Transition Metal Sigma Bond Complexes

Michael Heinekey，华盛顿大学化学系，由无机、生物无机和有机金属化学项目资助，研究金属-二氢和金属-烷烃相互作用。具体而言，该项目将针对：(1)利用核磁共振波谱和H/D/T标记研究长链二氢配合物的结构和动力学；(2)利用磁不对称性测量对称顺式二氢化物的交换耦合；(3) C-H和Si-H键等sigma键与CO光挤压或硅基阳离子试剂氯离子萃取产生的亲电性金属中心配位；(3)低势垒动力学，包括利用极低温核磁共振光谱和同位素取代测量顺式H2 /H体系的动力学同位素效应；(3)利用中性和/或阳离子Ir(I)络合物对烃类碳氢键进行分子间活化和可能的功能化，从而激活吡唑环中的强碳氢键。目前均相催化研究的一个重要目标是了解金属与底物（如二氢）的结合和活化。与金属中心相互作用仅呈现sigma键的烷烃和硅烷以前只能通过间接测量获得有关这些物种的信息，但在本研究中，它们将直接观察。此外，未来科学家的教育和培训以及新的核磁共振方法的发展是这项工作的主要影响。

Michael Heinekey, Department of Chemistry, University of Washington is supported by the Inorganic, Bioinorganic and Organometallic Chemistry Program for explorations of metal-dihydrogen and metal-alkane interactions. Specifically, the project will target: (1) The structure and dynamics of elongated dihydrogen complexes using NMR spectroscopy and H/D/T labels; (2) Exchange coupling in symmetrical cis dihydrides using magnetic inequivalence to measure couplings; (3) Coordination of sigma bonds such as C-H and Si-H bonds to electrophilic metal centers generated by photoextrusion of CO or by chloride abstraction using silyl cation reagents; (3) Low barrier dynamics, including the measurement of kinetic isotope effects, of cis H2 /H systems using very low temperature NMR spectroscopy and isotope substitution; (3) Intramolecular activation of the strong C-H bonds in pyrazolyl rings by intermolecular activation and possible functionalization of hydrocarbon C-H bonds using neutral and/or cationic Ir(I) complexesAn important current goal of research in homogeneous catalysis is to understand the metal binding and activation of substrates such as dihydrogen, alkanes and silanes which present only sigma bonds for interaction with the metal center Information about these species has previously been available only through indirect measures, but in this study they will be directly observed. In addition, the education and training of future scientists and the development of new NMR methods are major impacts of this work.