Tuning Lewis acidity using the reactivity of “frustrated Lewis pairs”: facile formation of phosphine-boranes and cationic phosphonium-boranes
作者:Gregory C. Welch、Lourdes Cabrera、Preston A. Chase、Emily Hollink、Jason D. Masuda、Pingrong Wei、Douglas W. Stephan
DOI:10.1039/b704417h
日期:——
phosphonium-boranes [R(3)P(C(6)F(4))B(C(6)F(5))(2)](+) and [R(2)PH(C(6)F(4))B(C(6)F(5))(2)](+) or into the neutral phosphino-boranes R(2)P(C(6)F(4))B(C(6)F(5))(2). This new reactivity provides a modular route to a family of boranes in which the steric features about the Lewis acidic center remains constant and yet the variation in substitution provides a facile avenue for the tuning of the Lewis acidity. Employing
“沮丧的路易斯对”的概念涉及供体和受体位点,在这些位点中,空间拥挤阻止了路易斯酸碱加合物的形成。在空间上需要膦和硼烷的情况下,这种自动猝灭的缺乏促使对B的碳原子发生亲核攻击,然后进行氟化物转移,从而得到两性离子硼酸硼酸盐[R(3)P(C(6)F(4))BF (C(6)F(5))(2)]和[R(2)PH(C(6)F(4))BF(C(6)F(5))(2)]。这些可以很容易地转化成阳离子phospho硼烷[R(3)P(C(6)F(4))B(C(6)F(5))(2)](+)和[R(2 )PH(C(6)F(4))B(C(6)F(5))(2)](+)或进入中性膦硼烷R(2)P(C(6)F(4 ))B(C(6)F(5))(2)。这种新的反应性提供了通往硼烷家族的模块化途径,其中路易斯酸中心的空间特征保持恒定,而取代基的变化为路易斯酸的调节提供了简便的途径。使用Gutmann-Beckett和Childs