Ligand‐ and Metal‐Based Reactivity of a Neutral Ruthenium Diolefin Diazadiene Complex; The Innocent, the Guilty, and the Suspicious
Coordination of the diazadiene diolefin ligand trop2dad to ruthenium leads to various complexes of composition [Ru(trop2dad)(L)]. DFT studies indicate that the closed‐shell singlet (CSS), open‐shell singlet (OSS) and triplet electronic structures of this species are close in energy, with the OSS state being the lowest in energy for all tested functionals. Singlet state CASSCF calculations reveal a significant multireference character for these complexes. The closed‐shell singlet wavefunction dominates, but these complexes have a significant (~8‐16%) open‐shell singlet [d7 Ru(I)(L)(trop2dad●‐] contribution mixed into the ground state. In agreement with their ambivalent electronic structure, these complexes reveal both metal and ligand centered reactivity. Most notably are the reactions with AdN3, diazomethane, and a phosphaalkyne leading to scission of the C‐C bond of the diazadiene moiety of the trop2dad ligand, resulting in net (formal) nitrene, carbene or P‐C insertion in the dad C‐C bond, respectively. Supporting DFT studies reveal that several of the ligand‐based reactions proceed via low barrier radical‐type pathways, involving the dad●‐ ligand radical character of the OSS or triplet species.
Authors:
Vivek Sinha, Bruno Pribanic, Bas de Bruin, Monica Trincado, Hansjörg Grützmacher
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