Thermochemistry and Bond Nature of Oxo and Thio Ligands in Rhenium(V) Catalysts and Rhenium(VII) Intermediates: Density Functional Calculations

摘要

> Models of dithiolate rhenium(V)–oxo and –thio complexes and Re VII (Re VII O ₂ and Re VII OS) intermediates are studied computationally using DFT(B3LYP). The analysis of the Re–E bond (E = O, S) shows that the two lone pairs (P _x , P _y ) on the oxo and thio ligands are strongly polarized to the Re V and Re VII centers, forming partial π bonds, which agree with the bond‐order analysis of 2 (one σ + two partial π bonds). The lone pairs on the thio ligands are less polarized than on the oxo ligand. The Re V O and Re VS bond strengths are calculated to be approximately 163.7?±?1.8 kcal?mol –1 and 123?±?3 kcal?mol –1 , respectively. The Re VII O and Re VII S bond strengths are calculated to be 118.7?±?1.2 kcal?mol –1 and 80.5?±?3.5 kcal?mol –1 , respectively. The calculated oxo– and thio–rhenium bond strengths and the thermochemistry of the OAT (oxygen‐atom transfer) cycle support that Re VII O ₂ and Re VII OS are the key intermediates in the OAT (oxygen atom transfer) and SAT (sulfur atom transfer) reactions.