Investigation on the Intramolecular Proton Transfer Mechanism of [Cp2MHn](Cp=C5H5, M=Mo, W, Re; n=1∼2) with tBuBCl2

Abstract Transition-metal hydrides play a critical role in catalysis and metal-mediated transformations. Experimental results show that in the reactions of (C 5 H 5 ) 2 MH n (M=Mo and W) with t BuBCl 2 , a zwitterionic trihydride, [CpMH 3 ( η 5 -C 5 H 4 BCl 2 R)], is formed instead of salt-like compounds. To elucidate the reaction mechanism and the influence factors in this process, the intramolecular hydrogen atom transfer mechanism of metallocene hydrides (C 5 H 5 ) 2 MH n (M=Mo, W, Re; n=1∼2) with t BuBCl 2 was studied in detail using density functional theory calculations. The calculated results show that the reaction mechanisms of the Cp 2 MH n (M=Mo, W, Re; n=1∼2) with t BuBCl 2 are similar. Borane first attacks the Cp-ring and hydrogen migrates from the Cp ring to the M center, converting the dihydride starting material into a trihydride product or the monohydride into a dihydride product and forming the zwitterionic metal-hydride compounds. In n-pentane, Cp 2 WH 2 + t BuBCl 2 and Cp 2 ReH + t BuBCl 2 reactions can be occurred easily and no diene intermediate forms in the reaction process. The formation of [CpMoH 3 ( η 5 -C 5 H 4 B t BuCl 2 )] in the Cp 2 MoH 2 + t BuBCl 2 reaction is difficult due to the low HOMO energy of Cp 2 MoH 2 . Due to the d 0 electron configuration of Ta, the title reaction cannot occur between CpTaH 3 and t BuBCl 2 .