Au<sup>I</sup> Complexes with Planar Tetracoordinate Carbon and Their Catalytic Activity for the Rearrangement of Allylic Acetates: A Computational Study
Miaorun Zhang, Junjing Gu, Yi Zhao
Abstract
High Resolution Image Download MS PowerPoint Slide Since the experimental synthesis of C 2 B 2 H 2 in 2017, the general class of C 2 B 2 R 2 with variable substituent group R has been speculated and is expected. Here we computationally investigate two rhombus molecules C 2 B 2 Me 2 ( a ) and C 2 B 2 t Bu 2 ( b ) which are confirmed to have carbene characteristics arising from charge shift based on the ab initio valence bond (VB) computations. These novel carbene molecules are structurally similar to N-heterocyclic carbenes (IMe and I t Bu). Using them as ligands, six complexes (C 2 B 2 R 2 ) 2 Au I, (C 2 B 2 R 2 )AuCl and (C 2 B 2 R 2 )Au I (R = Me and t Bu) are designed and found to be thermodynamically stable on the basis of density functional theory (DFT) calculations. NBO analyses show that these six complexes contain planar tetracoordinate carbons (ptCs). The first vertical energies of these complexes are consistently red-shifted compared to their ligands C 2 B 2 R 2 . We further explore the reaction mechanism of the rearrangement of allylic acetates catalyzed by (C 2 B 2 R 2 )Au I (R = Me and t Bu) and their analogues (NHC)Au I (NHC = IMe and I t Bu) for comparison. It is found that the rearrangement of allylic acetates catalyzed by (C 2 B 2 R 2 )Au I is feasible both thermodynamically and kinetically, and the concerned energy barriers in the process are lower than those catalyzed by (NHC)Au I . Thus, C 2 B 2 R 2 are promising novel molecules that can be used to rationally design a variety of compounds with ptCs for potential applications in catalysis.