New ligands for small molecule activation by metal complexes

用金属络合物活化小分子是无机化学中一个成熟的领域。 然而，作为生物圈中最丰富的小分子之一，分子氮由于其固有的缺乏反应性而继续使无机化学家感到沮丧。 这种小分子的稳健性质是由于许多因素，包括大的键离解能（945 kJ/mol）、缺乏偶极矩以及对电子的添加和/或去除的大的势垒。 当然，众所周知，在极端条件下，N2将与H2在活化的铁表面上反应生成氨;这种能量密集型催化转化，称为哈伯-博世过程，满足了全球对NH3衍生肥料的需求。 相比之下，生物系统在环境条件下将分子氮转化为氨;有许多固氮酶的变体，但最常见的是利用铁和钼的蛋白质稳定的硫化物簇作为辅因子（FeMoco）。 虽然发现Haber-Bosch过程的均相版本是世界各地许多团体的目标，但另一个有价值的目标是开发分子氮的新反应，从而形成高价值的有机氮材料，如胺和N-杂环。 该提案概述了一系列旨在加速二氮功能化领域突破的实验。 同样重要的是其他稳定的分子，它们可能通过与配体和金属的适当组合相互作用而被迫进入新的反应模式;例如，二氧化碳（CO2）和烷烃（RH）也是非常稳健的分子，将被视为可能的原料，使用有目的设计的均相催化剂来产生更高价值的材料。

The activation of small molecules by metal complexes is a mature area of inorganic chemistry. Nevertheless, molecular nitrogen, one of the most abundant small molecules in the biosphere, continues to frustrate inorganic chemists due to its intrinsic lack of reactivity. The robust nature of this small molecule is due to a number of factors including, a large bond dissociation energy (945 kJ/mol), the lack of a dipole moment, and a large barrier to addition and/or removal of electrons. Of course, it is well known that under extreme conditions, N2 will react with H2 over an activated iron surface to generate ammonia; this energy-intensive catalytic transformation, known as the Haber-Bosch process, supplies the global need for NH3-derived fertilizers. In contrast, biological systems convert molecular nitrogen into ammonia under ambient conditions; there are a number of variants of the enzyme Nitrogenase but the most common utilize protein-stabilized sulfido-clusters of iron and molybdenum as the cofactor (FeMoco). While discovery of a homogeneous version of the Haber-Bosch process is the goal of a number of groups around the world, another worthwhile goal is to develop new reactions for molecular nitrogen that result in the formation of high-value organonitrogen materials, such as amines and N-heterocycles. This proposal outlines a series of experiments designed to accelerate breakthroughs in the area of dinitrogen functionalization. Also of importance are other stable molecules that might be coerced into new reactivity patterns by interaction with appropriate combinations of ligands and metals; for example, carbon dioxide (CO2) and alkanes (RH) are also very robust molecules that will be examined as possible feedstocks to generate higher-value materials using purposefully designed homogeneous catalysts.