Bimetallic Ni(II) complex with carboxylate bridging for homogeneous hydrogenation of alkenes with NaBH4

Abstract

In this study, we present the synthesis and full characterization of the dimer Ni(II) complex, [Ni2(dpaa)2(bpy)2(SO4)(H2O)]CH3OH, (dpaa = diphenyl acetic acid, bpy = 2,2′-bipyridine) with an N2O4 donor set and its hydrogenation activity on linear and cyclic alkenes (1-octene, t-2-octene, 1-hexene, cyclohexene, cyclopentene, benzene and styrene) with NaBH4 as a hydrogen source. 1-Octene and 1-hexene were reduced to the corresponding alkanes as the major products (81.3 and 91.2%, respectively), and the substrate isomerized the terminal alkenes to a mixture of internal alkenes as minor products (1–4%) under the studied conditions (subs/cat/reduct. 100/1/1 in methanol, 40 °C, 6 h). To optimize the reaction conditions for the reduction of styrene to ethyl benzene in methanol, the effect of subs./NaBH4 ratio, solvent and temperature were also investigated.