Solid state structure of a rhenium bibenzimidazole complex

Re(CO)₅Br readily forms a complex with 2,2′-bibenzimidazole (bbimH₂) of the general composition (bbimH₂)Re(CO)₃Br, 1. The complex was characterized by NMR, IR, electronic and emission spectroscopy. The orange-brown compound is sparingly soluble in apolar solvents but could be crystallized from a DMF/toluene mixture. An X-ray structural investigation shows that the rhenium ion has a distorted octahedral geometry. Nitrogen atoms of the bibenzimidazole are trans to two carbonyl ligands. The secondary amine protons of the bibenzimidazole ligand form a hydrogen bond to the amide oxygen of a DMF molecule; N3–O4 2.725(7)?Å, N4–O4 2.761(7)?Å. The bending angle of the two benzimidazole units is 168°; the greatest deviation from planarity within the ligand is 0.14?Å. Crystal data: monoclinic, space group P2₁/n, a?=?10.9743(2), b?=?12.9182(2), c?=?15.1864(3)?Å, β?=?91.647(1)°, V?=?2152.06(7)?ų, T?=??90°C, Z?=?4, R ₁?=?0.025, wR ₂?=?0.062 for 4296 reflections with F _o?> 4σ(F _o) out of 4886 independent reflections.