Decamethylscandocinium-hydrido-(perfluorophenyl)-borate: fixation and tandem tris(perfluorophenyl)-borane catalysed deoxygenative hydrosilation of carbon dioxide
Decamethylscandocinium-hydrido-(perfluorophenyl)-borate: fixation and tandem tris(perfluorophenyl)-borane catalysed deoxygenative hydrosilation of carbon dioxide
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DOI：
10.1039/c3sc50145k
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发表时间：
2013-01-01
期刊：
影响因子：
8.4
通讯作者：
Eisenstein, Odile
中科院分区：
文献类型：
--
作者：
Berkefeld, Andreas;Piers, Warren E.;Eisenstein, Odile
这项工作是针对研究的能力，结构确定的，强路易斯酸性金属中心的影响催化还原固定的小分子底物CO2。将离子对[Cp*Sc-2][HB（C6 F5）（3）] 1（CIP）的溶液或固体样品（其中高度亲电的十甲基-钪茂阳离子和[HB（C6 F5）]（-）作为氢化物当量的潜在反应源缔合）暴露于CO2选择性地产生离子对[Cp*Sc-2][HCO 2B（C6 F5）（3）] 2（CIP）。2（CIP）的溶液和固态结构分析结果表明，[Cp*Sc-2]（+）和[HCO 2 B（C6 F5）（3）]（-）离子缔合，而不是B（C6 F5）（3）-加合物形成中性Cp*Sc-2-甲酸盐。在B（C6 F5）（3）助催化剂和过量三乙基硅烷的存在下，由1（CIP）形成2（CIP）引发CO2催化脱氧硅氢化成CH 4。离子对1和2，硼烷助催化剂，和硅烷在催化反应中的作用进行了研究，通过NMR光谱的机理。发现插层形成的3，3，7，7-四乙基-3，7-二硅杂-4，6-二氧杂壬烷产物通过形成分离的离子对[Cp*Sc-2（kappa（2）-（Et 3SiO）（2）CH 2）][HCO 2 {B（C6 F5）（3）}（n）]（n = 1，2）促进[HCO 2 B（C6 F5）（3）]（-）解离以得到2（SIP）而对总反应速率施加加速作用。密度泛函理论计算表明，1（CIP）与CO2反应生成2（CIP）是放能的，没有明显的能垒。这项工作奠定了基础，为今后的研究这种反应离子对的背景下，小分子化学。
This work was directed at studying the capability of structurally defined, strongly Lewis-acidic metal centers to effect catalytic reductive fixation of the small molecule substrate CO2. Exposing solutions or solid samples of the ion pair [Cp*Sc-2][HB(C6F5)(3)] 1(CIP), in which the highly electrophilic decamethyl-scandocene cation and [HB(C6F5)](-) as a potentially reactive source of hydride equivalents are associated, to CO2 selectively produces ion pair [Cp*Sc-2][HCO2B(C6F5)(3)] 2(CIP). The results of solution and solid state structural analysis of 2(CIP) imply ionic association of [Cp*Sc-2](+) and [HCO2B(C6F5)(3)](-) rather than B(C6F5)(3)-adduct formation to neutral Cp*Sc-2-formate. In the presence of B(C6F5)(3) co-catalyst and excess triethylsilane, the formation of 2(CIP) from 1(CIP) initiates the catalytic deoxygenative hydrosilation of CO2 to CH4. The roles of ion pairs 1 and 2, borane co-catalyst, and silane in the catalytic reaction were studied mechanistically by NMR spectroscopy. Intermediately formed 3,3,7,7-tetraethyl-3,7-disila-4,6-dioxanonane product was found to exert an accelerating effect on the overall reaction rate by promoting [HCO2B(C6F5)(3)](-) dissociation to give 2(SIP) through formation of separated ion pairs [Cp*Sc-2(kappa(2)-(Et3SiO)(2)CH2)][HCO2{B(C6F5)(3)}(n)], n = 1, 2. DFT calculations show that the formation 2(CIP) from the reaction of 1(CIP) with CO2 is exoergic and without significant energy barriers. This work lays the basis for future studies of reactive ion pairs of this kind in the context of small molecule chemistry.