The titanium coordination compound tris(2,2'-bipyridine)titanium Ti(bipy)3, (chemical formula (C10H8N2)3Ti ) was prepared by the reaction of TiCl3 or TiCl4 with three eq. of 2,2’-bipiridine (bipy) and excess of Li metal in THF. Elemental analysis, 1H and 13C NMR spectroscopy was used to check the purity of Ti(bipy) 3. The proton NMR spectrum for Ti(bipy) 3 is consistent with those previously reported. [[i]]
Ti(bipy)3 was reported to be useful for forming amorphous films of TiC by MOCVD. The reason for choosing Ti(bipy)3 is that its molecules dissociate at relatively low temperatures, 200-500°C compared to 1100 to 1350°C required for the conventional crystalline TiC-producing CVD process utilising TiCl4, CH4 and H2.
[i]G.B. Nikiforov, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt, Polyhedron, 2004, Vol.23, Iss. 4, p.561-566 “Reactivity of Ti(bipy)3 and preparation of the Li(THF)4[Al(bipy)2] complex with the dinegative bipy ligand”, https://www.sciencedirect.com/science/article/pii/S0277538703006284
Tris(2,2’-bipyridine) titanium (0) was tested as precursor for the growth of thin films of Ti metal
by low pressure CVD at <600°C temperatures. At a pressure of 1×10−5 Torr, the pyrolysis takes place at 370 °C. Between this temperature and 520 °C, the films obtained
are amorphous. Ti-rich amorphous corrosion resistant layers containing C, N, H impurities were obtained. The ratios C/N and C/H similar to those in the 2,2’-bipyridine ligand
were observed. Presence of organic compounds was detected by SIMS. Byproducts of precursor decomposition were identified by mass spectrometry. The deposited Ti(C,N,H) layers demonstrated lack of reactivity in acid media such as HF and H2SO4. High corrosion resistance of the coatings was studied by investigating their electrochemical behavior in various acid media (5N H2SO4, 6N HCl, 1N HBr) and compared with those of Ti, TiC, TiN. Similar behavior of the deposits to TiC was
observed; the corrosion resistance of the grown layers can be explained either by their amorphous structure, or by the presence of organic molecules. The amorphous state of Ti(bipy)3-deposited Ti(C,N,H) films persisted
even at 1000°C, what was explained by a dissociative adsorption of the 2,2’-bipyridine molecule during decomposition of [Ti(bipy)3]. [i], [ii]
[i] Morancho, R., Petit, J., Dabosi, F., and Constant, G., “A Corrosion Resistant Titanium Rich Deposit Prepared by CVD at Low Temperature from Tris-(2.2’Bipyridine) Titanium,” Proc. 7th Int. Conf. on CVD, (T. O. Sedgwick and H. Lydtin, eds.), pp. 593–603, Electrochem. Soc., Pennington, NJ 08534 (1979)
[ii] R. Morancho, G. Constant, J.J. Ehrhardt, Thin Solid Films, 1981, Vol.77, Iss. 1–3, p. 155-164, « Ti(C, N, H) coatings on glass substrates prepared by chemical vapour deposition using tris(2,2′-bipyridine)titanium(0) », doi.org/10.1016/0040-6090(81)90372-2, www.sciencedirect.com/science/article/pii/0040609081903722
Ti(bipy)3 was applied as precursor for the growth of amorphous titanium carbide (TiC) thin films by MOCVD at 520°C and at <500°C. The structure of deposited layers ranged from microcrystalline to amorphous, according to X-ray and electron diffraction studies. The grown TiC layers were analyzed by SIMS, AES and ESCA. Potentiodynamic studies of MOCVD grown amorphous TiC layers were perfromed to study the influence of organic clusters trapped in the layers on their corrosion resistance; the results were compared to evaporated amorphous TiC coatings and bulk polycrystalline TiC. The principal corrosion product in the anodic region is believed to be TiOx in all cases, however individual differences were observed in the potentiodynamic plots, especially in the cathodic region, with very little net current observed for the MOCVD-obtained TiC layers, until their breakdown at low potentials. The peak observed at -0.7V (SCE) could correspond to a reduction reaction in which Ti(IV) might transform to Ti(III). The generally higher corrosion resistance of the Ti(bipy)3-MOCVD-deposited TiC coatings was attributed primarily to the presence of organic molecules in the film and only secondarily to their amorphous structure.[i],[ii], [iii]
[i] C.M. Alloca, W.S. Williams, A.E. Kaloyeros, J. Electrochem. Soc., 1987, Vol.134, Iss.12, 3170-3175, doi: 10.1149/1.2100364, http://jes.ecsdl.org/content/134/12/3170.short, « Electrochemical Characteristics of Amorphous Titanium Carbide Films Produced by Low‐Temperature Metal‐Organic Chemical Vapor Deposition (MOCVD) », http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.861.9914&rep=rep1&type=pdf
[ii] A. Kaloyeros, M. Hoffman, W.S. Williams, Thin Solid Films, 1986, Vol.141, Iss.2, p. 237-250, « Amorphous transition metal carbides », https://doi.org/10.1016/0040-6090(86)90352-4, https://www.sciencedirect.com/science/article/pii/0040609086903524
[iii] A. Kaloyeros, W. S. Williams, Applied Physics A, 1987, Volume 42, Issue 2, pp 139–143, « Application of molecular (static) secondary ion mass spectroscopy to detection of organic molecules in amorphous titanium carbide »,link.springer.com/article/10.1007/BF00616724