Rhenium(I) di- and tri-carbonyl compounds of polypyridyl-like ligands: electrochemical reactions of fac-[Re(CO)(3)(dpk)Cl] (dpk equals di-2-pyridyl ketone) with electrophiles and Group I and II metal ions

In contrast to the facile formation of fac-[Re(CO)(3)(dpk)Cl] 1 from the reaction between [Re(CO)(5)Cl] and dpk [(C5H4N)(2)C(O)], in refluxing toluene, [Re(CO)(5)Cl] was recovered unchanged when di-2-pyridylamine, dpa [(C5H4N)(2)NH], was allowed to react with [Re(CO)(5)Cl] under a variety of conditions. However, a mixture of [Re(CO)(5)Cl] and PPh3 in refluxing toluene followed by a CH2Cl2 solution of dpa gave cis-[Re(CO)(2)(PPh3)(dpa)Cl]. The intermediate involved appears to be a general synthon for the binding of the Re-I(CO)(2)(PPh3)Cl chromophore to a variety of bi-and mono-dentate nitrogen-donor ligands and has been utilized to isolate cis-[Re(CO)(2)(PPh3)(dpk)Cl]. Nucleophilic addition of water at the carbonylic carbon atom of co-ordinated dpk in 1 and cis-[Re(CO)(2)(PPh3)(dpk)Cl] resulted in the hydration of the keto group and formation of fac-[Re(CO)(3){(C5H4N)(2)C(O)(OH)}]. and cis-[Re(CO)(2)(PPh3){(C5H4N)(2)C(O)(OH)}]. The compounds isolated exhibit rich electrochemical and photochemical properties and the potential application of fac-[Re(CO)(3)(dpk)Cl] as an electrochemical sensor for electrophiles and Group I and II metal ions is demonstrated.