Synergic Effects Between N‑Heterocyclic Carbene and Chelating Benzylidene–Ether Ligands Toward the Initiation Step of Hoveyda–Grubbs Type Ru Complexes

Synergic effects between ancillary N-heterocyclic carbenes
[(1,3-bis­(2,4,6-trimethylphenyl)-1,3-imidazoline-2-ylidene
or 1,3-bis­(2,6-diisopropylphenyl)-1,3-imidazoline-2-ylidene]
and chelating benzylidene–ether ligands were investigated by
studying initiation rates and kinetic profiles of Hoveyda–Grubbs
(HG) type Ru complexes. A newly designed Ru-benzylidene-oxazinone
precatalyst 4 was compared with Grela and Blechert complexes
bearing modified isopropyloxy chelating leaving groups
and with the standard HG complex to understand how the ancillary and
the leaving ligands interact and influence the catalytic activity.

本研究针对辅助N-杂环卡宾（N-heterocyclic carbenes）——即[(1,3-双(2,4,6-三甲基苯基)-1,3-咪唑啉-2-亚基]或[1,3-双(2,6-二异丙基苯基)-1,3-咪唑啉-2-亚基]——与螯合亚苄基醚配体之间的协同效应，通过考察霍维达-格拉布斯（Hoveyda–Grubbs, HG）型钌（Ru）配合物的引发速率与动力学曲线展开了研究。为阐明辅助配体与离去配体的相互作用方式及其对催化活性的影响，本研究将全新设计的钌-亚苄基-恶嗪酮预催化剂4，与带有改性异丙氧基螯合离去基团的格雷拉（Grela）配合物、布雷克特（Blechert）配合物以及标准HG配合物进行了对比分析。