Tricarbonylmanganese(I) and –rhenium(I) Complexes of Imidazol‐Based Phosphane Ligands: Influence of the Substitution Pattern on the CO Release Properties

Tricarbonylmanganese(I) and ‐rhenium(I) complexes of the imidazolylphosphane ligands tris(imidazol‐2‐yl)phosphane (2‐TIPH), tris(N‐methylimidazol‐2‐yl)phosphane (2‐TIPNMe), and tris[2‐isopropylimidazol‐4(5)‐yl]phosphane (4‐TIPiPr) as well as the phosphane oxide (4‐TIPOiPr) and sulfide (4‐TIPSiPr) ligands were prepared. These tris(imidazolyl) ligands act as N,N,N‐tripodal chelating ligands. The solid‐state structures of the manganese complexes [(2‐TIPNMe)Mn(CO)3]OTf and [(4‐TIPSiPr)Mn(CO)3]OTf as well as the rhenium compound [(4‐TIPOiPr)Re(CO)3]OTf were determined by X‐ray diffraction. The potential of these complexes as photoactivatable CO‐releasing molecules (CORMs) was studied with the UV/Vis spectroscopy‐based myoglobin assay. Within the series of compounds prepared, the substitution pattern of the imidazolyl groups was found to significantly influence the CO‐release efficiency and stoichiometry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)