Intramolecular C−H Activation Reactions of Molybdenacyclobutanes

Molybdenacyclobutane complexes can be prepared by reaction of Cp*Mo(NO)(CHCMe3) (formed spontaneously by loss of neopentane from Cp*Mo(NO)(CH2CMe3)2 (1) under ambient conditions) with cyclic olefins, including cyclopentene, cycloheptene, and cyclooctene. The cyclopentene metallacyclobutane orients the metallacycle bridgehead protons cis to each other. A trans arrangement is observed for the cyclooctene congener, and both cis and trans orientations occur for the cycloheptene species. The reaction of 1 with cyclohexene initially forms a metallacyclobutane that then undergoes an allylic C−H activation to form an allyl−alkyl-coupled product with the concomitant loss of H2. The analogous allyl−alkyl structure is also observed as the thermodynamic product for the reactions of cycloheptene and cyclooctene with 1. The cyclooctene allyl−alkyl compound (5C) can be converted to an η2-diene complex by heating with pyridine. Alternatively, heating of 5C in the presence of a variety of olefins displaces the diene ligand that can then be isolated in its unbound state.

钼环丁烷复合物可通过环戊烯、环己烯和环辛烯等环烯烃与Cp*Mo(NO)(CHCMe3)（在室温下由Cp*Mo(NO)(CH2CMe3)2(1)自发脱去新戊烷生成）的反应制备。环戊烯金属环丁烷使金属环桥头氢原子处于相互顺式构型。环辛烯同系物呈现反式排列，而环庚烯物种则同时存在顺式和反式构型。1与环己烯的反应最初形成金属环丁烷，随后通过烯丙基C-H活化形成烯丙基-烷基偶联产物，伴随氢气的释放。类似地，环庚烯和环辛烯与1的反应也观察到烯丙基-烷基结构作为热力学产物。通过加热与吡啶作用，环辛烯烯丙基-烷基化合物(5C)可以转化为η2-二烯复合物。另外，在多种烯烃存在下加热5C，可置换二烯配体，随后可将其以未结合状态分离出来。