In the organometallic chemistry, the imido complexes are an interesting species because it of their rich reactivity. Imido has two forms, where M=N-R form is nucleophilic and M¡ÝN-R form is elctrophilic. The
thermo- or photochemical- decomposition of metal azido complexes is known to result in the formation of the corresponding metal nitride(M¡ÝN) or imido complexes. These reactions are oxidative cleavage type. As far as we know, imido species have not been generated on metal surfaces; therefore, we attempt to use the azidotrimethylsilane((CH3)3Si-N3 ; TMSN3) as precursors to produce imido species(TMSN=Cu) by N2 extrusion mechanism on Cu(111). The process was explored by a combination of temperature-programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), and X-ray photoemission spectroscopy (XPS) techniques. In addition, density functional theory (DFT) calculations were conducted to obtain the optimized geometries
for the various surface intermediates. The computed IR spectra facilitated the vibrational mode assignments. TPD spectra show that TMSN=Cu was
hydrogenated to the TMSNH2 amine product around 520 K. We propose that the hydrogen source is adsorbed methyl groups, invoking the cleavage of the Si-C bond. TMSCH2N3 molecule was also investigated. In this case, N2 and H2 molecules were found to desorb around 260 K and 320K. A novel TMSC¡ÝN product was observed around 280K. We
suggest it is a result of the metathesis reaction from ethylidyne (TMSC¡ÝCu) and nitride(N¡ÝCu) species. The TMSC¡ÝCu species are produced by double £\-hydride elimination of TMSCH2-Cu groups. The
N¡ÝCu may be generated by the thermaldecomposition of copper azide(N=N=N-Cu). RAIRS reveal that there are three kinds of azido vibrations,where the higher frequency is assigned to the N=N=N-Cu species. This product is verified by the TPD of adsorbed TMSC¡ÝN molecule. Intriguingly, the thermal chemistry of TMSC¡ÝN molecule indicates that
the isomeric molecule TMSN¡ÝC could be formed around 210 K, evidenced by a notable change in the RAIRS. The higher frequency £hC¡ÝN of TMSC¡ÝN transforms into a lower frequency £hC¡ÝN for TMSN¡ÝC. The coverage-dependent studies of RAIRS and XPS performed at 160 K surface temperature show that the isomerization may be intermolecular. The back-£k bonded TMSN¡ÝC molecule is desorbed
around 410 K. XPS and RAIRS at 800 K show that isocyanide could polymerize to polyisocyanide, with an imine structure, and the characteristic C¡ÝN stretching mode disappeared.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0723109-193539 |
| Date | 23 July 2009 |
| Creators | Yu, Pao-tao |
| Contributors | Lan-Chang Liang, Chao-Ming Chiang, Chao-Ming Chiang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0723109-193539 |
| Rights | not_available, Copyright information available at source archive |
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