Bond elongation in the anion radical of coordinated tetrazine ligands: A crystallographic, spectroscopic and computational study of a reduced {Re(CO)3Cl} complex

► The crystal structure of a reduced {Re(CO)3Cl} has been evaluated for the first time. ► A tetrazine-based bridging ligand (BPTZ) was used. ► Bond lengths follow expectations from calculated SOMO. ► Large azo-type NN and negligible Re-Cl length changes are calculated and observed.