School of Chemistry, University of New South Wales , Sydney, NSW 2052, Australia.
J Am Chem Soc. 2016 Jan 13;138(1):281-8. doi: 10.1021/jacs.5b10583. Epub 2015 Dec 22.
In seeking to create more-stable transition metal-alkane complexes, we generated cationic alkane complexes of the type [(HEB)Re(CO)2(alkane)][Al(OR(f))4] (HEB = η(6)-hexaethylbenzene; alkane = cyclopentane (16) or pentane (17-19); OR(f) = perfluoro-tert-butoxy) via photolysis of the precursor complex [(HEB)Re(CO)3][Al(OR(f))4] (15) in the presence of the added alkane. The alkane complexes were generated in a hydrofluorocarbon (HFC) solvent, most often CF3CH2CF3, which is capable of simultaneously dissolving the ionic complex 15 and a small amount of alkane at low temperature (183 K). Use of the HFC solvent in tandem with the highly fluorinated, solubilizing, weakly coordinating Al(OR(f))4 anion overcomes the technical difficulty of combining ionic species with alkanes in solution without the solvent molecules rapidly displacing the bound alkane ligand, as the alkanes bind in preference to the HFCs to the organometallic fragments employed in this study. The (HEB)Re(CO)2(alkane) complexes are more long-lived than the corresponding neutral alkane complexes [(HEB)W(CO)2(alkane)] and [CpRe(CO)2(alkane)] (Cp = η(5)-cyclopentadienyl), with samples of [CpRe(CO)2(cyclopentane)] decaying significantly more rapidly than (HEB)Re(CO)2(alkane) when present in the same solution. Intramolecular exchange of the methylene group bound to the metal within the cyclopentane ligand in 16 was observed at 212 K, with the 1,2 shifts appearing to be faster than 1,3 shifts.
在寻求合成更稳定的过渡金属-链烷烃配合物时，我们通过在存在添加的链烷烃的情况下用光解前体配合物[(HEB)Re(CO)3][Al(OR(f))4]（15）生成了类型[(HEB)Re(CO)2(链烷烃)][Al(OR(f))4]的阳离子链烷烃配合物（HEB=η(6)-己基苯；链烷烃=环戊烷（16）或戊烷（17-19）；OR(f)=全氟叔丁氧基）。链烷烃配合物是在氢氟碳（HFC）溶剂中生成的，最常见的是 CF3CH2CF3，它能够在低温（183 K）下同时溶解离子配合物 15 和少量的链烷烃。使用 HFC 溶剂与高度氟化、溶解、弱配位的Al(OR(f))4阴离子相结合，克服了在溶液中结合离子物种和链烷烃的技术难题，而无需溶剂分子迅速取代结合的链烷烃配体，因为在这项研究中使用的有机金属片段更喜欢与 HFC 结合而不是与链烷烃结合。[(HEB)Re(CO)2(链烷烃)]（+)配合物比相应的中性链烷烃配合物[(HEB)W(CO)2(链烷烃)]和[CpRe(CO)2(链烷烃)]（Cp=η(5)-环戊二烯基）更稳定，当存在于相同溶液中时，[CpRe(CO)2(环戊烷)]的样品分解速度明显快于[(HEB)Re(CO)2(链烷烃)]（+)。在 212 K 时观察到环戊烷配体中与金属结合的亚甲基基团的分子内交换，1,2 重排似乎比 1,3 重排快。
