Complexes of [Re(CO)3Cl] with different oxidation states of the polyfunctional bmtz/H2bmtz ligand system (bmtz=3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine)

Combining fac-Re(CO)₃Cl] with components of the ligand redox system bmtz/bmtz⁻/H₂bmtz/H₂bmtz⁻ (bmtz=3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine) has led to the isolation of the complexes (H₂bmtz)Re(CO)₃Cl, (μ-H₂bmtz)Re(CO)₃Cl]₂ and (μ-bmtz)Re(CO)₃Cl]₂. Other species characterized were (bmtz)Re(CO)₃Cl (UV/Vis, IR), (H₂bmtz)Re(CO)₃Cl]⁻ (UV/Vis, IR, EPR), {(μ-H₂bmtz)Re(CO)₃Cl]₂}⁻ (UV/Vis, IR, EPR) and {(μ-bmtz)Re(CO)₃Cl]₂}⁻ (UV/Vis, IR, X band and high-field EPR). The results confirm bmtz as very strong and H₂bmtz as moderate π acceptor ligand versus one or two chelate-bonded low-valent metal centers. Reactivity is observed in terms of oxidative proton and reductive chloride dissociation.