David A. Rice

The donor properties of simple ethers—II[1]: Complexes of manganese(II), iron(II), cobalt(II) and nickel(II) halides with tetrahydrofuran and 1,2-dimethoxyethane

Abstract The reactions of several dihalides of manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and cadmium(II), and iron(III) chloride with tetrahydrofuran and 1,2-dimethoxyethane have been investigated and the following complexes prepared: MCl 2 ,1·5C 4 H 8 O (M  Mn, Fe or Co), CoX 2 ,C 4 H 8 O (X  Br or I), NiCl 2 ,C 4 H 8 O,C 2 H 5 OH, MX 2 ,C 4 H 10 O 2 (M  Mn, Fe, Co, Ni or Cd and X  Cl, Br or I), FeCl 3 ,C 4 H 10 O 2 and 2CuCl 2 ,C 4 H 10 O 2 . The structures of several of these complexes have been deduced from a study of their electronic spectra, far-i.r. spectra and room-temperature magnetic properties. However, the magnetic moments of several of these complexes (e.g. pseudotetrahedral CoX 2 ,C 4 H 10 O 2 ) are unusual in that they exhibit marked temperature dependence, although the ground state formally is an orbital singlet. The tetrahydrofuran derivatives MCl 2 ,1·5C 4 H 8 O are of unusual stoichiometry, and while it is suggested that these products are a 1:1 mixture of tetrahedral CoCl 2 ,2C 4 H 8 O and octahedral CoCl 2 ,C 4 H 8 O their structure remains in some doubt.

Organometallic precursors to the formation of GaN by MOCVD: structural characterisation of Me3Ga · NH3 by gas-phase electron diffraction

Abstract The molecular structure of Me3Ga · NH3 [I] has been studied by gas-phase electron diffraction at 25°C. The experimental data are fitted by a model in which the C3GaN core of the molecule has C3v symmetry. The molecule was defined in terms of four bond distances, three valence angles and two torsion angles. Of the bond distances three were refined (rg(GaN) = 2.161(22)°, rg(GaC) = 1.979(3) A, rg(CH) = 1.109(7) A). It was necessary to hold the fourth bond distance at an assumed value [rg(NH) = 1.045 A]. Two of the valence angles were refined (NGaC = 101.8(62)°, GaCH = 111.3(16)°) with the third (GaNH) being held at 109.0°. The torsion angle HN / GaC was held at 60.0° while the remaining torsion angle HC / GaN was refined to 37.5(224)°. The dependent angle CGaC was 115.9(42)°, so the C3Ga fragment is not far from planar, which is in accord with the lone pair from the nitrogen atom being donated into the pz orbital on the gallium atom. This suggestion is supported by the gas-phase and low temperature infra-red spectroscopic data that are reported. Evidence is also presented suggesting the GaN bond is weak and thus it is not surprising that when NH3 and Me3Ga are used to grow GaN it is necessary to use NH3 / Me3Ga ratios greater than one.

Novel low-temperature route to known (MnS and FeS2) and new (CrS3, MoS4 and WS5) transition-metal sulfides

The reaction of the transition-metal carbonyls, Mn2(CO)10, Fe(CO)5 or M(CO)6(M = Cr, Mo or W) with sulfur in 1, 2-dichlorobenzene yields polycrystalline MnS (alabandite), FeS2(marcarsite), and three new amorphous sulfur-rich sulfides CrS3, MoS4 and WS5.

A single crystal x-ray diffraction study of yttrium tartrate hydrate [Y(C4H4O6)(C6H5O6) ·2.5H2O]

Abstract Yttrium tartrate hydrate [Y(C4H4O4)(C4H5O6) · 2.5H2O] (A) has been prepared by the reaction of YC13 with tartaric acid in alkaline solution. It is believed that the two tartrate anions, while crystallographically equivalent, have different charges, one being -1 and the other -2. In A the yttrium centre is coordinated to nine oxygen atoms. These nine oxygen atoms originate from four tartrate ligands which are crystallographically identical and from three water molecules, one of which has an occupancy factor of 50%. The metal takes part in two symmetry-related, five-membered chelate rings formed by carboxyl and α-hydroxyl groups from each of two tartrate ligands. The carboxyl groups also form bidentate bridges linking two metal centres. The tartrate groups thus interconnect to give a three-dimensional layered structure to the compound. The coordination at each yttrium centre is completed by three water molecules, one of which is unique. The Y—O distances in the five-membered rings are 2.324(14) (carboxyl oxygen) and 2.489(11)(hydroxyl oxygen). The results of studies utilizing elemental analysis, powder X-ray diffraction and IR spectroscopy support the single crystal diffraction findings. Copyright

The Raman spectra of metal halide complexes containing 1,4-dioxan

Abstract The solid-state Raman spectra of several 1:1 and 1:2 adducts of 1,4-dioxan with manganese(II), iron(II), nickel(II), zinc(II) and mercury(II) halides and the species FeCl 3 , C 4 H 8 O 2 and 3CuCl 2 , 2C 4 H 8 O 2 have been recorded using laser excitation. The absence of infrared-Raman coincidences can be interpreted in terms of the presence of bridging centrosymmetric 1,4-dioxan molecules in the “chair” conformation. The low frequency Raman spectra are also discussed and in several instances give further information on the structures of the complexes.

Reactions of metal dialkyl dithiophosphates part IV. The crystal structure of [Ag{S2P(OEt)2}2]22− a silver anion containing monodentate and tridentate dialkyl dithiophosphate groups

Abstract The reaction between Ag{(S2P(OEt)2} and [Me4N] [S2P(OEt)2] yields [Me4N] [Ag{S2P(OEt)2}2] (1), crystals of which are monoclinic, space group P21/c, with a = 12.966(11), b = 16.159(14), c = 12.898(15) A, β = 106.0(1)°, Z = 2; 2545 significant reflections were measured on a diffractometer and the structure was refined to R = 0.068 (Rw = 0.088). 1 contains the centrosymmetric species [Ag{S2P(OEt)2}2]22− in which two dialkyldithiophosphate ligands bridge the two metal centres while the other two dialkyldithiophosphate residues are monodenrate. The two sulphur atoms of the bridging dialkyldithiophosphate ligands bond very differently; thus while S(1) bridges two silver atoms [2.679(3) and 2.868(3) A], S(2) is only bonded to one metal atom [2.728(3) A]. Thus the ligands in the ring act simultaneously as bridging and chelating ligands. The four coordinate geometry around the metal is completed by S(3) [AgS(3) 2.517(3) A] which is from the monodentate ligand.

Chemical vapour deposition: a matrix isolation study of precursor compounds and reaction intermediates in the formation of cadmium telluride and gallium nitride

Abstract Infrared spectra for the matrix-isolated species R2Te, R2Cd (R=Me or Et), Me3N·GaH3, Me3N·GaMe3 and Me2NH·GaMe3 are reported for the first time. Evidence is also presented for the formation of the weakly bound adducts Me2Cd·(TeEt2)x and Et2Cd·(TeMe2)tx (x = 1 or 2) in a gaseous mixture before trapping in Ar matrices at 14 K. The strength of bonding in Et2Cd·(TeMe2)x is similar to that in the adduct Et2Cd·(SEt2)x and it has a non-linear CCdC unit. Thermal decomposition (60°C) of gaseous Me3N·GaH3 in a glass tube yields Me3N and a Ga mirror — an observation which suggests that the primary step of the reaction is GaN bond rupture. By contrast, the two gaseous adducts Me3N·GaMe3 and Me2NH·GaMe3 decompose thermally and photochemically to yield inter alia methane, a result which implies that the GaN bond remains intact in the primary decomposition step.

Some coordination compounds of zirconium tetrabenzyl and some reactions in which there is insertion into carbonzirconium bonds

Abstract Zirconium tetrabenzyl (ZrBz 4 ) has been allowed to react with a number of nitrogen and oxygen donor ligands. Air-sensitive complexes of formula ZrBz 4 ·2L ZrBz 4 ·L or 2ZrBz 4 ·L have been isolated and characterised by analysis and by NMR and IR spectroscopy. The reaction of ZrBz 4 with SO 2 , PhNCO and MeNCS gave ZrBz(SO 2 Bz) 3 , Zr[NPhC(O)Bz] 4 and Zr(NMeC(S)Bz) 4 respectively.

The adduct formed between dimethylcadmium and 1,4-dioxane, 1,4-dioxanedimethylcadmium(II): a crystallographic and spectroscopic study

Abstract The reaction of dimethylcadmium with 1,4-dioxane gives a 1:1 adduct, 1 . Recently it has been shown that the growth of CdS by metal organic chemical vapour deposition (MOCVD) is improved if the commonly used dimethylcadmium is replaced by 1 . The nature of 1 in the solid state was unknown and so a sample of 1 was sublimed in vacuo to give colourless crystals, on which an X-ray diffraction study was carried out. The cadmium atom is four coordinate, being bound to two methl groups (CdC 2.09(2) A) and two oxygen atoms (CdO(1) 2.88(2) A, CdO(4*) 2.75(2) A) from different 1,4-dioxane molecules, giving rise to an unusual one-dimensional polymeric structure. Evidence for an association between dimethylcadmium and 1,4-dioxane in benzene solution was obtained from a spectroscopic study. 1 is not transported in the gas-phase in sizeable quantities, thus casting doubt upon the role conventionally assigned to it in reducing side reactions in MOCVD.

Carbonyl sulfide (OCS) as a sulfur-containing precursor in MOCVD: a study of mixtures of Me2Cd and OCS in the gas and solid phases and their use in MOCVD

Mixtures of dimethylcadmium (Me2Cd) and carbonyl sulfide (OCS) have been examined in the gas and solid phases over a wide range of temperatures. No interaction is observed between Me2Cd and OCS in a 1:1 molar ratio at room temperature in the gas phase, nor is any interaction detected in the solid phase at liquid-nitrogen temperature. On heating the 1:1 mixtures of Me2Cd and OCS to 250 °C in a sealed vessel, gaseous products are formed. These consist of methane, carbon monoxide and ethane in an approximately 12:2:1 molar ratio, although a large excess of unreacted OCS is also present showing that this compound does not react fully with Me2Cd at 250 °C. In a flow system at 300 °C only methane and carbon monoxide are formed, in the molar ratio 6:1, although the amount of reaction of the OCS is much less (as evidenced by a higher proportion of unreacted OCS). When the flow reaction is repeated at 450 °C more of the OCS reacts and the proportion of carbon monoxide in the gaseous reaction products is much higher. Using a commercial MOCVD apparatus, high-quality layers of cadmium sulfide are obtained from Me2Cd–OCS mixtures. Temperatures in the range 350–450 °C lead to somewhat slow growth rates which only reach 1 µm h–1 when a 200-fold molar excess of OCS over Me2Cd is used. A small amount of prereaction is observed, but only when H2 is used as the carrier gas. This is attributed to the formation of very small concentrations of H2S by reaction of OCS with H2. The resulting epitaxial layers have good thickness and electrical uniformity. These experiments confirm that OCS may be used as a precursor for the growth of thin layers of CdS by MOCVD. However, the large excess of OCS required here suggests that the compound might be more useful for doping than for the growth of pure layers of CdS.