Kinetic and Mechanistic Study with Optically Active, Four-Coordinate Nickel(II) Complexes: Stereoselectivity in Ligand Substitution
作者:Alexander Haus、Michael Raidt、Thomas A. Link、Horst Elias
DOI:10.1021/ic000339m
日期:2000.10.1
of 3.0, as obtained for NiA2 = bis[N-dehydroabietylsalicylaldiminato]nickel(II) reacting with the R- and with the S-enantiomer of H2B = N,N'-disalicylidene-1,2-diamino-4-methylpentane, appears to be the highest stereoselectivity reported so far for ligand substitution in nickel(II) complexes. With NiA2 = R- and S-bis[N-(1-phenylethyl)-5-nitrosalicylaldiminato]nickel(II) and H2B = R- and S-N,N-disalicylidene-1
根据NiA2 + H2B,使用常规和快速扫描停流光度法以及偏光法研究了六个手性双N-烷基水杨基铝二氨基镍(II)配合物NiA2被不同的手性Salen型配体H2B取代的动力学- > NiB + 2HA,在298 K的丙酮中,部分在可变温度下。在大多数情况下,发现配体取代遵循单相二级动力学,速率= kx [NiA2] x [H2B]。确定了在给定体系NiA2 / H2B中对映体的各种组合的二阶速率常数k,在298 K时范围为10(-2)-400 M(-1)s(-1)。 R-NiA2 / R-H2B,S-NiA2 / R-H2B,R-NiA2 / S-H2B和S-NiA2 / S-H2B。发现配体取代易受到手性歧视。二阶速率常数的比值kfast / kslow,对于更快反应的对映异构体,kfast为速率常数k,反之亦然,其范围为1.0-3.0,这取决于NiA2中N-烷基的性质以及在Salen配体