ELECTRONIC AND GEOMETRIC ORIGINS OF THE NON-INNOCENT NATURE OF LIGANDS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 我们建议用多边X射线吸收研究来剖析配位化合物中配体的非无害行为的基本分子细节。配体的非无辜性质最好的宏观特征是基于配体的反应性，其中中心金属成为旁观者，最常见的是立体支架而不是反应中心。在微观上，这转化为具有丰富配体贡献的价轨道(即大配体共价性)。我们已经收集了Ni(II)/Ni(III)氧化还原偶合体系的初步数据，这些数据清楚地证明了我们测量的可行性。我们的数据出人意料地显示了钳型配体PNP的非无辜行为，在有机金属化学和催化的背景下，最初被认为是无害的辅助配体。以前，这种行为主要是在含硫和含氧的配体上观察到的，如二硫烯和儿茶孔。我们首先计划研究两个钳型配体，它们的PCP和PNP组成与一系列第一排过渡金属配位，作为中心金属，它们的形式为单价、二价和三价。鉴于磷的还原能力，我们还将研究只有氮给体的钳形配体，特别是单阴离子NCN体系C6H3[1，3-CH2NiPr2]2。这些拟议的研究是一个更大的项目的一部分，该项目旨在了解作为3D过渡金属离子(当从晚期转移到中期时)和配体中杂原子的性质而导致非无害行为的物理化学因素。我们希望为合成化学家建立指导方针，使其能够先验地预测非无辜行为。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We propose multi-edge x-ray absorption studies to dissect the fundamental molecular details of the non-innocent behavior of ligands in coordination compounds. The non-innocent nature of ligands is best characterized macroscopically by ligand-based reactivity, where the central metal becomes a spectator and most often a steric scaffold rather than a reactive site. Microscopically this translates into valence orbitals that are rich in ligand contribution (i.e. large ligand covalency). We have already collected preliminary data for formally Ni(II)/Ni(III) redox couple system supported with a pincer-type ligand denoted PNP (PNP = N[2-P(CHMe2)2-4-methylphenyl]2) at the Ni L-, Cl and P K-edges that clearly demonstrate the feasibility of our measurements. Our data unexpectedly show the non-innocent behavior of the pincer-type ligand PNP originally thought to be innocent ancillary in the context of organometallic chemistry and catalysis. Previously this behavior was mainly observed for sulfur and oxygen containing ligands, such as dithiolenes and catecholes. We first plan to study two pincer-type ligands with PCP and PNP compositions that are coordinated to a series of first row transition metals as central metals in their formally mono-, di-, and trivalent forms. Given the reducing ability of phosphorus, we will also investigate pincer ligands having only nitrogen donors, specifically the monoanionic NCN system C6H3[1,3-CH2NiPr2]2. These proposed investigations are part of a larger project aiming to understand the physical-chemical factors that can contribute to non-innocent behavior as a function of the 3d transition metal ion (when shifting from late to mid) and the nature of the heteroatom in the ligand. We wish to set up guidelines for synthetic chemists to be able a priori predict non-innocent behavior.