Observations concerning the inactivity of dimethylhafnocene as a catalyst for the dehydrocoupling of phenylsilane
Observations concerning the inactivity of dimethylhafnocene as a catalyst for the dehydrocoupling of phenylsilane
复制标题
关于二甲基铪茂作为苯基硅烷脱氢偶联催化剂的不活性的观察
DOI：
10.1021/om00026a048
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发表时间：
1993
期刊：
影响因子：
2.8
通讯作者：
J. Harrod
中科院分区：
文献类型：
--
作者：
H. Li;F. Gauvin;J. Harrod
无论是二甲基双茂还是[1，2-双（四氢茚基）乙烷]二甲基锆，1，都不以可感知的速率与苯基硅烷反应。在铪化合物的情况下，这导致对苯基硅烷的脱氢偶联的催化活性的完全掩蔽，而在1的情况下，活性被大大抑制。该行为由MC键对与硅烷的α-键复分解的低反应性控制。由MeLi和PhSiH_3与二氯双茂或[1，2-二（四氢茚基）-乙烷]二氯锆反应生成的催化剂2对PhSiH_3偶联显示出高活性。所得聚合物的分子量明显高于由Cp → TiMe 2和Cp 2 ZrMe 2催化剂衍生的聚合物的分子量，并且茂金属催化剂产生的低分子量环状产物的比例异常低。有人提出，催化剂物种，可能是一个cridido甲硅烷基络合物，在这些新的系统中产生的反应的反应性氢化锂，导致从快速反应的MeLi与PhSiH 3，与氯配合物。
Neither dimethylhafnocene nor [l, 2-bis (tet-rahydroindenyl) ethane] dimethylzirconium, 1, reacts at an appreciable rate with phenylsilane. In the case of the hafnium compound, this results in complete masking of catalytic activity toward dehydrocoupling of phenylsi-lane, whilein the case of 1 activity is greatly suppressed. This behavior is governed by the low reactivity of the MC bonds toward a-bond metathesis with silanes. Catalysts generated by reaction ofMeLi and PhSiH3 with hafnocene dichloride or[l, 2-bis (tetrahydroindenyl)-ethane] dichlorozirconium, 2, show high activities toward PhSiH3 coupling. The molecular weights ofthe resulting polymers are significantly higher than those of polymers derived from Cp¡ TiMe2 and Cp2ZrMe2 catalysts, and the hafnocene catalyst gives unusually low proportions of low molecular weight cyclic products. It is proposed that the catalyst species, probably a hydrido silyl complex, in these new systems are generated by reaction of a reactive lithium hydride, resulting from rapid reaction of MeLi with PhSiH3, with the chloro complexes.