We
develop a new implementation of coupled-cluster singles and
doubles (CCSD) optimized for the most recent graphical processing
unit (GPU) hardware. We find that a single node with 8 NVIDIA V100
GPUs is capable of performing CCSD computations on roughly 100 atoms
and 1300 basis functions in less than 1 day. Comparisons against massively
parallel implementations of CCSD suggest that more than 64 CPU-based
nodes (each with 16 cores) are required to match this performance.
The Schlenk equilibrium of Grignard reagents describes the intricate relationships between monomers, aggregates, and exchange products. The core step of the Schlenk equilibrium, formally 2RMgX ⇌ R 2 Mg + MgX 2 , has been subject to computational studies of simple methyl Grignards and NMR determination of thermodynamics. These studies neglect the effect the R group may have on the accessibility of intermediates in the Schlenk equilibrium. In this study, computational reaction discovery tools were employed to thoroughly search the chemical space for feasible dimerizations and pathways to ligand exchange for thiophene Grignards. Three bridged dimers, μ-(Cl, C), μ-(Cl, Cl), and μ-Cl, were found to be vital intermediates, which are stabilized by πinteractions involving the thiophene group. These dimers are approximately as thermodynamically stable as the Grignard monomers and its ligand exchange products, and therefore, their reactivity should be considered when examining mechanisms for aryl Grignard or cross-coupling reactions.
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