Synthesis,solid-state crystal structure,and reactivity of a monomeric copper(I) anilido complex

Synthesis and isolation of the Cu(I) amido complex (dtbpe)Cu(NHPh) (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) is accomplished upon reaction of [(dtbpe)Cu(mu-Cl)](2) with LiNHPh. The anilido complex has been fully characterized by IR spectroscopy and multinuclear NMR spectroscopy as well as by single-crystal X-ray diffraction study. Salient features of the solid-state structure include an amido orientation that allows pi-interaction of the nitrogen-based lone pair with both the empty copper p-orbital and the pi-system of the phenyl substituent. A solid-state X-ray diffraction study of [(dtbpe)Cu(NH(2)Ph)][BF(4)] has allowed a direct comparison of the structural features upon conversion of the amine ligand to an amido. The reactivity of the amido ligand of (dtbpe)Cu(NHPh) is consistent with nucleophilic character. For example, the formation of Ph(3)CNHPh is observed upon treatment with [Ph(3)C][BF(4)], and reaction at room temperature with EtX (X = Br or I) yields N-ethylaniline. The reactivity of (dtbpe)Cu(NHPh) is compared to that of the octahedral and d(6) complex TpRu(PMe(3))(2)(NHPh) (Tp = hydridotris(pyrazolyl)borate).     

Synthesis and characterization of a family of structurally characterized dysprosium alkoxides for improved fatigue-resistance characteristics of PDyZT thin films

Using either an ammoniacal route, the reaction between DyCl3, Na0, and HOR in liquid ammonia, or preferentially reacting Dy(N(SiMe3)2)3 with HOR in a solvent, we isolated a family of dysprosium alkoxides as [Dy(mu-ONep)2(ONep)]4 (1), (ONep)2Dy[(mu3-ONep)(mu-ONep)Dy(ONep)(THF)]2(mu-ONep) (2), (ONep)2Dy[(mu3-ONep)(mu-ONep)Dy(ONep)(py)]2(mu-ONep) (3), [Dy3(mu3-OBut)2(mu-OBut3(OBut)4(HOBut)2] (4), [Dy3(mu3-OBut)2(mu-OBut)3(OBut)4(THF)2] (5), [Dy3(mu3-OBut)2(mu-OBut)3(OBut)4(py)2] (6), (DMP)Dy(mu-DMP)4[Dy(DMP)2(NH3)]2 (7), [Dy(eta6-DMP)(DMP)2]2 (8), Dy(DMP)3(THF)3 (9), Dy(DMP)3(py)3 (10), Dy(DIP)3(NH3)2 (11), [Dy(eta6-DIP)(DIP)2]2 (12), Dy(DIP)3(THF)2 (13), Dy(DIP)3(py)3 (14), Dy(DBP)3(NH3) (15), Dy(DBP)3 (16), Dy(DBP)3(THF) (17), Dy(DBP)3(py)2 (18), [Dy(mu-TPS)(TPS2]2 (19), Dy(TPS)3(THF)3 (20), and Dy(TPS)3(py)3 (21), where ONep = OCH2CMe3, OBut) = OCMe3, DMP = OC6H3(Me)(2)-2,6, DIP = OC6H3(CHMe2)(2)-2,6, DBP = OC6H3(CMe3)(2)-2,6, TPS = OSi(C6H5)3, tol = toluene, THF = tetrahydrofuran, and py = pyridine. We were not able to obtain X-ray quality crystals of compounds 2, 8, and 9. The structures observed and data collected for the Dy compounds are consistent with those reported for its other congeners. A number of these precursors were used as Dy dopants in Pb(Zr0.3Ti0.7)O3 (PZT 30/70) thin films, with compound 12 yielding the highest-quality films. The resulting Pb0.94Dy0.04(Zr0.3Ti0.7)O3 [PDyZT (4/30/70)] had similar properties to PZT (30/70), but showed substantial resistance to polarization reversal fatigue.     

Speciation in the AlCl3/SO2Cl2 catholyte system

The fundamental chemical behavior of the AlCl(3)/SO(2)Cl(2) catholyte system was investigated using (27)Al NMR spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction. Three major Al-containing species were found to be present in this catholyte system, where the ratio of each was dependent upon aging time, concentration, and/or storage temperature. The first species was identified as [Cl(2)Al(mu-Cl)](2) in equilibrium with AlCl(3). The second species results from the decomposition of SO(2)Cl(2) which forms Cl(2)(g) and SO(2)(g). The SO(2)(g) is readily consumed in the presence of AlCl(3) to form the crystallographically characterized species [Cl(2)Al(mu-O(2)SCl)](2) (1). For 1, each Al is tetrahedrally (T(d)) bound by two terminal Cl and two mu-O ligands whereas, the S is three-coordinated by two mu-O ligands and one terminal Cl. The third molecular species also has T(d)-coordinated Al metal centers but with increased oxygen coordination. Over time it was noted that a precipitate formed from the catholyte solutions. Raman spectroscopic studies show that this gel or precipitate has a component that was consistent with thionyl chloride. We have proposed a polymerization scheme that accounts for the precipitate formation. Further NMR studies indicate that the precipitate is in equilibrium with the solution.     

Stereochemical and mechanistic aspects of dioxygenase-catalysed benzylic hydroxylation of indene and chromane substrates

Toluene dioxygenase (TDO)-catalysed benzylic hydroxylation of indene substrates (8, 16 and 17), using whole cell cultures of Pseudomonas putida UV4, was found to yield inden-1-ol (14 and 22) and indan-1-one bioproducts (15 and 23). The formation of these bioproducts is consistent with the involvement of carbon-centred radical intermediates. TDO-catalysed oxidation of indenes 8 and 16 also gave cis-diols 13 and 18 respectively. TDO and naphthalene dioxygenase (NDO), used as both whole-cell preparations and as purified enzymes, were found to catalyse the benzylic hydroxylation of chromane 30, deuteriated (+/-)-chromane 30D and enantiomers (4S)-30D and (4R)-30D to yield (4R)- and (4S)-chroman-4-ols 31/31D respectively. The mechanism of benzylic hydroxylation of chromane 30/30D involves the stereoselective abstraction of a pro-R (with TDO) or a pro-S (with NDO) hydrogen atom at C-4 and a marked preference for retention of configuration.     

The chemical information system

The CIS is a collection of computerised data storage and retrieval components for chemical information, covering such aspects as structure, names, spectra, toxicology, hazards, literature references and molecular modeling. Each component is essentially a 'standalone' system but they share utility software and therefore composite searches within different databases are easily performed.     

Cadmium amido alkoxide and alkoxide precursors for the synthesis of nanocrystalline CdE (E = S, Se, Te)

The synthesis and characterization of a family of alternative precursors for the production of CdE nanoparticles (E = S, Se, and Te) is reported. The reaction of Cd(NR2)2 where NR2 = N(SiMe3)2 with n HOR led to the isolation of the following: n = 1 [Cd(mu-OCH2CMe3)(NR2)(py)]2 (1, py = pyridine), Cd[(mu-OC6H3(Me)(2)-2,6)2Cd(NR2)(py)]2 (2), [Cd(mu-OC6H3(CHMe2)(2)-2,6)(NR2)(py)]2 (3), [Cd(mu-OC6H3(CMe3)(2)-2,6)(NR2)(py)]2 (4), [Cd(mu-OC6H2(NH2)(3)-2,4,6)(NR2)(py)]2 (5), and n = 2 [Cd(mu-OC6H3(Me)(2)-2,6)(OC6H3(Me)(2)-2,6)(py)2]2 (6), and [Cd(mu-OC6H3(CMe3)(2)-2,6)(OC6H3(CMe3)(2)-2,6)(THF)]2 (7). For all but 2, the X-ray crystal structures were solved as discrete dinuclear units bridged by alkoxide ligands and either terminal -NR2 or -OR ligands depending on the stoichiometry of the initial reaction. For 2, a trinuclear species was isolated using four mu-OR and two terminal -NR2 ligands. The coordination of the Cd metal center varied from 3 to 5 where the higher coordination numbers were achieved by binding Lewis basic solvents for the less sterically demanding ligands. These complexes were further characterized in solution by 1H, 13C, and 113Cd NMR along with solid-state 113Cd NMR spectroscopy. The utility of these complexes as "alternative precursors" for the controlled preparation of nanocrystalline CdS, CdSe, and CdTe was explored. To synthesize CdE nanocrystals, select species from this family of compounds were individually heated in a coordinating solvent (trioctylphosphine oxide) and then injected with the appropriate chalcogenide stock solution. Transmission electron spectroscopy and UV-vis spectroscopy were used to characterize the resultant particles.     

The first stable mononuclear silyl palladium hydrides

The reaction of tertiary silanes with the low valent palladium complex [(mu-dcpe)Pd]2 affords equilibrium mixtures with mononuclear silyl palladium hydrides. These complexes have been characterized by NMR spectroscopy and, in one case, by X-ray crystallography. The silyl palladium hydride complexes rapidly interchange silicon and hydride coordination environments in solution which give rise to extraordinary temperature-dependent kinetic isotope effects for the fluxional process. An intermediate 2eta-Si-H complex is proposed for the interchange.     

Stress Measurements and Processing Optimization for Solution Derived SrBi2Ta2O9 Thin Films

The development of stress in the SrBi₂Ta₂O₉ (SBT) films generated from a chemical solution deposition method was monitored during processing using wafer curvature measurements. Stress measurements of the entire Si/SiO₂/Pt/SBT stack revealed an overall tensile stress of 536 MPa. The greatest increase in tensile stress was recorded for the anneal of the Pt bottom electrode and was due to the thermal expansion mismatch. Deposition of an amorphous SBT layer on the Pt, followed by a low temperature anneal (300°C), had little overall effect on the stress of the stack; however, upon crystallization, significantly more tensile stress was introduced into the stack. To further investigate the effect that stress has on the various electrical properties SBT films, wafers with different stress states were produced and SBT films deposited on them. Initial investigations indicate that SBT films on wafers with a higher tensile stress displayed improved ferroelectric hysteresis and switchable polarization.     

Tribasic lead maleate and lead maleate: synthesis and structural and spectroscopic characterizations

We report on the synthesis and structure of tribasic lead maleate hemihydrate ([Pb4O3]C2H2(CO2)2.(1/2)H2O, TRIMAL) and lead maleate (PbC2H2(CO2)2, PBMAL). The structure of [Pb4O3]C2H2(CO2)2.(1/2)H2O, solved ab initio from X-ray powder diffraction data, consists of infinite slabs of edge-sharing OPb4 tetrahedra, of composition [Pb4O3], running along the c axis and linked together into a three-dimensional network by tetradentate maleate anionic ligands. The structure of PbC2H2(CO2)2, solved from single crystal diffraction data, is lamellar and contains double layers of heptacoordinated lead atoms, bonded only to the oxygen atoms of the maleate ligands. In both compounds, lead is in the oxidation state 2+ and the coordination polyhedra around the Pb2+ exhibit a hemidirected geometry and are strongly distorted as a result of the lone pair of electrons. The absence of protons on the acidic portion of the maleate moieties was confirmed by Raman spectroscopy and by 1H MAS and 1H-13C CP MAS NMR experiments. The two compounds were further characterized using chemical and thermogravimetric analyses.     

Synthesis of the five-coordinate ruthenium(II) complexes [(PCP)Ru(CO)(L)][BAr'4] [PCP = 2,6-(CH2P(t)Bu2)2C6H3, BAr'4 = 3,5-(CF3)2C6H3, L = eta1-ClCH2Cl, eta1-N2, or mu-Cl-Ru(PCP)(CO)]: reactions with phenyldiazomethane and phenylacetylene

Reaction of (PCP)Ru(CO)(Cl) (1) with NaBAr'4 yields the bimetallic product [[(PCP)Ru(CO)](2)(mu-Cl)][BAr'4] (2). The monomeric five-coordinate complexes [(PCP)Ru(CO)(eta1-ClCH2Cl)][BAr'4] (3) and [(PCP)Ru(CO)(eta1-N2)][BAr'4] (4) are synthesized upon reaction of (PCP)Ru(CO)(OTf) (6) with NaBAr'4 in CH2Cl2 or C6H5F, respectively. The solid-state structures of 2, 3, and 4 have been determined by X-ray diffraction studies of single crystals. The reaction of 3 with PhCHN2 or PhCCH affords carbon-carbon coupling products involving the aryl group of the PCP ligand in transformations that likely proceed via the formation of Ru carbene or vinylidene intermediates. Density functional theory and hybrid quantum mechanics/molecular mechanics calculations were performed to investigate the bonding of weak bases to the 14-electron fragment [(PCP)Ru(CO)]+ and the energetics of different isomers of the product carbene and vinylidene complexes.