Antonella Guerriero

Facile heterogeneous catalytic hydrogenations of CN and CO bonds in neat water: anchoring of water-soluble metal complexes onto ion-exchange resins

Rare examples are known of non-covalent immobilization of water-soluble transition metal complexes onto solid supports and their application in catalytic hydrogenations in neat water. In the present work we report on the synthesis of a novel Ir(I) complex bearing the water soluble monodentate cage phosphine PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) and its immobilisation onto commercial ion-exchange resins by a straightforward heterogenization method. The materials obtained were used as catalysts for the hydrogenations of cyclic imines and α-keto esters under mild conditions using water as a green reaction medium, avoiding as much as possible the use of toxic and/or hazardous solvents.

Supramolecularly controlled surface activity of an amphiphilic ligand. Application to aqueous biphasic hydroformylation of higher olefins

A biphasic catalytic system has been elaborated in which the amphiphilic species concentrations at the aqueous/organic interface could be thermocontrolled by the supramolecular interaction between β-cyclodextrins and the 1-(4-tert-butyl)benzyl-1-azonia-3,5-diaza-7-phosphaadamantyl ligand (1). The system proved efficient in Rh-catalyzed hydroformylations of higher olefins. An increase in the catalytic activity was observed without alteration in either the chemo- or the regio-selectivity. The main advantage of the cyclodextrin/1 couple lies in the rapid decantation of the biphasic system at the end of the reaction. This study represents the first example of thermoregulation of the surface activity of an amphiphilic phosphane by a cyclodextrin.

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.

Water-Soluble, 1,3,5-Triaza-7-phosphaadamantane-Stabilized Palladium Nanoparticles and their Application in Biphasic Catalytic Hydrogenations at Room Temperature

Water‐dispersible Pd nanoparticles stabilized by the hydrophilic cage‐like aminophosphine ligand 1,3,5‐triaza‐7‐phosphaadamantane and its N‐methyl derivative were synthesized and fully characterized in the colloidal state by TEM, and NMR and UV spectroscopy and in the solid state by X‐ray photoelectron spectroscopy and powder XRD. The three different nanoparticles obtained showed a narrow distribution range with average core sizes of 2.8, 3.2, and 3.5 nm. The activity of some of these Pd nanoparticles as catalysts in the biphasic hydrogenation of organic substrates under mild conditions has been tested, and good results and excellent reusability (up to nine catalytic runs) were obtained.

Lower- and upper-rim-modified derivatives of 1,3,5-triaza-7-phosphaadamantane: Coordination chemistry and applications in catalytic reactions in water

In this article, a brief review of the recent functionalizations of the cage-like water-soluble phosphine 1,3,5-triaza-7-phosphaadamantane (PTA), involving N-quaternization (lower rim) and introduction of a side arm in C-6 position (upper rim) will be presented, highlighting selected examples in their use as ligands for ruthenium(II), iridium(I), and rhodium(I) moieties together with applications of the related complexes in homogeneous catalysis.

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.

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.

Hydrogen Activation in Water by Organometallic Complexes

Hydrogen has found important applications as reducing agent for chemical transformations and is nowadays considered as one of the most promising energy vectors able to fuel devices to produce electricity on demand (direct hydrogen fuel cells). Crucial to its application is the understanding at the molecular level of how hydrogen interacts with (transition) metals which are commonly used as catalysts to lower the energy barrier to split the H2 molecule into its components and allow transfer and reactivity. In this chapter, selected examples of hydrogen activation by water-soluble organometallic complexes are summarized.

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.