A Three-Stage Mechanistic Model for Ammonia鈥揃orane Dehydrogenation by Shvo鈥檚 Catalyst
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- 作者：Zhiyao Lu ; Brian L. Conley ; Travis J. Williams
- 刊名：Organometallics
- 出版年：2012
- 出版时间：October 8, 2012
- 年：2012
- 卷：31
- 期：19
- 页码：6705-6714
- 全文大小：553K
- 年卷期：v.31,no.19(October 8, 2012)
- ISSN：1520-6041
文摘
We propose a mechanistic model for three-stage dehydrogenation of ammonia鈥揵orane (AB) catalyzed by Shvo鈥檚 cyclopentadienone-ligated ruthenium complex. We provide evidence for a plausible mechanism for catalyst deactivation and the transition from fast catalysis to slow catalysis and relate those findings to the invention of a second-generation catalyst that does not suffer from the same deactivation chemistry. The primary mechanism of catalyst deactivation is borazine-mediated hydroboration of the ruthenium species that is the active oxidant in the fast catalysis case. This transition is characterized by a change in the rate law for the reaction and changes in the apparent resting state of the catalyst. Also, in this slow catalysis situation, we see an additional intermediate in the sequence of boron, nitrogen species, aminodiborane. This occurs with concurrent generation of NH3, which itself does not strongly affect the rate of AB dehydrogenation.