Synthesis of Bis(indenyl)zirconium Dihydrides and Subsequent Rearrangement to η5,η3-4,5-Dihydroindenediyl Ligands: Evidence for Intermediates during the Hydrogenation to Tetrahydroindenyl Derivatives

Exposure of η9,η5-bis(indenyl)zirconium sandwich complexes to 4 atm of H2 resulted in facile
oxidative addition to furnish the corresponding zirconocene dihydrides, (η5-C9H5-1,3-R2)2ZrH2 (R = SiMe3,
SiMe2Ph, CHMe2). Continued hydrogenation completed conversion to the tetrahydroindenyl derivatives,
(η5-C9H9-1,3-R2)2ZrH2. Deuterium labeling studies established that dihydrogen (dideuterium) addition to
the benzo rings is intramolecular and stereospecific, occurring solely from the endo face of the ligand,
proximal to the zirconium. In the absence of dihydrogen, the bis(indenyl)zirconium dihydrides rearranged
to new zirconium monohydride complexes containing an unusual η5,η3-4,5-dihydroindenediyl ligand, arising
from metal-to-benzo ring hydrogen transfer. Mechanistic studies, including a normal, primary kinetic isotope
effect measured at 23 °C, are consistent with a pathway involving regio- and stereoselective insertion of
a benzo CC bond into a zirconium hydride. The stereochemistry of the insertion reaction, and hence the
η5,η3-4,5-dihydroindenediyl product, is influenced by the presence of donor ligands and controlled by the
preferred conformation of the indenyl rings. Exposure of the zirconium hydrides containing the η5,η3-4,5-dihydroindenediyl rings to 1 atm of dihydrogen afforded the tetrahydroindenyl zirconium dihydride complexes,
establishing the intermediacy of this unusual coordination environment during benzo ring hydrogenation.

将η9,η5-双( indenyl)锆 sandwich 复合物暴露于4个大气压的氢气中，导致其轻易地发生氧化加成，从而生成相应的锆辛烯二氢化物，(η5-C9H5-1,3-R2)2ZrH2（R = SiMe3, SiMe2Ph, CHMe2）。持续的氢化过程使化合物完全转化为四氢 indenyl 衍生物，(η5-C9H9-1,3-R2)2ZrH2。氘标记研究证实，氢气（二氘）添加到苯环中是分子内和立体特异的，仅从配体近锆原子端的endo面进行。在缺乏氢气的情况下，双( indenyl)锆二氢化物发生重排，形成含有不寻常的η5,η3-4,5-二氢 indenene 双阴离子配体的锆单氢化物复合物，该配体源于金属至苯环的氢转移。机理研究，包括在23°C测量的正常、一级同位素效应，与涉及苯环C≡C键区域和立体选择性插入锆氢化物的途径一致。插入反应的立体化学，以及因此η5,η3-4,5-二氢 indenene 双阴离子产物，受到供体配体存在的影响，并受indenyl环优选构象的控制。将含有η5,η3-4,5-二氢 indenene 双阴离子环的锆氢化物暴露于1个大气压的氢气中，得到了四氢 indenyl 锆二氢化物复合物，从而确立了这种不寻常配位环境在苯环氢化过程中的中间体地位。