A Novel Strategy to Early-Transition Metal pincer complexes of the PCP/POCOP motif

前过渡金属钳形配合物已经显示出迷人的化学性质。从20世纪70年代开始，Fryzuk（和其他人）证明了三齿PNP类配体能够稳定第四族金属的还原并促进它们与二氮的结合。Nishibayashi最近将这项工作扩展到基于吡咯的PNP配体，并且Mindiola已经使用类似的更坚固的框架来催化促进强C-H键（例如甲烷、苯）的活化。PCP/POCOP类配体与这些PNP配体密切相关，其中中心N-供体被形式C-取代。然而，这些配体与前过渡金属的利用尚未实现，这是由于它们的合成路线通常需要在M（N-2）金属中心上氧化加成C-H键。该项目将侧重于开发（五氯苯酚）M/（POCOP）M复合物的替代途径，并研究其衍生化和对小分子的反应性。最后，这类配体的稳定性和模块化的性质将被用来调整金属中心的反应性。最后，这些配合物的结晶性将被用来促进它们在不同物理形式下的反应性。单晶反应性已被证明可以提高工艺的选择性，但目前仅限于后过渡金属。因此，这些化合物将成为研究与前过渡金属类似反应性的理想候选物。

Early-transition metal pincer complexes have shown fascinating chemistry. From the 1970s Fryzuk (and others) demonstrated the tridentate PNP- class of ligands were able to stabilise the reduction of group four metals and facilitate their binding of dinitrogen. This work has recently been extended to pyrole-based PNP ligands by Nishibayashi and similar, sturdier, frameworks have been used by Mindiola to catalytically facilitate the activation of strong C-H bonds (e.g. Methane, Benzene).The PCP/POCOP class of ligands are closely related to these PNP ligands, with the central N- donor replaced for a formal C-. However utilisation of these ligands with early-transition metals has not been achieved due to their synthetic route usually requiring the oxidative addition of a C-H bond across a M(N-2) metal centre. This project will focus on developing an alternative route to (PCP)M/(POCOP)M complexes and studying their derivatization and reactivity towards small molecules. Ultimately the stability and modular nature of this class of ligands will be exploited to tune the reactivity of the metal centre.Finally the crystallisability of these complexes will be used in order to facilitate their reactivity in different physical forms. Single-crystal reactivity has been shown to increase the selectivity of processes, however it is currently limited to the late transition metals. As such these compounds will make ideal candidates to investigate analogous reactivity with the early-transition metals.