The Distinctive Electronic Structures of Rhenium Tris(thiolate) Complexes, an Unexpected Contrast to the Valence Isoelectronic Ruthenium Tris(thiolate) Complexes.
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
The noninnocent 2-diphenylphosphino-benzenethiolate (DPPBT) ligand containing both phosphorus and sulfur donors delocalizes the electron density in a manner reminiscent of dithiolenes. The electronic structure of the [ReL3]n (L = DPPBT, n = 0, 1+, 2+) complexes was probed with density-functional theory (DFT) and high-level ab initio methods including complete active space self-consistent field (CASSCF and CASPT2) and coupled cluster (CCSD and CCSD(T)). DFT predicts a slight preference for a closed-shell (CS) singlet ground state for the neutral [ReL3]0 and stronger preferences for low-spin ground states for the oxidized [ReL3]+ and [ReL3]2+. High-level ab initio methods confirm a CS singlet with a Re(III) (d4, S = 0) center as the ground state of [ReL3]0. Thus, this neutral Re species has considerably less thiyl radical character than the valence isoelectronic [RuL3]+, which is mainly a Ru(III) (d5, S = 1/2) anti-ferromagnetically (AF) coupled to a thiyl radical (S = 1/2). However, the oxidized derivatives [ReL3]+ and [ReL3]2+ show significant metal-stabilized thiyl radical character like [RuL3]+. Both [ReL3]+ and [ReL3]2+ have major contributions from Re(III) (d4, S = 1) centers AF coupled to thiyl and dithiyl DPPBT ligands. These findings are consistent with the experimental chemistry as [RuL3]+, [ReL3]+, and [ReL3]2+ can add ethylene to form the new C-S bonds, but [ReL3]0 cannot. The thiyl radicals on the S2 position (the S trans to a P donor) serve as the intrinsic electron acceptors in the actual ethylene addition reactions with Ru and Re tris(thiolate) complexes.