Cooperative Reactivity and Catalysis using Abundant Metal Clusters.

在过去的十年中，对多核过渡金属物种的设计和合成的集中努力已经加强。在某种程度上，这些努力源于试图模拟多核金属酶促进的困难的多电子转换。例子包括光系统II中的Mn-O辅因子，以及固氮酶中的碳化物轴承[FeMo]辅因子。虽然已经报道了过多的过渡金属簇，但大多数是高度稳定的物种，这是由于配位饱和和分子轨道构型，其特征在于由常用的配体如CO产生的大HOMO/LUMO间隙。为了设计具有更高反应性的过渡金属簇的目标，我们正在研究第一行后期过渡金属的簇，这些过渡金属与便宜的容易获得的配体组装，配体小到足以允许簇形成，但大到足以确保配位不饱和。 这些复合物表现为一个独特的和未充分研究的类集群，不同的电子计数偏离理论预测，低躺顺磁激发态，可以允许低势垒反应途径，耐受一系列的官能团，和一个显着的倾向，共同惰性的C-H，C-C和C-O键的合作激活。 这些簇作为骨架键重排的独特催化剂的潜力是显而易见的，但到目前为止，对它们的应用还没有足够的基本认识。 该项目的短期目标旨在更好地了解高活性晚期金属簇合物（如[（iPr 3 P）Ni] 5 H6）的化学性质，长期目标是将其在协同键活化中的能力扩展到催化过程。 受碳化物中心[FeMo]辅因子的启发，由间隙原子锚定的更稳健的簇的设计提供了一种簇设计的途径，该途径与严格基于复杂辅助配体设计的簇设计根本不同。

Focused efforts towards the design and synthesis of polynuclear transition metal species have intensified in the last decade. In part, these efforts stem from attempts to mimic the difficult multielectron transformations facilitated by polynuclear metalloenzymes. Examples include the Mn-O cofactor in Photosystem II, as well as the carbide bearing [FeMo] cofactor in Nitrogenase. Although a plethora of transition metal clusters have been reported, the majority are highly stable species, due to coordinative saturation and molecular orbital configurations that feature large HOMO/LUMO gaps that arise from commonly used ligands such as CO.***Towards the goal of designing transition metal clusters that have a more reactive nature we are investigating clusters of the late 1st row transition metals that are assembled with inexpensive readily-available ligands that are small enough to permit cluster formation, but large enough to ensure coordinative unsaturation. These complexes behave as a unique and understudied class of clusters, with varied electron counts that deviate from theoretical predictions, low-lying paramagnetic excited states that may allow low barrier reaction pathways, tolerance to a range of functional groups, and a remarkable propensity for cooperative activation of commonly inert C-H, C-C and C-O bonds. The potential of these clusters as unique catalysts for skeletal bond rearrangements is obvious, but as yet insufficient fundamental understanding is a barrier to their application. The short term goals of this project aim to provide a better understanding of the chemistry of the highly reactive late metal clusters like [(iPr3P)Ni]5H6, with long-term goals of extending its capability in cooperative bond activation to catalytic processes. The design of more robust clusters anchored by interstitial atoms, inspired by the carbide centre [FeMo] cofactor, provides a route to cluster design that is fundamentally different from those based strictly on complex ancillary ligand design.********