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Title:Transition metal allyls and hydrides as chemical vapor deposition precursors
Author(s):Gozum, John Ekrem
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Physics, Electricity and Magnetism
Engineering, Materials Science
Abstract:Thin films of high purity palladium can be prepared at low temperature (250$\sp\circ$C) metal-organic chemical vapor deposition of bis(allyl)palladium or (cyclopentadienyl)(allyl)palladium.
Metal sulfide films may be deposited from the precursors $\rm Fe\sb2S\sb2(CO)\sb6$ and Ti(S-t-Bu)$\sb4$ to give thin films of iron sulfide and titanium disulfide at low temperature.
CVD of Ti(BH$\sb4)\sb3$(dme) at 200$\sp\circ$C resulted in deposition of thin films of TiB$\sb2$. The AES data establish the films as TiB$\sb{2.07}$ with less than 5% carbon and oxygen in the film interior.
Passage of Zr(BH$\sb4)\sb4$ or Hf(BH$\sb4)\sb4$ through a hot zone at 250$\sp\circ$C resulted in deposition of thin films of MB$\sb2$.
In order to trap some of the hydride species that may be formed from the CVD of Zr(BH$\sb4)\sb4$ and Hf(BH$\sb4)\sb4$, these precursors were thermolyzed in the presence of small alkyl phosphines. Treatment of the zirconium and hafnium tetrahydroborate complexes M(BH$\sb4)\sb4$ with trimethylphosphine yields crystals of the new polyhydride $\rm Zr\sb2H\sb3(BH\sb4)\sb5(PMe\sb3)\sb2$ and $\rm Hf\sb2H\sb3(BH\sb4)\sb5(PMe\sb3)\sb2$. Single crystal X-ray diffraction studies of the complexes reveal a distinctly asymmetric dinuclear structure bridged by three hydrogen atoms.
Treatment of $\rm Zr(BH\sb4)\sb4$ or $\rm Hf(BH\sb4)\sb4$ with trimethylphosphine for extended reaction times has given two new polyhydrides of stoichiometry $\rm M\sb3H\sb6(BH\sb4)\sb6(PMe\sb3)\sb4$. The variable temperature $\sp1$H, $\sp{31}$P, and $\sp{11}$B NMR data suggest that these trinuclear compounds contain a non-cyclic M($\mu$-H)$\sb3$M($\mu$-H)$\sb3$M backbone with the phosphine and tetrahydroborate ligands distributed in 2:2:0 and 2:1:3 ratios among the three metal centers. This suggestion has been confirmed by a single crystal X-ray structure.
Treatment of the M(BH$\sb4)\sb4$ complexes with the bidentate phosphine 1,2-bis(dimethyl-phosphino)ethane (dmpe) gives mononuclear hydrides of stoichiometry MH(BH$\sb4)\sb3$(dmpe)$\sb2$ or $\rm MH\sb2(BH\sb4)\sb2(dmpe)\sb2$ depending on the conditions.
Treatment of the polyhydride complexes $\rm M\sb2H\sb3(BH\sb4)\sb5(PMe\sb3)\sb2$ with dmpe has given two new group 4 polyhydrides of stoichiometry $\rm M\sb2H\sb4(BH\sb4)\sb4(dmpe)\sb2$. The variable temperature NMR data suggest that these dinuclear compounds contain a M($\mu$-H)$\sb3$M backbone with the phosphine and tetrahydroborate ligands distributed in 2:0 and 1:3 ratios among the two metal centers; this has been confirmed by the single crystal X-ray structure. A terminal hydride is positioned in between the two bidentate dmpe ligands. A dynamic process exchanges these hydride environments, and a likely mechanism for this process has been proposed.
Issue Date:1991
Rights Information:Copyright 1991 Gozum, John Ekrem
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9136603
OCLC Identifier:(UMI)AAI9136603

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