Interaction of water, alkyl hydroperoxide, and allylic alcohol with a single-site homogeneous Ti-Si epoxidation catalyst: A spectroscopic and computational study
Urakawa, A; Bürgi, T; Skrabal, P; Bangerter, F; Baiker, A
| HERO ID | 1071137 |
|---|---|
| In Press | No |
| Year | 2005 |
| Title | Interaction of water, alkyl hydroperoxide, and allylic alcohol with a single-site homogeneous Ti-Si epoxidation catalyst: A spectroscopic and computational study |
| Authors | Urakawa, A; Bürgi, T; Skrabal, P; Bangerter, F; Baiker, A |
| Journal | Journal of Physical Chemistry B |
| Volume | 109 |
| Issue | 6 |
| Page Numbers | 2212-2221 |
| Abstract | Tetrakis(trimethylsiloxy)titanium (TTMST, Ti(OSiMe3)4) possesses an isolated Ti center and is a highly active homogeneous catalyst in epoxidation of various olefins. The structure of TTMST resembles that of the active sites in some heterogeneous Ti-Si epoxidation catalysts, especially silylated titania-silica mixed oxides. Water cleaves the Ti-O-Si bond and deactivates the catalyst. An alkyl hydroperoxide, TBHP (tert-butyl hydroperoxide), does not cleave the Ti-O-Si bond, but interacts via weak hydrogen-bonding as supported by NMR, DOSY, IR, and computational studies. ATR-IR spectroscopy combined with computational investigations shows that more than one, that is, up to four, TBHP can undergo hydrogen-bonding with TTMST, leading to the activation of the O-O bond of TBHP. The greater the number of TBHP molecules that form hydrogen bonds to TTMST, the more electrophilic the O-O bond becomes, and the more active the complex is for epoxidation. An allylic alcohol, 2-cyclohexen-1-ol, does not interact strongly with TTMST, but the interaction is prominent when it interacts with the TTMST-TBHP complex. On the basis of the experimental and theoretical findings, a hydrogen-bond-assisted epoxidation mechanism of TTMST is suggested. |
| Doi | 10.1021/jp048999q |
| Pmid | 16851213 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |
| Is Qa | No |