| Abstract
| - The reaction between LiN(SiMe3)2 and Co(N(SiMe3)2)2 followed by the additon of an aryl alcohol (HOAr) yielded Li2Co(OAr)4(solv)x. Thin films of the spinel phase of LiCoO2 were formed by spin-cast deposition methods using 5 or 6 [OAr = oMP (5), oPP (6); solv = py]. Cyclic voltammetry (shown) revealed two irreversible oxidation processes followed by one reversible process, the latter of which is found to occur at about 4.2 V.
- The reaction between LiN(SiMe3)2 and Co(N(SiMe3)2)2 in THF followed by the addition ofan aryl alcohol (HOAr) yielded: [Co[(μ-OAr)2Li(THF)x]2 [where x = 2: OAr =: OC6H4Me-2(oMP, 1), OC6H4(OCHMe2)-2 (oPP, 2), OC6H3(Me)2-2,6 (DMP, 3); where x = 1: OAr = OC6H3(OCHMe2)2-2,6 (DIP, 4)]. Undertaking the same synthesis in pyridine (py) led to the samegeneral structure with py molecules substituted for the THF solvent molecules: [Co[(μ-OAr)2Li(py)2]2 (OAr = oMP (5), oPP (6)]. For 1−6, the tetrahedrally (Td) bound Co atombridges two OAr ligands to each of the Li atoms. The Li atom adopts a Td or trigonalbipyramidal (TBP) geometry, as determined by the number of bound solvent molecules. Forthe more sterically demanding ligands with py as the solvent, the mononuclear monometallicspecies [Co[(μ-OAr)2(py)x]2 (OAr = DMP (7), x = 2; DIP (8), x = 3) were observed adoptinga Td or TBP geometry, respectively, based on the number of bound solvent molecules.Increasing the steric bulk of the OAr to OC6H3But2-2,6 (DBP) in either THF or py led to theisolation of the previously characterized [Li(DBP)(solv)]2. Calculated XRD powder patternswere generated from the single-crystal structure of 1−8 and used to verify the identity ofthe bulk powder. Attempts to use these compounds for MOCVD applications were notsuccessful due to low volatility of these compounds. Attempts to generate nanoparticles ofthe spinel phase of LiCoO2 by injecting a py solution of 5 or 6 into boiling methyl-imidazole(MeIm)/H2O 95:5) led to nanoparticles of Co(OH)2 only, as characterized by XRD and TEM.Thin films of the spinel phase of LiCoO2 were formed by spin-cast deposition methods using5 or 6 dissolved in a py/toluene mixture onto platinized silicon wafers followed by firing at700 °C. Cyclic voltammetry revealed two irreversible oxidation processes followed by onereversible process, the latter of which is found to occur at about 4.2 V. XRD analysis of thethin film, both before and after electrochemical cycling, revealed only minimal variations inthe crystal structure of the film after cycling. This family of compounds, even thoughstoichiometrically incorrect, have been shown to be useful for single-source applications inthe solid and liquid techniques.
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