Synthesis and solution stability of water-soluble κ 2 N,κO-bis(3,5-dimethylpyrazolyl)ethanol manganese(i) tricarbonyl bromide (CORM-ONN1).

The reaction of (OC)(5)MnBr with bis(3,5-dimethyl-1-pyrazolyl)methane yields [{(Pz(Me2))(2)CH2}Mn(CO)(3)Br] (1). The use of tridentate heteroscorpionates such as bis(3,5-dimethyl-1-pyrazolyl) acetic acid and 2,2-bis(3,5-dimethyl-1-pyrazolyl) ethanol leads to the formation of mononuclear [(OC)(3)Mn{(Pz(Me2))(2)CH-CO2}] (2) and [(OC)(3)Mn{(Pz(Me2))(2)CH-CH2OH}]Br (3, CORM-ONN1). Salt-like photoCORM 3 is soluble in aqueous media up to a concentration of 200 mu M, non- toxic up to an approx. 65 mu M solution and releases all carbonyl ligands upon irradiation. The molecular complexes 1 and 2 are insoluble in aqueous solutions. CORM-ONN1 (3) slowly degrades in methanol yielding iCORM 4, consisting of the complex cation [{(Pz(Me2))(2)CH-CH2OH}{(Pz(Me2))(2)CH-CH2O}Mn](+) and the [Mn(CO)(5)](-) counter anion with the cations linked to a dimeric unit by intermolecular hydrogen bridges between the alcohol and alkoxide functionalities.