Manganese Alkane Complexes: An IR and NMR Spectroscopic Investigation
详细信息 查看全文
- 作者：James A. Calladine ; Simon B. Duckett ; Michael W. George ; Steven L. Matthews ; Robin N. Perutz ; Olga Torres ; Khuong Q. Vuong
- 刊名：Journal of the American Chemical Society
- 出版年：2011
- 出版时间：February 23, 2011
- 年：2011
- 卷：133
- 期：7
- 页码：2303-2310
- 全文大小：909K
- 年卷期：v.133,no.7(February 23, 2011)
- ISSN：1520-5126
文摘
Manganese propane and manganese butane complexes derived from CpMn(CO)3 were generated photochemically at 130鈭?36 K with the alkane as solvent and characterized by FTIR spectroscopy and by 1H NMR spectroscopy with in situ laser photolysis. Time-resolved IR spectroscopic measurements were performed at room temperature with the same laser wavelength. The 谓(CO) bands in the IR spectra of the photoproducts in propane are shifted to low frequency with respect to CpMn(CO)3, consistent with formation of CpMn(CO)2(propane). The 1H NMR spectra conform to the criteria for alkane complexes: a high-field resonance for the 畏2-CH protons that shifts substantially on partial deuteration of the alkane and exhibits a coupling constant JC鈭扝 on 13C-labeling of ca. 120 Hz. The NMR spectrum of each system exhibits two diagnostic product resonances in the high-field region for the 畏2-CH protons, corresponding to CpMn(CO)2(畏2-C1鈭?i>H鈭抋lkane) and CpMn(CO)2(畏2-C2鈭?i>H鈭抋lkane) isomers. Partial deuteration of the alkane at C1 results in characteristic strong isotopic perturbation of equilibrium of the 畏2-CH resonance of CpMn(CO)2(畏2-C1鈭?i>H鈭抋lkane). With propane-13C1, the 畏2-CH resonance of CpMn(CO)2(畏2-C1鈭?i>H鈭抋lkane) isomer exhibits 13C satellites with JC鈭扝 = 119 Hz. The corresponding resonance of CpMn(CO)2(畏2-C2鈭?i>H鈭抋lkane) is identified by use of propane-2,2-d2. The lifetimes of the (畏2-C1鈭?i>H鈭抋lkane) isomers of the manganese complexes were determined by NMR spectroscopy as 22 卤 2 min at 134 K (propane) and 5.5 min at 136 K (butane). The corresponding spectra and lifetimes of the CpRe(CO)2(alkane) complexes were measured for reference (CpRe(CO)2(propane) lifetime ca. 60 min at 161 K; CpRe(CO)2(butane) 13 min at 171 K). The lifetimes determined by IR spectroscopy were similar to those determined by NMR spectroscopy, thereby supporting the assignments. These measurements extend the range of alkane complexes characterized by NMR spectroscopy from rhenium and rhodium derivatives to include less stable manganese derivatives.