Convenient synthesis of the water-soluble ligand hexasodium Tris(4-phosphonatophenyl)phosphine

Covalent Modification of Nucleobases using Water-Soluble Palladium Catalysts

Nucleosides represent one of the key building blocks of biochemistry. There is significant interest in the synthesis of nucleoside-derived materials for applications as probes, biochemical models, and pharmaceuticals. Palladium-catalyzed cross-coupling reactions are effective methods for making covalent modification of carbon and nitrogen sites on nucleobases under mild conditions. Water-soluble catalysts derived from palladium and hydrophilic ligands, such as tris(3-sulfonatophenyl)phosphine trisodium (TPPTS), are efficient catalysts for a range of coupling reactions of unprotected halonucleosides. Over the past two decades, these methods have been extended to direct functionalization of halonucleotides, as well as RNA and DNA oligonucleotides (ONs) containing halogenated bases. These methods can be run under biocompatible conditions, including examples of Suzuki coupling of modified DNA in whole cells and tissue samples. In this account, development of this methodology by our group and others is highlighted along with the extension of these catalyst systems to modification of nucleotides and ONs.

Synthesis of Hydrophilic Phosphorus Ligands and Their Application in Aqueous-Phase Metal-Catalyzed Reactions

Transition metal-catalyzed reactions in aqueous media are experiencing a constant increase in interest. In homogenous catalysis the use of water as a solvent offers advantages in cost, safety, the possibility of two-phase catalysis and simplified separation strategies. In the life sciences, transition metal catalysis in aqueous systems enables the ligation or modification of biopolymers in buffer systems or even in their cellular environment. In biocatalysis, aqueous systems allow the simultaneous use of enzymes and transition metal catalysts in cascade reactions. The use of water-soluble phosphine ligands still represents the most reliable and popular strategy for transferring metal catalysts into the aqueous phase. This review summarizes the recent advancements in this field since 2009 and describes current synthetic strategies for the preparation of hydrophilic phosphines and phosphites. In addition, recent applications of transition metal catalysis in aqueous solvents using these hydrophilic ligands are presented.

Phosphonic acid: preparation and applications

The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. These applications are covering a large panel of research fields including chemistry, biology and physics thus making the synthesis of phosphonic acids a determinant question for numerous research projects. This review gives, first, an overview of the different fields of application of phosphonic acids that are illustrated with studies mainly selected over the last 20 years. Further, this review reports the different methods that can be used for the synthesis of phosphonic acids from dialkyl or diaryl phosphonate, from dichlorophosphine or dichlorophosphine oxide, from phosphonodiamide, or by oxidation of phosphinic acid. Direct methods that make use of phosphorous acid (H3PO3) and that produce a phosphonic acid functional group simultaneously to the formation of the P-C bond, are also surveyed. Among all these methods, the dealkylation of dialkyl phosphonates under either acidic conditions (HCl) or using the McKenna procedure (a two-step reaction that makes use of bromotrimethylsilane followed by methanolysis) constitute the best methods to prepare phosphonic acids.

Tris(3-aminophenyl)phosphine oxide ethanol solvate

The title compound crystallized as an ethanol solvate, C₁₈H₁₈N₃OP·C₂H₆O. It is the reduction product of tris­(3-nitro­phen­yl)phosphine oxide. In the crystal, there are inter­molecular N—H⋯O hydrogen bonds between neighbouring tris­(3-amino­phen­yl)phosphine oxide mol­ecules and O—H⋯O hydrogen bonds involving the ethanol solvent mol­ecule.

Organometallic catalysts in synthetic organic chemistry: From reactions in aqueous media to gold catalysis

Water has attracted significant attention as an alternative solvent for transition-metal-catalyzed reactions. The use of water as solvent allows simplified procedures for separation of the catalyst from the products and recycling of the catalyst. Water is an inexpensive reagent for the formation of oxygen-containing products such as alcohols. The use of water as a medium for promoting organometallic and organic reactions is also of great potential. This chapter will focus on old and recent developments in the design and applications of some catalytic reactions using aqueous-phase Pd, Rh, Pt, and Au complexes.

Triarylphosphine-Stabilized Platinum Nanoparticles in Three-Dimensional Nanostructured Films as Active Electrocatalysts

Ligand-stabilized platinum nanoparticles (Pt NPs) can be used to build well-defined three-dimensional (3-D) nanostructured electrodes for better control of the catalyst architecture in proton exchange membrane fuel cells (PEMFCs). Platinum NPs of 1.7 +/- 0.5 nm diameter stabilized by the water-soluble phosphine ligand, tris(4-phosphonatophenyl)phosphine (TPPTP, P(4-C6H4PO3H2)3), were prepared by ethylene glycol reduction of chloroplatinic acid and subsequent treatment of the isolated nanoparticles with TPPTP. The isolated TPPTP-stabilized Pt NPs were characterized by multinuclear magnetic resonance spectroscopy (31P and 195Pt NMR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS). The negatively charged TPPTP-Pt NPs were electrostatically deposited onto a glassy carbon electrode (GCE) modified with protonated 4-aminophenyl functional groups (APh). Multilayers were assembled via electrostatic layer-by-layer deposition with cationic poly(allylamine HCl) (PAH). These multilayer films are active for the key hydrogen fuel cell reactions, hydrogen oxidation (anode) and oxygen reduction (cathode). Using a rotating disk electrode configuration, fully mass-transport limited kinetics for hydrogen oxidation was obtained after 3 layers of TPPTP-Pt NPs with a total Pt loading of 4.2 microg/cm2. Complete reduction of oxygen by four electrons was achieved with 4 layers of TPPTP-Pt NPs and a total Pt loading of 5.6 microg/cm2. A maximum current density for oxygen reduction was reached with these films after 5 layers resulting in a mass-specific activity, i(m), of 0.11 A/mg(Pt) at 0.9 V. These films feature a high electrocatalytic activity and can be used to create systematic changes in the catalyst chemistry and architecture to provide insight for building better electrocatalysts.

Coordination chemistry of the water-soluble ligand TPPTP and formation of a [Mo(CO)5(m-TPPTP)] monolayer on an alumina surface

Phosphonate and phosphonic acid functionalized phosphine complexes of platinum(II) were prepared via direct reaction of the ligands with K2PtCl4 in water. Either cis or trans geometries were found depending on the nature of the ligand. The crystal structure of P(3-C6H4PO3H2)3.2H2O (6b) (triclinic, P1, a = 8.3501(6) A, b = 10.1907(6) A, c = 14.6529(14) A, alpha = 94.177(6) degrees, beta = 105.885(6) degrees, gamma = 108.784(5) degrees, Z = 2) shows a layered arrangement of the phosphonic acid. The phosphonodiamide complex cis-[PtCl2(P[4-C6H4PO[N(CH3]2]]3)2].3H2O (10) was synthesized in 89% yield and hydrolyzed to the phosphonic acid complex using dilute HCl. Aqueous phase and silica gel supported catalytic phosphonylation of phenyl triflate using palladium phosphine complexes was achieved. A molybdenum complex, Mo(CO)5[P3-C6H4PO3H2)3] (11), was synthesized in situ and grafted to an alumina surface. XPS, RBS, and AFM studies confirm the formation of a monolayer of 11 on the alumina surface.

Synthesis of a new water-soluble C(2)-symmetric chiral diamine: preliminary investigation of its catalytic properties for asymmetric hydrogenation under biphasic conditions

A water-soluble version of N,N'-dimethyl-1,2-diphenylethane-1,2-diamine was prepared by introduction of phosphonic acid moieties on the para position of the aromatic rings. Preliminary investigation of the catalytic properties of the iridium complex of this ligand under biphasic conditions showed that this system compared well with the homogeneous counterpart for the asymmetric hydrogenation of ketones but with noticeably higher reaction rates for the biphasic system.