Showing papers by "Gillian Reid published in 2013"

Medium and high oxidation state metal/non-metal fluoride and oxide–fluoride complexes with neutral donor ligands

Abstract: While most high and medium oxidation state (O.S. ≥ 3) metal and non-metal fluorides and oxide fluorides are strong Lewis acids, exploration of their coordination chemistry with neutral ligands has been limited and mostly non-systematic. This is despite the very different properties conferred on the acceptor centre by the small electronegative fluoride ligands compared to the heavier halides. This article sets out these key differences, discusses possible synthetic routes, the key characterisation techniques, and appropriate bonding models. Current knowledge of the coordination chemistry of d, f and p-block fluorides and oxide fluorides with neutral ligands (with donor atoms drawn from Groups 15 and 16 and including N-heterocyclic carbenes) is then presented and discussed, and the differences in properties compared to complexes containing the heavier halides are illustrated. The emphasis is on work published post 1990, but earlier work is also included as essential background and where no more recent information exists. Attention is drawn to unexplored areas meriting investigation and to possible applications of these complexes.

Non-aqueous electrodeposition of p-block metals and metalloids from halometallate salts

Abstract: A versatile electrochemical system for the non-aqueous electrodeposition of crystalline, oxide free p-block metals and metalloids is described, and it is demonstrated that by combining mixtures of these reagents, this system is suitable for electrodeposition of binary semiconductor alloys. The tetrabutylammonium halometallates, [NnBu4][InCl4], [NnBu4][SbCl4], [NnBu4][BiCl4], [NnBu4]2[SeCl6] and [NnBu4]2[TeCl6], are readily dissolved in CH2Cl2 and form reproducible electrochemical systems with good stability in the presence of a [NnBu4]Cl supporting electrolyte. The prepared electrolytes show a wide potential window and the electrodeposition of indium, antimony, bismuth, tellurium and selenium on glassy carbon and titanium nitride electrodes has been demonstrated. The deposited elements were characterised by scanning electron microscopy, energy dispersive X-ray analysis and powder X-ray diffraction. The compatibility of the reagents permits the preparation of a single electrolyte containing several halometallate species which allows the electrodeposition of binary materials, as is demonstrated for InSb. This room temperature, ‘bottom-up’ electrochemical approach should thus be suitable for the one-pot deposition of a wide range of compound semiconductor materials.

Tin(II) fluoride vs. tin(II) chloride--a comparison of their coordination chemistry with neutral ligands

Abstract: Reaction of SnF2 in MeOH with the appropriate neutral N- or O-donor ligands produces [SnF(2,2′-bipy)]2SnF6, [SnF(1,10-phen)]2SnF4 and [SnF2(L)] L = Me3PO, dmso or pyNO). The X-ray structures of [SnF(2,2′-bipy)]2SnF6, [SnF(1,10-phen)]2SnF4 and [SnF2(dmso)], reveal trigonal pyramidal Sn(II) cores with longer fluorine bridges completing distorted 5- or 6-coordination. Attempts to prepare SnF2 adducts with various phosphine or diphosphine ligands in MeCN failed, whilst in CH2Cl2 solution complex reactions involving the solvent occurred. The NHC, 1,3-(2,6-di-isopropylphenyl)imidazol-2-ylidene (IDiPP) and SnF2 produced the imidazolium salt, [IDiPPH]SnF3, the crystal structure of which revealed the first example of a discrete trifluorostannate(II) ion. In contrast, diphosphine complexes of tin(II) chloride formed readily, including [SnCl2{Me2P(CH2)2PMe2}], [SnCl2{o-C6H4(PMe2)2}], [SnCl2{o-C6H4(PPh2)2}] and [(SnCl2)2(μ-Ph2P(CH2)2PPh2)], which were characterised by X-ray crystallography. The structures of [SnCl2{Me2P(CH2)2PMe2}] and [SnCl2{o-C6H4(PMe2)2}] reveal chloride-bridged dimers, but [SnCl2{o-C6H4(PPh2)2}], although also dimeric, has very asymmetric diphosphine coordination best described as κ1. The structures of [(SnCl2)2(μ-Ph2P(CH2)2PPh2)] and of [SnCl{o-C6H4(AsMe2)2}]SnCl3 reveal trigonal pyramidal cores, but with longer Sn⋯Cl bridges affording polymeric structures. The synthesis of [SnCl2(R3EO)2] (R = Ph, E = P or As; and R = Me, E = P) are also reported, along with the structure of [SnCl2(Me3PO)2], which contains distorted tetragonal pyramidal Sn(II) coordination. X-ray structures are also reported for [(PMe3)2CH2][SnCl3]2 and [Ph2P(H)(CH2)2P(H)Ph2][SnCl3]2, obtained as by-products from the attempts to synthesise phosphine complexes, as well as [(o-C6H4(PMe2)2CH2]I2. All complexes were characterised by microanalysis, IR and multinuclear NMR spectroscopy (1H, 19F{1H}, 31P{1H } and, where solubility allowed, 119Sn). Comparisons are drawn with corresponding Sn(IV) and Ge(II) complexes.

Telluroether and Selenoether Complexes as Single Source Reagents for Low Pressure Chemical Vapor Deposition of Crystalline Ga2Te3 and Ga2Se3 Thin Films

Abstract: The neutral complexes [GaCl3(EnBu2)] (E = Se or Te), [(GaCl3)2{nBuE(CH2)nEnBu}] (E = Se, n = 2; E = Te, n = 3), and [(GaCl3)2{tBuTe(CH2)3TetBu}] are conveniently prepared by reaction of GaCl3 with the neutral EnBu2 in a 1:1 ratio or with nBuE(CH2)nEnBu or tBuTe(CH2)3TetBu in a 2:1 ratio and characterized by IR/Raman and multinuclear (1H, 71Ga, 77Se{1H}, and 125Te{1H}) NMR spectroscopy, respectively, all of which indicate distorted tetrahedral coordination at Ga. The tribromide analog, [GaBr3(SenBu2)], was prepared and characterized similarly. A crystal structure determination on [(GaCl3)2{tBuTe(CH2)3TetBu}] confirms this geometry with each pyramidal GaCl3 fragment coordinated to one Te donor atom of the bridging ditelluroether, Ga–Te = 2.6356(13) and 2.6378(14) A. The nBu-substituted ligand complexes serve as convenient and very useful single source precursors for low pressure chemical vapor deposition (LPCVD) of single phase gallium telluride and gallium selenide, Ga2E3, films onto SiO2 and TiN substrate...

Lead(II) tetrafluoroborate and hexafluorophosphate complexes with crown ethers, mixed O/S- and O/Se-donor macrocycles and unusual [BF4]− and [PF6]− coordination

Abstract: The reaction of Pb[BF4]2 in H2O/MeCN solution with the macrocycle 18-crown-6 gave the dinuclear complex [{Pb(18-crown-6)(H2O)(μ2-BF4)}2][BF4]2, containing two nine-coordinate lead centres, each bound to all six oxygens of a crown ligand, one water molecule and bridged by two μ2-BF4 groups. In contrast, the oxa-thia crown [18]aneO4S2 gave the mononuclear [Pb([18]aneO4S2)(H2O)2(BF4)][BF4] in which the lead is coordinated O4S2 within the puckered ring of the macrocycle, and with two water molecules on one side of the plane and a chelating (κ2) BF4− on the other. The [Pb([18]aneO4Se2)(BF4)2] has the two BF4− groups arranged mutually cis and with the macrocycle folded; within each BF4− group the Pb–F distances differ by ∼0.5 A, producing a very unsymmetrical chelate. The 15-membered ring macrocycles 15-crown-5 and [15]aneO3S2 produce sandwich complexes [Pb(macrocycle)2][BF4]2 which contain 10-coordinate lead centres. Pb[PF6]2 in H2O/MeCN solution formed [Pb(18-crown-6)(H2O)2(PF6)][PF6] and [Pb([18]aneO4S2)(H2O)2(PF6)][PF6] which contain weak κ2-coordination of the PF6− group on the opposite side of the macrocyclic ring to two coordinated water molecules, giving 10-coordinate lead. In contrast, [Pb([18]aneO4Se2)(PF6)2] has two κ2-coordinated PF6− groups disposed cis, with a very folded macrocycle conformation. In [Pb(18-crown-6)(NO3)(PF6)] a chelating nitrate group occupies the coordination sites at Pb(II) instead of the two water molecules, and the weakly coordinating PF6− group is tridentate. The crystal structures of the lead nitrate complexes, [Pb(15-crown-5)(NO3)2] and [Pb([18]aneO4Se2)(NO3)2], containing nine- and 10-coordinate lead respectively, are also reported. In solution the complexes are labile, and both conductivity and 19F NMR spectroscopic studies show the BF4− and PF6− groups are dissociated, whereas in the nitrate complexes the anion coordination is retained in solution. The identification of the coordination modes of the NO3− and BF4− groups in the solid complexes by IR spectroscopy is discussed.

Area Selective Growth of Titanium Diselenide Thin Films into Micropatterned Substrates by Low-Pressure Chemical Vapor Deposition.

Abstract: The neutral, distorted octahedral complex [TiCl4(Se n Bu2)2] (1), prepared from the reaction of TiCl4 with the neutral Se n Bu2 in a 1:2 ratio and characterized by IR and multinuclear (1H, 13C{1H}, 77Se{1H}) NMR spectroscopy and microanalysis, serves as an efficient single-source precursor for low-pressure chemical vapor deposition (LPCVD) of titanium diselenide, TiSe2, films onto SiO2 and TiN substrates. X-ray diffraction patterns on the deposited films are consistent with single-phase, hexagonal 1T-TiSe2 (P3m1), with evidence of some preferred orientation of the crystallites in thicker films. The composition and structural morphology was confirmed by scanning electron microscopy (SEM), energy dispersive X-ray, and Raman spectroscopy. SEM imaging shows hexagonal plate crystallites growing perpendicular to the substrate, but these tend to align parallel to the surface when the quantity of reagent is reduced. The resistivity of the crystalline TiSe2 films is 3.36 ± 0.05 × 10-3 Ω·cm with a carrier density of 1 × 1022 cm-3. Very highly selective film growth from the reagent was observed onto photolithographically patterned substrates, with film growth strongly preferred onto the conducting TiN surfaces of SiO2/TiN patterned substrates. TiSe2 is selectively deposited within the smallest 2 μm diameter TiN holes of the patterned TiN/SiO2 substrates. The variation in crystallite size with different diameter holes is determined by microfocus X-ray diffraction and SEM, revealing that the dimensions increase with the hole size, but that the thickness of the crystals stops increasing above ∼20 μm hole size, whereas their lengths/widths continue to increase.

s-Block chalcogenoether chemistry--thio- and selenoether coordination with hard Group 2 ions.

Abstract: A highly unusual series of Group 2 complexes with soft thio- and selenoether coordination, [MI2([18]aneO4E2)] (M = Ca or Sr; E = S or Se), [CaI2([18]aneO2S4)] and [MI2([15]aneO3S2)], has been prepared by reaction of anhydrous MI2 with the macrocycle in dry MeCN solution. The complexes have been characterised via1H NMR and IR spectroscopy, microanalysis and crystallographic studies which provide unambiguous confirmation of the M–S/Se coordination. The neutral complexes are seven- or eight-coordinate with the iodo ligands cis. The long M–E bond distances of ∼3.0 A indicate weak interactions, but they are significantly less than the sum of the van der Waals radii for M and E, and are important in facilitating isolation of the complexes. Trace hydrolysis of [MI2([18]aneO4E2)] and [SrI2([15]aneO3S2)] leads, unexpectedly, to displacement of the iodo ligands rather than the S/Se donor functions, and the resulting dicationic [Ca(H2O)2([18]aneO4S2)]I2, [Sr(H2O)3([18]aneO4S2)]I2·H2O, [Sr(H2O)3([18]aneO4Se2)]I2 and [Sr(H2O)3([15]aneO3S2)]I2 complexes have been structurally characterised, forming eight- and nine-coordinate cations, with all the macrocyclic donor atoms coordinated. Reaction of Ca(CF3SO3)2 with [18]aneO4S2 in anhydrous MeCN solution similarly affords [Ca(CF3SO3)2([18]aneO4S2)], albeit in low yield, also proven crystallographically. Using the MI2 precursors provides a general entry into this area of coordination chemistry of these Group 2 ions, owing in part at least to their higher solubility in the weak donor (weakly competing) MeCN solvent. While CaCl2 reacts with 18-crown-6 either directly in MeCN giving [CaCl2(18-crown-6)], or in the presence of SbCl5 (to form trans-[Ca(MeCN)2(18-crown-6)][SbCl6]2), neither of these routes works with the oxa-thia or oxa-selena crowns.

Trivalent scandium, yttrium and lanthanide complexes with thia-oxa and selena-oxa macrocycles and crown ether coordination

Abstract: Complexes of the oxa-thia macrocycles [18]aneO4S2, [15]aneO3S2 and the oxa-selena macrocycle [18]aneO4Se2 (L) of types [MCl2(L)]FeCl4 (M = Sc or Y) were prepared from [ScCl3(thf)3] or [YCl2(THF)5][YCl4(THF)2] and the ligand in anhydrous MeCN, using FeCl3 as a chloride abstractor. The [MI2(L)]I, [LaI3(L)] and [LuI2(L)]I have been prepared from the ligands and the appropriate anhydrous metal triiodide in MeCN. Complexes of type [LaI3(crown)] and [LuI2(crown)]I (crown = 18-crown-6, 15-crown-5) were made for comparison. Use of the metal iodide results in complexes with high solubility compared to the corresponding chlorides, although also with increased sensitivity to moisture. All complexes were characterised by microanalysis, IR, 1H, 45Sc and 77Se NMR spectroscopy as appropriate. X-ray crystal structures are reported for [ScCl2([18]aneO4S2)][FeCl4], [ScI2([18]aneO4S2)]I, [YCl2(18-crown-6)]3[Y2Cl9], [YCl2([18]aneO4S2)][FeCl4], [LaI3(15-crown-5)], [LaI2(18-crown-6)(MeCN)]I, [LuI(18-crown-6)(MeCN)2]I2, [Lu(15-crown-5)(MeCN)2(OH2)]I3, [LaI3([18]aneO4S2)], [LaI([18]aneO4S2)(OH2)]I2, [LaI3([18]aneO4Se2)] and [LuI2([18]aneO4Se2)]I. In each complex all the neutral donor atoms of the macrocycles are coordinated to the metal centre, showing very rare examples of these oxophilic metal centres coordinated to thioether groups, and the first examples of coordinated selenoether donors. In some cases MeCN or adventitious water displaces halide ligands, but not the S/Se donors from La or Lu complexes. A complex of the oxa-tellura macrocycle [18]aneO4Te2, [ScCl2([18]aneO4Te2)][FeCl4] was isolated, but is unstable in MeCN solution, depositing elemental Te. YCl3 and 18-crown-6 produced [YCl2(18-crown-6)]3[Y2Cl9], the asymmetric unit of which contains two cations with a trans-YCl2 arrangement and a third with a cis-YCl2 group.

Sc(III) complexes with neutral N3- and SNS-donor ligands – a spectroscopic study of the activation of ethene polymerisation catalysts

Abstract: Scandium trichloride complexes with tridentate N3- and S2N-donor ligands (L3) have been synthesised and characterised by IR, 1H, 13C{1H} and 45Sc NMR spectroscopy, microanalysis, and solid state and solution XAFS spectroscopy. Catalytic testing of a subset of these complexes with ethene has been undertaken in chlorobenzene with MMAO-3A and PMAO-IP at 60 °C and 40 bar ethene, giving low activity ethene polymerisation. The reactions of these complexes with MeLi and AlMe3 were studied by 1H, 13C{1H}, 27Al and 45Sc NMR spectroscopy and in situ via Sc K-edge XAFS spectroscopy. Three or four mol. equivalents of MeLi react with [ScCl3(Me3-tacn)] in THF solution to form [ScMe3(Me3-tacn)] cleanly, while complexes of type [ScCl3(R-SNS)] {R-SNS = HN(CH2CH2SC10H21)2} form two different species proposed to be [ScMe3(R-SN(Li)S)] and [ScMe2(R-SN−S)]. In contrast, in situ45Sc NMR and Sc K-edge XAFS spectroscopic studies of the reaction of [ScCl3(Me3-tacn)] with 10 mol. equivalents of AlMe3 strongly suggest that alkylation at the Sc(III) centre does not occur, instead retaining the Cl3N3 coordination environment and most likely forming Sc−Cl−AlMe3 bridging interactions. Similar studies on [ScCl3(decyl-SNS)] with 10 mol. equivalents of AlMe3 are also consistent with this, indicating that alkylation at the Sc centre does not occur except in the presence of co-catalyst [Ph3C][Al{OC(CF3)3}4] and the α-alkene, hex-1-ene.

Oxa-thia-, oxa-selena and crown ether macrocyclic complexes of tin( ii ) tetrafluoroborate and hexafluorophosphate – synthesis, properties and structures

Abstract: The reactions of Sn(BF4)2 and Sn(PF6)2 with crown ethers and oxa-thia- or oxa-selena-macrocycles are complex, with examples of fragmentation of the fluoroanions, and cleavage of the ligands observed, in addition to adduct formation. The reaction of Sn(BF4)2 with 15-crown-5 or 18-crown-6 produced the sandwich complex [Sn(15-crown-5)2][BF4]2 with 10-coordinate tin, and [Sn(18-crown-6)(H2O)][BF4]2·2H2O which has an hexagonal pyramidal tin centre with two long contacts to lattice water molecules (overall 7 + 2 coordination). [Sn(18-crown-6)(PF6)][PF6] is formed from 18-crown-6 and Sn(PF6)2, but the hexafluorophosphate ions hydrolyse readily in these systems to produce F− which coordinates to the tin to produce [Sn(18-crown-6)F][PF6], which can also be made directly from Sn(PF6)2, 18-crown-6 and KF in MeCN. The structure contains a hexagonal pyramidal coordinated Sn(II) cation with an apical fluoride. The oxa-thia macrocycle [18]aneO4S2 forms [Sn([18]aneO4S2)(H2O)2(PF6)][PF6], from which some crystals of composition [Sn([18]aneO4S2)(H2O)2(PF6)]2[PF6][F] were obtained. The cation contains an approximately planar O4S2 coordinated macrocycle, with two coordinated water molecules on one side of the plane and a weakly bound (κ2) PF6− group on the opposite face, and with the fluoride ion hydrogen bonded to the coordinated water molecules. In contrast, the oxa-selena macrocycle, [18]aneO4Se2, produces an anhydrous complex [Sn([18]aneO4Se2)(PF6)2] which probably contains coordinated anions, although it decomposes quite rapidly in solution, depositing elemental Se, and hence crystals for an X-ray study were not obtained. Reacting Sn(BF4)2 and [18]aneO4Se2 or [18]aneO4S2 also causes rapid decomposition, but from the latter reaction crystals of the 1,2-ethanediol complex [Sn([18]aneO4S2){C2H4(OH)2}][BF4]2 were isolated. The structure reveals the coordinated macrocycle and a chelating diol, with the O–H protons of the latter hydrogen bonded to the [BF4]− anions. This is a very rare, structurally authenticated example of ring opening/cleavage of an oxa-thia macrocycle. The new complexes were characterised by microanalysis, IR, 1H, 19F{1H} and 31P{1H} NMR spectroscopy as appropriate, and X-ray structures are reported for [Sn(15-crown-5)2][BF4]3[H3O]·H2O, [Sn(18-crown-6)(H2O)][BF4]2·2H2O, [Sn(18-crown-6)F][PF6], [Sn([18]aneO4S2)(H2O)2(PF6)]2[PF6][F] and [Sn([18]aneO4S2){C2H4(OH)2}][BF4]2. The complexes are compared and contrasted with chloro-tin(II) complexes of crown ethers, germanium(II) and lead(II) analogues.

Phosphine and diphosphine complexes of silicon(IV) halides

Abstract: The reaction of SiX4 (X = Cl or Br) with PMe3 in anhydrous CH2Cl2 forms trans-[SiX4(PMe3)2], while the diphosphines, Me2P(CH2)2PMe2, Et2P(CH2)2PEt2, and o-C6H4(PMe2)2 form cis-[SiX4(diphosphine)], all containing six-coordinate silicon centers. With Me2PCH2PMe2 the product was trans-[SiCl4(κ(1)-Me2PCH2PMe2)2]. The complexes have been characterized by X-ray crystallography, microanalysis, IR, and multinuclear ((1)H, (13)C{(1)H}, and (31)P{(1)H}) NMR spectroscopies. The complexes are stable solids and not significantly dissociated in nondonor solvents, although they are very moisture and oxygen sensitive. This stability conflicts with the predictions of recent density functional theory (DFT) calculations (Wilson et al. Inorg. Chem. 2012, 51, 7657-7668) which suggested six-coordinate silicon phosphines would be unstable, and also contrasts with the failure to isolate complexes with SiF4 (George et al. Dalton Trans. 2011, 40, 1584-1593). No reaction occurred between phosphines and SiI4, or with SiX4 and arsine ligands including AsMe3 and o-C6H4(AsMe2)2. Attempts to make five-coordinate [SiX4(PR3)] using the sterically bulky phosphines, P(t)Bu3, P(i)Pr3, or PCy3 failed, with no apparent reaction occurring, consistent with predictions (Wilson et al. Inorg. Chem. 2012, 51, 7657-7668) that such compounds would be very endothermic, while the large cone angles of the phosphines presumably preclude formation of six-coordination at the small silicon center. The reaction of Si2Cl6 with PMe3 or the diphosphines in CH2Cl2 results in instant disproportionation to the SiCl4 adducts and polychlorosilanes, but from hexane solution very unstable white [Si2Cl6(PMe3)2] and [Si2Cl6(diphosphine)] (diphosphine = Me2P(CH2)2PMe2 or o-C6H4(PMe2)2) precipitate. The reactions of SiHCl3 with PMe3 and Me2P(CH2)2PMe2 also produce the SiCl4 adducts, but using Et2P(CH2)2PEt2, colorless [SiHCl3{Et2P(CH2)2PEt2}] was isolated, which was characterized by an X-ray structure which showed a pseudo-octahedral complex with the Si-H trans to P. Attempts to reduce the silicon(IV) phosphine complexes to silicon(II) were unsuccessful, contrasting with the isolation of stable N-heterocyclic carbene adducts of Si(II).

Thioether coordination to divalent selenium halide acceptors – synthesis, properties and structures

Abstract: The tetravalent SeCl4 and SeBr4 are reduced in the presence of thioether ligands L (SMe2, tht) or L–L (MeS(CH2)nSMe (n = 2 or 3), o-C6H4(SMe)2) in MeCN solution at 0 °C, forming Se(II) thioether complexes, including the crystallographically characterised halo-bridged chain polymers [SeX2(SMe2)] (X = Cl or Br), molecular trans-[SeX2(tht)2], cis-[SeBr2{MeS(CH2)2SMe}] and the thioether-bridged polymer [SeBr2{MeS(CH2)3SMe}], as the main products, together with halogenated ligand. The [SeX2(L)2] and [SeX2(L–L)] complexes are all based upon distorted square planar coordination, with two Se-based lone pairs assumed to occupy the (vacant) axial sites, and Se–S bond distances of ca. 2.4–2.6 A. The 1 : 1 species [SeX2(SMe2)] are T-shaped with trans X groups and weak intermolecular Se⋯X contacts. The SeCl2-thioether complexes are less stable than the bromides, both in solution in CH2Cl2 and as solids at ambient temperature. Reaction of SeBr4 with o-C6H4(SMe2)2 leads to the red complex cis-[SeBr2{κ1-o-C6H4(SMe)2}2] as the major product; together with a minor (yellow) product formed via bromination of the aromatic ring, [SeBr2{4-Br-1,2-(SMe)2-C6H3}2]. The crystal structure confirms a V-shaped SeBr2 unit with long (weak) κ1-interactions to one S donor (meta to the Br) from two brominated ligands – an extremely rare coordination mode for an o-phenylene dithioether. Similar reaction of o-C6H4(SMe2)2 with SeCl4 leads to several species, including monosulfonium cation, [1]+ formed by coupling of one thioether group to the C4-position of the phenylene backbone in an adjacent molecule, confirmed crystallographically. Carbon-sulfur coupling is also evident in the reaction of SeX4 with o-C6H4(CH2SMe)2, leading to two related cyclic sulfonium species, [2]+ and [3]+, which were structurally characterised as [SeBr4]2− and [Se2Cl6]2− salts respectively. Reaction of SeX4 with SeMe2 leads to halogenation of the ligand to form Me2SeX2 and reduction of the SeX4 to elemental selenium.

Chromium(V) Oxide Trichloride, and some Pentachlorido‐­oxido‐chromate(V) Salts: Structures and Spectroscopic ­Characterization

Abstract: Crystalline CrOCl3 contains [Cl2OCr(?-Cl)2CrOCl2] molecules with two square pyramidal CrOCl4 units sharing a common edge and with the Cr–O arranged anti, a new structure type for transition metal MOX3 compounds. Crystals are monoclinic with space group P21/c, Z = 4, with a = 5.735(5), b = 13.738(7), c = 11.318(4) A, ? = 90°, ? = 98.346(6)°, ? = 90°. Its IR and UV/Vis spectra are reported and compared with those of the C3v monomer found in the gas phase. Structures are also reported for M2[CrOCl5] (M = Cs or Rb) and show a pseudo-octahedral anion. Cs2[CrOCl5] adopts a K2PtCl6-type structure with [CrOCl5]2– ions randomly orientated, but Rb2[CrOCl5] is orthorhombic with space group Pnma with a = 13.6471(7), b = 9.9175(5), and c = 6.9562(4) A. Rietveld refinement of the data on the rubidium salt gave Cr–O = 1.628(1), Cr–CltransO = 2.652(7), Cr–CltransCl = 2.239(8)–2.342(3) A. Corresponding CrV oxide bromide species do not form

Tribenzylphosphane and its hydrochloride salt, tribenzylphosphonium hydrogen dichloride-tribenzylphosphane (1/1).

Abstract: Tri­benzyl­phosphane, PBz3 (C21H21P), crystallizes in a notably different unit cell to its Group 15 analogues NBz3 and SbBz3. The packing is dominated by face–edge π-inter­actions which result in infinite columns of mol­ecules parallel to the b axis; these columns are linked by further face–edge π-inter­actions into sheets of columns parallel to the [101] direction. Its hydro­chloride salt, tri­benzyl­phospho­nium hydrogen di­chlo­ride–tri­benzyl­phosphane (1/1), lies on a threefold axis within a trigonal crystal system. It exists in the solid state as a hydrogen-bridged dimer with the composition [H(PBz3)2]+[HCl2]− (C42H43P2+·HCl2−). The cation is the first structurally authenticated example of a phosphane acting as a hydrogen-bond acceptor to a phospho­nium group and the cations are linked into a three-dimensional network through inter­molecular face–edge π-inter­actions.

Acyclic Arsine, Stibine, and Bismuthine Ligands

Abstract: The key features of arsines, stibines and bismuthines as ligands towards transition metal and main group metal/metalloids are described. Following a brief review of the development of the chemistry, the main synthetic routes to the ligands are described and the advantages and limitations of the various approaches outlined. Current views of the nature of the metal-ligand bonding are evaluated, and the main coordination modes of the ligands described with illustrative examples.

Macrocyclic Phosphine and Arsine Ligands

Abstract: The main synthetic routes to phosphine and arsine macrocycles are described. These include high dilution and template directed routes, and the advantages and disadvantages of these methods are discussed. Syntheses are also described for a selection of mixed donor macrocycles containing P or As donors.

Medium and High Oxidation State Metal/Non-Metal Fluoride and Oxide—Fluoride Complexes with Neutral Donor Ligands

Abstract: While most high and medium oxidation state (O.S. ≥ 3) metal and non-metal fluorides and oxide fluorides are strong Lewis acids, exploration of their coordination chemistry with neutral ligands has been limited and mostly non-systematic. This is despite the very different properties conferred on the acceptor centre by the small electronegative fluoride ligands compared to the heavier halides. This article sets out these key differences, discusses possible synthetic routes, the key characterisation techniques, and appropriate bonding models. Current knowledge of the coordination chemistry of d, f and p-block fluorides and oxide fluorides with neutral ligands (with donor atoms drawn from Groups 15 and 16 and including N-heterocyclic carbenes) is then presented and discussed, and the differences in properties compared to complexes containing the heavier halides are illustrated. The emphasis is on work published post 1990, but earlier work is also included as essential background and where no more recent information exists. Attention is drawn to unexplored areas meriting investigation and to possible applications of these complexes.

1.17 – Acyclic Thio-, Seleno-, and Telluroether Ligands

Abstract: The key features of thioethers, selenoethers and telluroethers as ligands towards transition metal and main group metal/metalloids are described. The main synthetic routes to the ligands are described and the advantages and limitations of the various approaches outlined. Current views of the nature of the metal-ligand bonding are evaluated, and the main coordination modes of the ligands described with illustrative examples.

A novel top-down fabrication process for Ge 2 Sb 2 Te 5 phase change material nanowires

Abstract: A novel e-beam free, top-down spacer etch process was used to fabricate sub-hundred nanometer Ge2Sb2Te5 phase change nanowires. Naowires with a cross-section dimension of 50 nm × 100 nm (width × height) were obtained and phase change functionality demonstrated.

An alkyltelluroether precursor for use in the single source chemical vapour deposition of a metal telluride

Abstract: An alkyltelluroether precursor for use in the single source chemical vapour deposition of a metal telluride, which alkyltelluroether precursor comprises an alkyltelluroether ligand bonded to a metal halide, which alkyltelluroether precursor comprises at least one alkyl group containing at least two carbon atoms, and which alkyltelluroether precursor has the general formula: MX n (alkyltelluroether)y where M = metal X = a halide n = 3 or 4, and y = 1, 2 or 3 alkyl = butyl, propyl, ethyl, trimethylsilyl, cyclohexyl, cyclopentyl or benzyl.

Chromium(V) Oxide Trichloride, and Some Pentachlorido-oxido-chromate(V) Salts: Structures and Spectroscopic Characterization.

Abstract: Crystalline CrOCl3 contains [Cl2OCr(?-Cl)2CrOCl2] molecules with two square pyramidal CrOCl4 units sharing a common edge and with the Cr–O arranged anti, a new structure type for transition metal MOX3 compounds. Crystals are monoclinic with space group P21/c, Z = 4, with a = 5.735(5), b = 13.738(7), c = 11.318(4) A, ? = 90°, ? = 98.346(6)°, ? = 90°. Its IR and UV/Vis spectra are reported and compared with those of the C3v monomer found in the gas phase. Structures are also reported for M2[CrOCl5] (M = Cs or Rb) and show a pseudo-octahedral anion. Cs2[CrOCl5] adopts a K2PtCl6-type structure with [CrOCl5]2– ions randomly orientated, but Rb2[CrOCl5] is orthorhombic with space group Pnma with a = 13.6471(7), b = 9.9175(5), and c = 6.9562(4) A. Rietveld refinement of the data on the rubidium salt gave Cr–O = 1.628(1), Cr–CltransO = 2.652(7), Cr–CltransCl = 2.239(8)–2.342(3) A. Corresponding CrV oxide bromide species do not form

Selective deposition of phase change materials by chemical vapor deposition and electrodeposition

Abstract: We report selective deposition methods for phase change materials by chemical vapor deposition (CVD) and electrodepostion. Firstly, high selective deposition of SnSe2 and Bi2Te3 films on TiN is observed in low pressure CVD on photolithographically patterned SiO2/TiN substrates by single source precursors. Secondly, a non-aqueous electrochemical system for the electrodeposition of high-purity elemental Bi, Sb, Se and Te is described. This system enables the deposition of binary and ternary phase change materials. The deposition and characterization of Sb 2Te3 by this system is presented.