异金属杂环锗烯的合成与反应

Research on the synthesis and reactivity of germylene has emerged as an intriguing field of organometallic chemistry. The known germylenes were generally supported by pure organic ligands, while the germylene that contains the mixed-metal within its ligand framework has been so far rarely known. Detailed structural and reactivity information on such kind of germylenes that are mediated by adjacent alien metal(s) is not yet available. In the current proposal, we focus on the synthesis of a series of novel alien-metal-involved four-membered N-heterocyclic germylenes derived from the proposed bianionic germylene ligands, which are supposed to be prepared by deprotonation of the known and developing homoleptic germanium(II) amide precursors. Base on this, the related acyclic, five- or more-membered cyclic and cage germylene systems will be developed using the similar strategy. In the experimental exploration, the ligand effect as well as the electronic adjustment/protection around the germanium(II) center will be intensively investigated for an optimal combination to stabilize or activate the targeted products according to the specific instance. The proposed mixed-metal heterocyclic germylene can act as the so-called soft-hard bimetallic reagent to give an expectable performance in the selective coordination reactions. Moreover, the metal centers in close approximity have good chances to cooperate in a synergetic fashion, so as to introduce new reactions and pathways, possibly different from the sole organo-transition metal compounds or the sole organo- main group metal compounds. In addition, the synthetic strategy for the preparation of title compound can also be expanded further to construct the novel ligand system centered by the other metal atom so as to provide new mixed-metal system with potentially interesting structural feature and application.

锗烯的合成与反应是近年有机金属化学的研究热点之一，已有的锗烯大多由纯有机配体支持，配体骨架中含有异金属的锗烯并不多见，人们对此类化合物的结构及反应特性知之甚少。项目在已有及拟合成的系列双伯胺基锗烯的基础上，首次提出以Ge(II)为配体骨架中心来制备系列通用配体、并以之为前体进一步构建异金属N-杂环锗烯，由此带动非环、多员环、笼式体系的制备工作，以期形成系统的异金属参与的锗烯体系。在合成过程中，详细研究配体效应、锗中心保护与电子环境调控等，实现对产物稳定性、反应性的影响。目标体系“异金属参与的锗烯”的构建不仅可望形成软-硬双金属试剂，在选择性配位反应中带来可期应用，且由于双金属间容易发生异金属间的协同作用，有望带来异于单纯过渡金属或单纯主族金属有机化合物的全新反应特性。此外，通过扩展合成，项目还将在“以金属为骨架中心的配体的合成”以及“新的混合金属体系的构筑”方面提供有价值的探索实践。

锗宾的合成与反应近年受到较多关注，但配体骨架中含有异金属的锗宾并不多见，人们对此类化合物的结构及反应特性也知之甚少。本项目以Ge(II)为配体骨架中心制备系列伯胺基锗宾，并以之为前体进一步构建异金属N-杂环锗宾，形成异金属参与的N杂环锗宾体系。项目从H2NR（R=2,6-iPrC6H3、2,6-MeC6H3、Ph等）出发合成N杂环卡宾稳定的双伯胺基锗宾NHC→:Ge(NHR)2，开展其与烷基锂、烷基铝等的反应，探讨其脱质子反应性；探讨其与I、II、III、IV价态主族/过渡金属试剂的反应，构筑各类异金属杂环锗宾。此外，通过扩展合成，进行金属杂环锡宾体系、带邻近供体位点的伯胺锗宾、多锗宾、双酰基硫脲配体、酰基胍配体及新的混合金属体系的构筑等方面的实践研究。项目共合成表征80多个新化合物，并总结出一些有规律的认识。已发表SCI论文十二篇（其中十一篇为第一标注基金），项目研究目标已完成。