Rhenium(I) di- and tri-carbonyl compounds of polypyridyl-like ligands: electrochemical reactions of fac-[Re(CO)3(dpk)Cl] (dpk = di-2-pyridyl ketone) with electrophiles and Group I and II metal ions
Abstract
In contrast to the facile formation of fac-[Re(CO)3(dpk)Cl] 1 from the reaction between [Re(CO)5Cl] and dpk [(C5H4N)2C(O)], in refluxing toluene, [Re(CO)5Cl] was recovered unchanged when di-2-pyridylamine, dpa [(C5H4N)2NH], was allowed to react with [Re(CO)5Cl] under a variety of conditions. However, a mixture of [Re(CO)5Cl] 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 ReI(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)2C(O)(OH)}] and cis-[Re(CO)2(PPh3){(C5H4N)2C(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.