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At elevated pressure, stoichiometric and high quality Al2O3 thin films are fabricated at 65–105 °C. By using pre-organised single source precursor aluminium(III) diisopropylcarbamate, Al2O3 were deposited on the surface of a Si substrate in a single step in the liquid phase. Comprehensive removal of large carbamate ligands by proposed β-elimination during decomposition of precursor led to an effective delivery of enshrouded Al–O fragments. Scanning electron microscopy revealed dense and grainy surface morphology. The thicknesses of the films were measured to be 150–300 nm and independent to reaction temperatures or reaction times. Through the use of near edge X-ray absorption fine structure spectroscopy, Al absorption peaks suggest a short range crystalline formation in a film deposited at 105 °C.

Clean oriented Al2O3 thin film with a dominant Al2O3 plane was deposited on Si substrate at 550 °C, by single-source chemical vapor deposition (CVD) using aluminium(III) diisopropylcarbamate, Al2(O2CNiPr2)6. This process represents a substantial reduction in typical CVD film growth temperatures which are typically > 1000 °C. Through the studies of thermal stability of this precursor, we propose a specific β-elimination decomposition pathway to account for the low temperature of the precursor decomposition at the substrate, and for the lack of carbon impurity byproducts in the resulting alumina films that are characterized using X-ray photoelectron spectroscopy and depth profiling. © 2009 Elsevier B.V. All rights reserved.

A new series of (diisopropylcarbamato)(oxido)zinc complexes were obtained by innovative synthetic approaches. The (carbamato)zinc clusters [Zn4(μ4-O)(O2CNiPr2)6] (1) and [Zn8(μ4-O)2(O2CNiPr2)12] (2) were synthesised by an identical reaction procedure involving protolysis of ZnEt2 with iPr2NH/CO2 and followed by stoichiometric hydrolysis. Recrystallisation of the reaction product from nitrile solvents yielded the tetrazinc complex 1. Conversely, recrystallisation from alkane solvents yielded crystals of the octazinc complex 2. The two structural isomers were readily interconverted simply by recrystallisation from the appropriate solvent. Both complexes were structurally characterised by X-ray crystallography. The tetrazinc complex 1 has the quintessential basic zinc acetate type structure. Its dimer, the octazinc complex 2 is a new derivative of the [M8(μ4-O)2(O2CNiPr2)12] class, examples of which are known for all other first-row transition metals. The solution chemistry was investigated using variable-temperature NMR spectroscopy and ESI-MS. The new synthetic approach offers a route to other similar complexes. Thus, using Et2NH in place of iPr2NH yielded the known complex [Zn4(μ4-O)(O2CNEt2)6] (3).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A new range of barium complexes with single encapsulating ligands have been prepared for use in chemical vapour deposition (CVD). A novel pathway providing an unprecedented sequence of barium carbamates is reported. New dianionic bis β-ketoesterates and their barium, strontium and calcium derivatives were synthesised. High resolution mass spectrometry showed some barium derivatives to be monomeric, and preliminary testing indicated some volatility in these species. Calcium and strontium complexes were found to have nuclearities that varied according to their ionic radii relative to the chain length of the encapsulating ligand.

Zinc complexes of pyruvic and glyoxylic acid oximes have been investigated as potential precursors for single source chemical vapour deposition (SSCVD) of ZnO thin films. The X-ray crystal structures of the complexes and of their –NOMe analogues reveal markedly different coordination and intermolecular bonding patterns. These structural differences, in conjunction with ligand substituent changes impart different responses to thermogravimetric analysis (TGA), and sublimation. The glyoxylic acid methyloxime Zn(O2CCHN(OMe))2 · 2H2O has volatility and thermolysis properties suitable for SSCVD of ZnO.

Reaction of calix[4]arene with alkaline earth metals (Ca/Sr/Ba) in methanol followed by the addition of various titanium(IV) sources afforded novel dimeric 1:1 alkaline earth/titanium(IV) calix[4]arene complexes. In each complex the central core of the crystallographically imposed centrosymmetric dimer consists of a rhombus of alternating alkaline earth metals and μ3-oxo-centres. Five terminal methanol ligands form seven-coordinate calcium and strontium centres, while the barium centres are bridged by two additional methanol ligands, making them nine-coordinate. Each oxo centre is the apical ligand of a square-pyramidal titanium(IV) centre, whose basal plane ligands are the four phenolate oxygens from a calix[4]arene in the symmetrical cone-conformation. Deprotonation of calix[4]arene with potassium metal, followed by the addition of a titanium(IV) source containing at least one acetylacetonate ligand, formed a mixed potassium/titanium complex based on one calix[4]arene. The potassium cation in this complex binds within the π-basic calix[4]arene cavity, whilst titanium is octahedrally complexed in the exo-position, by four phenolates and one acetylacetonate. The alkaline earth titanium dimers and potassium/titanium monomers could be interconverted merely by changing the solvent, with the appropriate cations and ligands present in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

A novel precursor, hexakis[μ-(diethylcarbamato-O:O‘)]-μ4-oxotetrazinc, (Zn4O(CO2NEt2)6) (1), for the single source chemical vapor deposition (SSCVD) growth of ZnO films has been developed. The structure and chemistry of resultant films were characterized using photoemission spectroscopy and diffraction techniques as well as electron microscopy. The polycrystalline films are of relatively dense columnar structure and have preferred c-axis orientation. Their morphology is very similar to that of RF sputtered films, but with the significant difference that they do not exhibit the strain and stress usually inherent in as-deposited RF sputtered films. Film preparation using Zn4O(CO2NEt2)6 is therefore a simple one-step process with a lower overall production temperature required to produce high-quality films. Additionally, piezoelectric measurements of the films indicated piezoelectric responses close to that of single-crystalline ZnO.

The intercalation of Li into micro- and nanocrystalline anatase xerogel powders using n-butyllithium and various preparation conditions has been studied by 6Li and 7Li solid-state NMR and X-ray absorption spectroscopy. The orthorhombic lithium titanate phase which forms for Li/Ti 0.30. These two lithium environments are assigned to Li+ ions in similar structural sites that are uncoupled (species A) and weakly coupled (species B) to conduction band electrons. Nanocrystalline anatase samples produced by sol−gel methods differ from microcrystalline anatase in that the proportion of species A is greater. NMR further suggests that the coordination number of species A cannot be greater than five while no definite conclusions could be reached from NMR concerning species B. Titanium ...

The intercalation of Li into micro- and nanocrystalline anatase xerogel powders using n-butyllithium and various preparation conditions has been studied by 6Li and 7Li solid-state NMR and X-ray absorption spectroscopy. The orthorhombic lithium titanate phase which forms for Li/Ti 0.30. These two lithium environments are assigned to Li+ ions in similar structural sites that are uncoupled (species A) and weakly coupled (species B) to conduction band electrons. Nanocrystalline anatase samples produced by sol−gel methods differ from microcrystalline anatase in that the proportion of species A is greater. NMR further suggests that the coordination number of species A cannot be greater than five while no definite conclusions could be reached from NMR concerning species B. Titanium ...

Deprotonation of calix[6]arenes with barium in methanol followed by the addition of [Ti(OPr(i))(4)] or [Zr(OBu(n))(4)] is effective in the formation of novel dimeric 2:1 barium-titanium(IV)/zirconium(IV) calix[6]arene complexes. In these complexes a central Ti(IV)/Zr(IV) coordinated in the exo-position connects the two calix[6]arenes in the 1,3-alternate conformation, each with an endo-barium sharing common phenolate groups with the titanium/zirconium centre and participating in cation-pi interactions. A homometallic barium calix[6]arene dimer was also prepared wherein the calix[6]arenes are in the 1,3-alternate conformation with each coordinating one endo- and one exo-barium centre. The exo-barium cations connect the two calix[6]arenes through bridging methanol ligands. In this and the heterometallic complexes, cation-pi complexation of the Ba(2+) ion within the 1,3 alternate conformation of calix[6]arene facilitates the formation of the dimeric complexes in methanol. In contrast, the smaller Sr(2+) ion did not form similar complexes in methanol, and the formation of an analogous 2:1 strontium-titanium calixarene complex required the use of the more sterically demanding donor alcohol, isopropanol, the resulting complex being devoid of cation-pi interaction. The results show (i) that a subtle interplay of solvation strength, coordination array type and cavity/cation size influences the accessibility of heterobimetallic complexes based on calix[6]arenes, and (ii) a synergistic endo-exo binding behaviour.

Reaction of p-(t)Bu-calix[4]arene with dimethyl titanocene results in high yield selective 1,3-dimetallation of the calixarene in the cone conformation by selective cleavage of one methyl group.

Reaction of p-Bu(t)-calix[6]arene with barium metal in methanol then [Ti(OPr(i))4] affords a heterobimetallic complex with a central Ti(IV) attached to two calix[6]arenes in the 1,3-alternate conformation, each with an endo-barium sharing common phenolate groups with the titanium centre.

Lithiation of p-tBu-calix[4]arene followed by reaction with titanocene dichloride affords a novel tetranuclear titanium(IV) monocyclopentadienyl complex, wherein a single calix[4]arene in a cone conformation provides O-phenoxy coordination to four titanium atoms, with additional mu-oxo bridging between titanium centres in an eight membered ring.

Reaction of p-tBu-calix[6]arene with potassium metal in methanol followed by [TiCp2Cl2] affords novel mononuclear and binuclear monocyclopentadienyl titanium(IV) complexes, both having the same inverted double cone conformation with a Cp in one of the cavities, in both complexes.

Single source chemical vapour deposition (SSCVD) is a useful technique for preparing thin films, offering the simplicity of having all film components contained within the one molecule. However, the molecules currently used for SSCVD of MgO films are inconvenient due to high reactivity or expense. We report here the application of a novel hexameric diethylcarbamato complex Mg6(O2CNEt2)12 (1) as a single source precursor for MgO deposition. This precursor is simple to prepare, and has suitable volatility at moderate temperatures. SSCVD using 1 deposits high quality MgO films at deposition temperatures near 500 °C. Film analysis by XPS, XRD and SEM revealed a low carbon contamination and a film morphology that makes it suitable for use as a buffer layer between substrates and perovskite thin film coatings in electronic device construction.

The cover picture shows the structures of two new types of calix[4]arene complexes obtained by deprotonating the calixarene with an alkaline earth metal, or potassium metal, followed by reaction with selected titanium(IV) compounds. The alkaline earth metals form dimeric alkaline earth-titanium(IV) complexes, containing at the core a rhombus of alternating alkaline earth metal and μ3-oxo centres. Each oxo centre of the rhombic core is the apical ligand of a square-pyramidal titanium(IV) centre, whose basal plane donors are the four phenolate oxygen atoms from a calix[4]arene arrayed in the symmetrical cone conformation. Terminal methanol ligands surround the alkaline earth centres, and simultaneously hydrogen-bond to the adjacent phenolate oxygen atoms. Potassium reacts with calix[4]arene and the titanium(IV) source to give a monomeric mixed potassium-titanium complex. The potassium cation binds within the κ-basic calix[4]arene cavity, whilst the titanium centre is octahedrally complexed in the exo position by four phenolate and one acetylacetonate ligands. A solution pathway exists for the interconversion between the potassium-titanium calix[4]arene monomer and the alkaline earth-titanium dimers, where the product is dictated by the choice of solvent. Details are discussed in the article by R. N. Lamb et al. on p. 4153 ff.

Deprotonation of calix[4]arenes by alkali metal in methanol using simple benchtop procedures is effective in the formation of novel monomeric and dimeric titanium(IV) complexes. For the larger alkali metal cations, K+ and Cs+, favourable complexation within the π-basic calix[4]arene cavity facilitates the formation of monomeric titanium(IV) complexes when oligomer formation is inhibited by an acetylacetonate ligand. In contrast, the smaller Li+ and Na+ ions preferentially form dimeric complexes with exo-bridging alkali and titanium(IV) metal centres. A dimeric complex is also obtained for potassium in the absence of acetylacetonate. The solid state structures of the K–Ti and Na–Ti calix[4]arene dimer complexes show different structural characteristics depending on the nature of the alkali metal.

The complexes [Pd(η5-C5H5)L2]PF6[where L = PMe2Ph, PPh3, AsMe2Ph, AsPh3, or SbPh3 and L2=(SS)-, (RR,SS)-, (RS)-C6H4(PMePh)2-o or (SS)-, (RR,SS)-, (RS)-C6H4(AsMePh)2-o] have been prepared in high yield from the appropriate complexes [PdCl2L2] and cyclopentadiene in Me2CO in the presence of AgPFe6, or with AgNO3 followed by metathesis with NH4PF6. The brightly coloured compounds conduct as uni-univalent electrolytes in Me2CO and CH2Cl2 and have spectroscopic properties consistent with η5 co-ordination of the cyclopentadienyl moiety in solution. The molecular structure of [Pd(η5-C5H5)(SbPh3)2]PF6·CH2Cl2 has been determined by a single-crystal X-ray analysis. The crystals are monoclinic, space group P21/c with a= 12.506(6), b= 19.002(7), c= 18.575(5)A, β= 106.53(3)°, and Z= 4. The structure was solved by heavy-atom methods at 295(1) K and refined by least-squares methods to R= 0.051 for 4 384 observed reflections. The arrangement of the two antimony atoms and the centre of the cyclopentadienyl ring about the palladium atom is approximately trigonal. The co-ordinated cyclopentadienyl moiety shows no significant deviations from planarity.

On etudie l'echange selectif des protons methylenes d'un coordinat glycine coordine. On montre aussi que la vitesse de l'echange peut etre employee pour produire de la glycine chirale a n'importe quel degre de purete chirale. Le systeme choisi est [Co((S,S)-proam)(picgly)] + un complexe de Co(III) contenant 2 coordinats tridentes dont l'un contient un reste glycine (proam=iminodimethylene-2,2' bis-pyrrolidine; picgly=N-picolinoylglycine)

The crystal structures of the title compounds, C6H4(PMePh)2(1) and [C6H4(PMePhH)(PMePh)][BF4](2), have been determined by single-crystal X-ray diffraction methods at 295 K and refined by least squares to residuals of 0.044(1)(1 726 ‘observed’ reflections) and 0.045(2)(1 755). Crystals of (1) are monoclinic, space group P21/n, with a 14.604(8), b 10.181(6), c 12.868(9)A, β 110.94(5)°, and Z= 4; those of (2) are triclinic, P, with a 12.594(5), b 9.988(4), c 8.643(4)A, α 81.69(3), β 87.62(3), γ 70.85(3)° and Z= 2. In (1), 〈P–C〉 is 1.839A and 〈C–P–C〉 100·7°; in (2), the corresponding values about one of the phosphorus atoms are 1.835A and 102·2°, but about the other, 1.789A and 110·0°, and it is tentatively proposed that the proton is bonded to the latter. The anion in (2) is disordered.

A comparative investigation of the mass spectra of the compounds Me2PhE, MePh2E, MeEtPhE (where E = P, As or Sb), PhPriEH (where E = N, P or As), MePhAsH, MePhEX (where X = Cl or I and E = As; X = Br and E = Sb) and PhPriEX (where X = Cl and E = P or As) has been undertaken at 70 eV. The main fragmentation pathways have been determined and the criteria established for the interpretation of spectra of these simple derivatives applied to a series of more complex arsines.

The dissymmetric chelating agent (RR,SS)-ortho-phenylenebis(methylphenylarsine) has been resolved into its enantiomers by fractionally crystallising internally diastereoisomeric palladium complexes containing the ditertiary arsine and optically active ortho-metallated dimethyl(α-methylbenzyl)amine. The full procedure is described and constitutes the first satisfactory route to optically active ditertiary arsines containing asymmetric arsenic atoms. The optically active ditertiary arsines, α(589 nm, CH2Cl2)± 95°, are air-stable crystalline solids, m.p. 75–76 °C, and the absolute configuration of the enantiomer with a positive rotation at the sodium D line (589 nm) has been established as RR by a single-crystal X-ray determination of the structure of the internally diastereoisomeric palladium complex containing (S)(–)-dimethyl(α-methylbenzyl)amine. The meso diastereoisomer undergoes a halide-ion assisted epimerisation in acidic methanol solution and may be converted, under suitable conditions, into the less soluble racemic diastereoisomer thereby effecting a second-order asymmetric transformation between the diastereoisomeric ditertiary arsines.

The dissymmetric chelating agent (RR,SS)-ortho-phenylenebis(methylphenylarsine) has been resolved into its enantiomers by fractionally crystallising internally diastereoisomeric palladium complexes containing the ditertiary arsine and optically active ortho-metallated dimethyl(α-methylbenzyl)amine. The full procedure is described and constitutes the first satisfactory route to optically active ditertiary arsines containing asymmetric arsenic atoms. The optically active ditertiary arsines, α(589 nm, CH2Cl2)± 95°, are air-stable crystalline solids, m.p. 75–76 °C, and the absolute configuration of the enantiomer with a positive rotation at the sodium D line (589 nm) has been established as RR by a single-crystal X-ray determination of the structure of the internally diastereoisomeric palladium complex containing (S)(–)-dimethyl(α-methylbenzyl)amine. The meso diastereoisomer undergoes a halide-ion assisted epimerisation in acidic methanol solution and may be converted, under suitable conditions, into the less soluble racemic diastereoisomer thereby effecting a second-order asymmetric transformation between the diastereoisomeric ditertiary arsines.

A comparative investigation of the mass spectra of the compounds Me2PhE, MePh2E, MeEtPhE (where E = P, As or Sb), PhPriEH (where E = N, P or As), MePhAsH, MePhEX (where X = Cl or I and E = As; X = Br and E = Sb) and PhPriEX (where X = Cl and E = P or As) has been undertaken at 70 eV. The main fragmentation pathways have been determined and the criteria established for the interpretation of spectra of these simple derivatives applied to a series of more complex arsines.

Ylides derived from optically active arsonium salts react with aromatic aldehydes to give trans-2,3-diaryl-oxirans in high chemical yields and with optical purities of between 4·7 and 38%.

The crystal structure of the title compound, [Tl(S2CNEt2)3], has been determined by single-crystal X-ray diffraction methods at 295 K and refined by full-matrix least squares to a residual of 0.050 for 2517 'observed' reflections. Crystals are monoclinic, with space group A2/a, a 14.789(7), b 10.428(4), c 18.207(9) Ǻ, β 118.11(4)°, Z 4, and are isostructural with those of the previously determined gallium and indium analogues, the molecule having 2 symmetry with 2.666 Ǻ. As in the dimethyl/thallium analogue, the departure of the TlS6 core symmetry from 3 is large and is examined in terms of electron-pair repulsion theory.

The crystal structures of the title compounds, C6H4(PMePh)2(1) and [C6H4(PMePhH)(PMePh)][BF4](2), have been determined by single-crystal X-ray diffraction methods at 295 K and refined by least squares to residuals of 0.044(1)(1 726 ‘observed’ reflections) and 0.045(2)(1 755). Crystals of (1) are monoclinic, space group P21/n, with a 14.604(8), b 10.181(6), c 12.868(9)A, β 110.94(5)°, and Z= 4; those of (2) are triclinic, P, with a 12.594(5), b 9.988(4), c 8.643(4)A, α 81.69(3), β 87.62(3), γ 70.85(3)° and Z= 2. In (1), 〈P–C〉 is 1.839A and 〈C–P–C〉 100·7°; in (2), the corresponding values about one of the phosphorus atoms are 1.835A and 102·2°, but about the other, 1.789A and 110·0°, and it is tentatively proposed that the proton is bonded to the latter. The anion in (2) is disordered.