Water-Soluble Silver(I) Complexes Featuring the Hemilabile 3,7-Dimethyl-1,3,5-triaza-7-phosphabicyclo[3.3.1]nonane Ligand: Synthesis, Characterization, and Antimicrobial Activity.

This paper describes the preparation and comprehensive characterization of a series of water-soluble cationic silver(I)-centered complexes featuring the hemilabile P, N-ligand known as 3,7-dimethyl-1,3,5-triaza-7-phosphabicyclo[3.3.1]nonane (herein abbreviated as PTN(Me)) and differing types of monoanionic counterions including known biologically active sulfadiazine and triclosan. The complexes primarily differed though the number of coordinating PTN(Me) ligands. The bis-substituted Ag(I) complexes revealed P, N bidentate coordination, while the only P-monocoordination of the metal center was observed for the tris-substituted systems. The bis-ligated silver compounds were observed to quickly degrade upon photoexposure or in contact with air. In contrast, the tris-ligated complexes demonstrated greater stability, in particular, a high resistance to photo-decomposition. Calculated geometry optimized models using the density functional theory method (BP86) revealed for the bis-substituted PTN(Me) Ag(I) species that the total enthalpy of the tetrahedral C2-symmetric structure is marginally lower by -0.6 kcal mol-1 compared to the planar C2 h structure, which is analogous for the corresponding [Au(PTN(Me))2]+ complex with Δ H = -0.5 kcal mol-1. Hence both types of complexes feature free rotation of the PTN ligand about the M-P bond axis. This series of Ag(I) and bis-PTN(Me) Au(I) complexes were evaluated using the agar well diffusion test for potential antimicrobial and antifungal activity. The nature of the counterion was found to have a strong correlation with the area of microbiological growth inhibition. Silver(I) complexes bearing the deprotonated triclosan as the counterion demonstrated the greatest activity, with large zones of growth inhibition, with the tris-ligated triclosan complex obtaining of a high clearance of 42 mm against the Gram-negative Escherichia coli. In contrast, the previously reported [Au(PTN(Me))2]Cl complex demonstrated activity only against E. coli, which is lower than that observed for the silver(I) PTN(Me) species.

New Class of Half-Sandwich Ruthenium(II) Arene Complexes Bearing the Water-Soluble CAP Ligand as an in Vitro Anticancer Agent.

Ruthenium(II) arene complexes of 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP) were obtained. Cytotoxicity studies against cancer cell lines reveal higher activity than the corresponding PTA analogues and, in comparison to the effects on noncancerous cells, the complexes are endowed with a reasonable degree of cancer cell selectivity.

New Wind in Old Sails: Novel Applications of Triphos-based Transition Metal Complexes as Homogeneous Catalysts for Small Molecules and Renewables Activation.

Recent developments in the coordination chemistry and applications of Ru-triphos [triphos = 1,1,1-tris-(diphenylphosphinomethyl)ethane] systems are reviewed, highlighting their role as active and selective homogenous catalysts for small molecule activation, biomass conversions and in carbon dioxide utilization-related processes.

The role of metals and ligands in organic hydroformylation.

In this chapter the effect of transition metals and of ancillary stabilizing ligands on the activity, regioselectivity, and chemoselectivity in hydroformylation reactions applied to organic synthesis will be reviewed, highlighting recent cases of particular interest, including examples of both homogeneous and heterogeneous catalytic reactions.