Hydrosilylation of Carbonyls Catalyzed by Hydridoborenium Borate Salts: Lewis Acid Activation and Anion Mediated Pathways
作者:Sandeep Rawat、Mamta Bhandari、Vishal Kumar Porwal、Sanjay Singh
DOI:10.1021/acs.inorgchem.0c00646
日期:2020.5.18
multinuclear NMR measurements for catalysts 1 and 2. The combined effect of carbonyl activation via the Lewis acidic hydridoborenium cation and the hydridic nature of the borate counteranion in 1 makes it a more efficient catalyst in comparison to that of carbonyl activation via the predominant Lewis acid activation pathway operating with catalyst 2. The catalytic cycle of 1 showed hydride transfer from
由双(膦酰氨基)酰胺配体支撑的电子不饱和三配位氢硼阳离子[LBH] + [HB(C6F5)3]-(1)和[LBH] + [B(C6F5)4]-(2),被发现是在温和的反应条件下(L = [(2,4,6-Me3C6H2N)P(Ph2)} 2N]氢化一系列脂肪族和芳香族醛和酮的出色催化剂。通过对催化剂1和2的原位多核NMR测量,监测了PhCHO硅氢加氢反应的催化循环的关键步骤。1中路易斯酸氢硼化硼阳离子对羰基的活化作用与硼酸抗衡阴离子的氢化性质共同作用使其成为一种与通过主要的路易斯酸活化途径与催化剂2进行羰基活化相比,催化剂更有效。1的催化循环显示氢化物在第一步中从硼酸盐部分[HB(C6F5)3]-转移到PhCHO,形成[PhCH2-OB(C6F5)3]-,随后与Et3SiH进行σ键易位。产品为PhCH2-O-SiEt3。量子化学计算也支持1的硼酸根阴离子介导的机理。相反,由2催化的反应主要