Coordination of Two N2 Molecules to One Ni+ Site in Ni鈥揨SM-5: An FTIR Spectroscopy Study
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- 作者：Videlina Zdravkova ; Mihail Mihaylov ; Konstantin Hadjiivanov
- 刊名：The Journal of Physical Chemistry C
- 出版年：2012
- 出版时间：June 14, 2012
- 年：2012
- 卷：116
- 期：23
- 页码：12706-12711
- 全文大小：343K
- 年卷期：v.116,no.23(June 14, 2012)
- ISSN：1932-7455
文摘
Ni+ cations were produced in a Ni鈥揨SM-5 zeolite by partial reduction with CO, and the ability of the Ni+ and Ni2+ sites to coordinate 14N2, 15N2, and/or CO molecules was studied by FTIR spectroscopy. With Ni+ cations, CO produces mono-, di-, and tricarbonyl species while only mono- and dicarbonyls are formed with Ni2+. Adsorption of 14N2 at 100 K results in formation of Ni2+鈥?sup>14N2 adducts (band at 2343 cm鈥?) and geminal Ni+(14N2)2 complexes (谓s at 2287 and 谓as at 2270 cm鈥?). The Ni+(14N2)2 complexes lose their ligands stepwise during evacuation at 100 K, and two kinds of monoligand Ni+鈥?sup>14N2 species are formed (2252 and 2238 cm鈥?). After 15N2 adsorption, the Ni+(15N2)2 complexes were observed at 2211 and 2194 cm鈥?: the two Ni+鈥?sup>15N2 species at 2178 and 2163 cm鈥?, and the Ni2+鈥?sup>15N2 adducts at 2264 cm鈥?. To prove the geminal structure, coadsorption of 14N2 and 15N2 was studied. It resulted in formation of Ni+(14N2)(15N2) species that were characterized by 14N鈥?sup>14N and 15N鈥?sup>15N stretchings at 2277 and 2201 cm鈥?, respectively. These values are in excellent agreement with those calculated on the basis of the approximate force field model. Experiments on coadsorption of 14N2 and CO have shown formation of Ni+(CO)(14N2) complexes that were characterized by CO and 14N鈥?sup>14N stretchings at 2098 and 2305 cm鈥?, respectively. The reasons for simultaneous coordination of two 14N2 (or one 14N2 and one CO) molecules to one Ni+ site and the nature of the bonds in the different complexes are discussed.