Unpredictable Dynamic Behaviour of Ruthenium Chelate Pyrrole Derivatives.

Reaction of [Ru(H)(CO)(PPh)] with an equimolar amount of pyrrole-2-carboxylic acid () leads to the homoleptic chelate derivative k(O,O)-[RuH(CO)(HL)(PPh)] . Prolonged acetonitrile refluxing promotes an unusual k(O,O)- → k(N,O)- dynamic chelate conversion, forming a neutral, stable, air- and moisture- insensitive, solvento-species k(N,O)-[Ru(MeCN)(CO)(L)(PPh)] . Analogously, reaction of with the pyrrole-2-carboxyaldehyde () affords k(N,O)-[RuH(CO)(HL)(PPh)] , , as a couple of functional isomers. Optimized reaction conditions such as temperature and solvent polarity allow the isolation of dominant configurations. Structure is a pyrrolide Ru-carbaldehyde, obtained from cyclization of the pendant CHO function, whereas species can be viewed as an ethanoyl-conjugated Ru-pyrrole. Derivatives - were characterized by single crystal X-ray diffraction, ESI-Ms, IR, and NMR spectroscopy, indicating distinct features for the Ru-bonded pyrrolyl groups. DFT computational results, coplanarity, bond equalization, and electron delocalization along the fused five-membered rings support aromatic features. In accordance with the antisymbiotic -influence, both the isolated isomers and disclose CO ligands opposite to N- or O-anionic groups. The quantitative Mayer bond order evidences a stabilizing backbonding effect. Antibacterial and antifungal trials on Gram-positive (), Gram-negative (), and Candida albicans were further carried out.