c = 10.0390(10) ?, and Z = 4. Reaction of (bme-daco)Ni(II) with 1,3-dibromo-2-propanol affords another octahedral Ni species with a N(2)S(2)OBr donor set, ((5-hydroxy-3,7-dithianonadiyl)-1,5-diazacyclooctane-O,N,N',S,S')bromonickel(II) bromide, 3. Complex 3 crystallizes in the orthorhombic space group Pca2(1) with a = 15.202(5) ?, b = 7.735(2) ?, c = 15.443(4) ?, and Z = 4. Complex 4.2CH(3)CN was synthesized from the reaction of (bme-daco)Ni(II) with 1,3-dibromo-2-propanol. It crystallizes in the monoclinic space group P2/c with a = 20.348(5) ?, b = 6.5120(1) ?, c = 20.548(5) ?, and Z = 4.     

6-甲基-4-羟基-喹啉酸盐羟基钒(Ⅴ)(英)

The central V atom in bis[6-methyl-4-hydroxy-3-quinolinecarboxylate] mono(oxo)mono-hydroxy-vanadium(Ⅴ) (1), synthesized by the hydrothermal treatment of ethyl 6-methyl-4-hydroxy-3-quinolinecarboxylate and V₂O₅, has a distorted octahedral coordination geometry formed by six oxygen atoms from two oxygen atom of two hydroxy groups and two oxygen atoms of two carboxylate groups as well as one oxo group and hydroxy group. CCDC: 285592.     

Durability prediction of p-urethane clearcoats using infrared p(hoto) a(coustic) s(pectroscopy)

The durability of topcoats is dependent on a large number of factors as polymer composition, stabilization package and the conditions during the weathering process. For obvious reasons prediction of the long-term (5-10 year) durability of coatings is very important. The rate-determining factor for the degradation of PUR coatings is photo-oxidation. The photo-oxidation rate is controlled by the polymer structure but also stabilizers as HALS has a large influence. The prediction of the durability of clearcoats is based on tracing of the photo-oxidation rate and of the HALS longevity during exposure. The photo-oxidation rate is measured using FTIR-PAS. The results show that degradation can be detected much earlier compared with classical methods as gloss loss. Moreover detection of differences between systems after short exposure times as well as prediction of the long-term durability are possible.     

ENHANCED WATER SORPTION OF A SEMI-INTERPENETRATING POLYMER NETWORK (IPN) OF POLY(2-HYDROXYETHYL METHACRYLATE) (PHEMA) AND POLY(ETHYLENE GLYCOL) (PEG)

ABSTRACT

An attempt was made to enhance the water-sorption capacity of polymers of 2-hydroxyethyl methacrylate (HEMA) by preparing its semi-interpenetrating polymer network (IPN) with a hydrophilic polymer such as poly(ethylene glycol) (PEG). The effects of various factors, such as history of the polymer sample, chemical architecture of the IPN, presence of salt ions in the swelling medium, and temperature of the swelling medium, were investigated on the water sorption kinetics of the IPNs. The IPN was characterized by IR spectral analysis and various structural parameters, such as molecular weight between crosslinks (M_c), crosslink density (q) and number of elastically effective chains (V_e), were evaluated. The IPNs were also assessed for their antithrombogenic potential.