Ambidentate coordination of the tripyridyl ligands 2,2′:6′,2″‐terpyridyl, tris(2‐pyridyl)‐amine, tris(2‐pyridyl)methane and tris(2‐pyridyl)phosphine to carbonylrhenium centres: Structural and spectroscopic studies

The reactions of [Re(CO) 5 Cl] with the ligands tpy (2,2′:6′,2″‐terpyridine), py 3 N {tris(2‐pyridyl)‐amine}, py 3 CH {tris(2‐pyridyl)methane}, and py 3 P {tris(2‐pyridyl)phosphine} in toluene solution realize compounds with the general formulation [Re(ligand)(CO) 3 Cl] in which the tripyridyl ligands are bidentate. X‐ray structural determinations of fac ‐[Re(typ)(CO) 3 Cl].H 2 O and fac ‐[Re(py 3 N)(CO) 3 Cl] confirm these assignments. [Re(tpy)(CO) 3 Cl].H 2 O (C 18 H 13 ClN 3 O 4 Re) is monoclinic, space group P 2 1 / n , with cell dimensions a = 7.432(2) Å, b = 17.016(4) Å, c = 14.466(2) Å, β = 93.51(2)°, and Z = 4; full‐matrix least‐squares refinement on 2435 reflections with I ⩾ 2.5σ( I ) converged to a final R = 0.028 and R w = 0.029. [Re(py 3 N)(CO) 3 Cl] (C 18 H 12 ClN 4 O 3 Re) is triclinic, space group P 1 with cell dimensions a = 13.761(2) Å, b = 14.636(6)Å, c = 11.110(2) Å, α = 110.70(2)°, β = 102.45(2)°, γ = 107.48(2)°, and Z = 4; full‐matrix least‐squares refinement on 3459 reflections with I ⩾ 2.5σ( I ) converged to a final R = 0.038 and R w = 0.039. If the synthetic procedure is undertaken under irradiation by visible light, for the ligand py 3 N a species [Re(py 3 N)(CO) 2 Cl] (characterized by infrared spectroscopy and conductance measurements) is also formed, in which the ligand py 3 N is tridentate. No analogous tridentate species is formed with the ligands tpy or py 3 P, although there is evidence that it also forms for py 3 CH.