Selective H/D Exchange of Pyridines and Alkylarenes with D<sub>2</sub> Enabled by a Heterometallic Mg–Ni–Mg Polyhydride Complex
Yanping Cai, Mengwei Wang, Yueyue Yang, Xin Xu
Abstract
Heterometallic polyhydride complexes containing main-group metals and transition metals have attracted much attention due to their versatile MH n units and potential metal–metal synergies for molecular transformation. In this work, we report that a heterometallic Mg–Ni–Mg polyhydride complex [( L Mg) 2 NiH 4 ] { L = [(DippNCMe) 2 CH] −, Dipp = 2,6- i Pr 2 C 6 H 3 } is able to catalyze the selective H/D exchange of ortho C(sp 2 )–H bonds of pyridine derivatives with D 2 to obtain deuterium-labeled compounds with high isotopic incorporation. Moreover, benzylic C(sp 3 )–H bonds are also successfully labeled using D 2 in the presence of [( L Mg) 2 NiH 4 ]. Pharmaceuticals with high isotopic incorporation have also been achieved with this catalytic system. Stoichiometric reactions of [( L Mg) 2 NiH 4 ] with pyridines yield the Mg–Ni cooperative mono - and bis - ortho C–H bond activation complexes, i.e., trihydride [( L Mg) 2 NiH 3 (NC 5 H 4 R)(NC 5 H 3 R)] (R = Ph, Et) and dihydride [( L Mg) 2 NiH 2 (NC 5 H 3 Ph) 2 ], which are considered as active intermediates in the catalytic process.