Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6.
Inorg Chem. 2010 Feb 15;49(4):1976-82. doi: 10.1021/ic902411h.
A family of new mixed-ligand titanium guanidinate compounds was synthesized as potential atomic layer deposition precursors, and the surface chemistry on silica of a promising candidate (Cp(2)Ti[(N(i)Pr)(2)CN(H)(i)Pr]) was explored. Generally, these compounds have very good thermal stability with onsets of volatility between 127 and 168 degrees C, with melting points generally ranging from 147 to 165 degrees C. The reactivity of [(i)PrN(H)C(N(i)Pr)(2)]TiCp(2) was studied with high surface area silica between 180 and 330 degrees C. The surface reactivity was found to differ if the silica was preheated to 350 or 900 degrees C; this was attributed to the hydroxyl nucleation site density of the silica, which is known to vary with the temperature. The surface reaction products were characterized by solid-state NMR, and these agreed well with a calculated model. When the silica was pretreated to 350 degrees C, the precursor appeared to chemisorb primarily through the loss of a Cp ligand, while with a 900 degrees C pretreatment, the chemisorption occurred primarily through a loss of the guanidinate ligand. The adsorption enthalpies to silica were calculated for the different surface species.
作为潜在原子层沉积前体，合成了一系列新型混合配体钛胍化合物，并研究了有前途的候选物（Cp(2)Ti[(N(i)Pr)(2)CN(H)(i)Pr]）在二氧化硅表面上的化学性质。通常，这些化合物具有非常好的热稳定性，起始挥发性在 127 和 168 摄氏度之间，熔点通常在 147 和 165 摄氏度之间。在 180 和 330 摄氏度之间研究了[(i)PrN(H)C(N(i)Pr)(2)]TiCp(2)与高表面积二氧化硅的反应性。发现如果二氧化硅预先加热到 350 或 900 摄氏度，表面反应性会有所不同；这归因于二氧化硅的羟基成核位点密度，众所周知，其随温度而变化。通过固态 NMR 对表面反应产物进行了表征，这些产物与计算模型吻合得很好。当二氧化硅预处理至 350 摄氏度时，前体似乎主要通过失去 Cp 配体进行化学吸附，而在 900 摄氏度预处理时，化学吸附主要通过失去胍配体发生。计算了不同表面物种在二氧化硅上的吸附焓。
