Expedient one-pot organometallics-free synthesis of tris(2-pyridyl)phosphine from 2-bromopyridine and elemental phosphorus

Phosphine chalcogenides and their derivatives from red phosphorus and functionalized pyridines, imidazoles, pyrazoles and their antimicrobial and cytostatic activity

Tertiary phosphine oxides, phosphine sulfides, and phosphine selenides containing pyridine, imidazole, and pyrazole groups have been synthesized via the reaction of elemental phosphorus or secondary phosphine oxides with functional pyridines, imidazoles, and pyrazoles. Alkyl tris(2-pyridylethyl)phosphonium iodide and bromide are also obtained by quaternization of the corresponding phosphine. Antimicrobial activity of the synthesized compounds, including nitrogen-containing heterocycles, phosphorus, selenium, and sulfur, with respect to Enterococcus durans, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa microorganisms is evaluated. It is found that phosphine chalcogenides bearing imidazole (14, 19), pyrazole (13), and pyridine fragments (5, 9) and phosphonium salts (11, 12) can be considered as new promising antibacterial agents. For some synthesized compounds, LC₅₀ is determined. Phosphine oxide with methylpyrazole fragments (13) and phosphonium salts (11, 12) show strong profile of antimicrobial activity, and cytotoxic effect of phosphonium bromide having a long chain radical (12) is by order of magnitude higher than that of cisplatin. We believe that the results obtained may contribute to the development of highly effective agents for the treatment and prevention of bacterial infections and cancers.

Luminescence behaviour of Au(I)-Cu(I) heterobimetallic coordination polymers based on alkynyl-tris(2-pyridyl)phosphine Au(I) complexes

A set of alkynyl-tris(2-pyridyl)phosphine Au(i) complexes was synthesized and characterized. Free coordination functions on the ligand environment periphery, namely 'scorpionate' PPy3 and the C[triple bond, length as m-dash]C bond, allowed these ditopic metalloligands to be selectively linked to 1D coordination polymers by reaction with Cu(i), which used both Cu-(N-PPy3) and Cu-(η2-C[triple bond, length as m-dash]C) coordination modes. Single-crystal and powder XRD, NMR, and XPS techniques were used to characterize the coordination polymers obtained. Heterobimetallic Au(i)-Cu(i) coordination polymers demonstrate triplet photoluminescence which was studied by spectroscopic and computational methods to understand the pathway of energy transfer inside the chain of linked chromophore centres. The intriguing feature of the electronic structure of heterobimetallic supramolecular assemblies is the 'long-distance' electronic transition involving PhC2 and PPy3 ligands located at a distance of more than 1 nm from each other. Thus, the assembly of a heterobimetallic coordination polymer from relatively simple 'building blocks' retains the block-wise nature of the electronic structure, but the photophysical properties of the polymer are fundamentally different from the properties of discrete organometallic components.

Architecture and synthesis of P,N-heterocyclic phosphine ligands

Diverse P,N-phosphine ligands reported to date have performed exceptionally well as auxiliary ligands in organometallic catalysis. Phosphines bearing 2-pyridyl moieties prominently feature in literature as compared to phosphines with five-membered N-heterocycles. This discussion seeks to paint a broad picture and consolidate different synthetic protocols and techniques for N-heterocyclic phosphine motifs. The introduction provides an account of P,N-phosphine ligands, and their structural and coordination benefits from combining heteroatoms with different basicity in one ligand. The body discusses the synthetic protocols which focus on P–C, P–N-bond formation, substrate and nucleophile types and different N-heterocycle construction strategies. Selected references are given in relation to the applications of the ligands.

Organophosphorus chemistry based on elemental phosphorus: advances and horizons

The results of studies on the application of elemental phosphorus for the synthesis of important organophosphorus compounds are surveyed and summarized. Currently, this trend represents a synthetically, environmentally and technologically attractive alternative to classical organophosphorus chemistry based on toxic and corrosive phosphorus chlorides. Direct phosphination and phosphinylation of organic compounds with elemental phosphorus (discussed in the first part of the review) basically extend the range of available phosphines, phosphine chalcogenides and phosphinic acids and provides further development of their synthetic potential (discussed in the second part of the review). It is shown that the breakthrough in this area is largely due to the discovery of reactions of elemental phosphorus (white and red) with various electrophiles in superbasic suspensions and emulsions derived from alkali metal hydroxides and to the development of electrochemical, electrocatalytic and catalytic activation of white phosphorus.

The bibliography includes 299 references.

Variable coordination of tris(2-pyridyl)phosphine and its oxide toward M(hfac)2: a metal-specifiable switching between the formation of mono- and bis-scorpionate complexes

An unexpected substitution of the anionic chelating ligands at the M^II centre by a neutral tripodal ligand has been observed in the reaction of Mn^II, Co^II, Ni^II and Cu^II hexafluoroacetylacetonates (hfac) with tris(2-pyridyl)phosphine (Py₃P) or its oxide (Py₃P = O). The nature of the metal ion in M(hfac)₂ and the M/L ratio determine the degree of substitution of hfac-anions (partial vs. total) and therefore, the structure of the complex formed (scorpionate vs. bis-scorpionate ones, respectively). Hence, the reaction of the ligands with [Cu(hfac)₂(H₂O)₂] in an equimolar ratio affords scorpionate [Cu(N,N',N''-Py₃P = X)(O,O'-hfac)(O-hfac)], wherein one hfac-ligand chelates metal, while the other hfac acts as an O-monodentate one. Using the two equivalents of Py₃P in this reaction leads to [Cu(N,N',N''-Py₃P)₂](hfac)₂, which contains a bis-scorpionate cation [Cu(Py₃P)₂]²⁺ and two noncoordinated hfac-anions. [Co(hfac)₂(H₂O)₂] and [Ni(hfac)₂(H₂O)₂], regardless of the M/L molar ratio, react with Py₃P = O to give cationic scorpionates [M(N,N',N''-Py₃P = O)(O,O'-hfac)(H₂O)](hfac), in which one hfac-anion is noncoordinated. In contrast, [Mn(hfac)₂(H₂O)₂], on interaction with Py₃P, results in the cationic complex [Mn(N,N',N''-Py₃P)₂][Mn(hfac)₃]₂ bearing a bis-scorpionate cation [Mn(Py₃P)₂]²⁺ and two [Mn(hfac)₃]₂^- counterions. The synthesized scorpionates have been characterized by X-ray diffractometry, cyclic voltammetry, SQUID magnetometry, FT-IR and UV-Vis techniques.

Multidentate 2-pyridyl-phosphine ligands – towards ligand tuning and chirality

The incorporation of a variety of alcohols into (amino)pyridyl-phosphine frameworks provides access to a library of multidentate (alkoxy)pyridyl-phosphines. Their coordination chemistry with Cu^I is explored.

Tris(2-pyridyl)phosphine as a versatile ligand for pnictogen acceptors

We report cationic complexes of arsenic and antimony with the tris(2-pyridyl)phosphine ligand. Chloride ion abstraction from the main group halide using TMSOTf in presence of the ligand gives [P(Pyr)₃Pn][OTf]₃, in which the trication adopts a Janus Head type complex with a C_3v symmetric cage structure and two apical lone pairs.

Transition metal complexes of the pyridylphosphine ligand o-C6H4(CH2PPy2)2

The synthesis and coordination behaviour of the pyridylphosphine ligand o-C₆H₄(CH₂PPy₂)₂ (Py = 2-pyridyl) are reported. The phosphine selenide was synthesised and the ¹J_PSe value of 738 Hz indicates the phosphorus atoms have a similar basicity to PPh₃. The ligand reacts with platinum(ii) and palladium(ii) complexes to give simple diphosphine complexes of the type [MX₂(PP)] (M = Pt, X = Cl, I, Me, Et; M = Pd, X = Cl, Me). When the ligand is reacted with chloromethyl(hexa-1,5-diene)platinum the [PtClMe(PP)] complex results, from which a series of unsymmetrical platinum complexes of the type [PtMeL(PP)]⁺ (L = PPh₃, PTA, SEt₂ and pyridine) can be made. This enabled the comparison of the cis and trans influences of a range of ligands. The following cis influence series was compiled based on ³¹P NMR data of these complexes: Py ≈ Cl > SEt₂ > PTA > PPh₃. Reaction of [PtClMe(PP)] with NaCH(SO₂CF₃)₂ and carbon monoxide slowly formed an acyl complex, where the CO had inserted in the Pt-Me bond. Attempts to achieve P,P,N chelation, through abstracting the chloride ligand in [PtClMe(PP)], were unsuccessful. When the ligand reacted with platinum(0), palladium(0) and silver(i) complexes the bis-chelated complexes [M(PP)₂] (M = Pt, Pd) and [Ag(PP)₂]⁺ were formed respectively. Reaction of the ligand with [Ir(COD)(μ-Cl)]₂ formed [IrCl(PP)(COD)]. When the chloride ligand was abstracted, the pyridyl nitrogens were able to interact with the iridium centre facilitating the isomerisation of the 1,2,5,6-η⁴-COD ligand to a 1-κ-4,5,6-η³-C₈H₁₂ ligand. The X-ray crystal structure of [Ir(1-κ-4,5,6-η³-C₈H₁₂)(PPN)]BPh₄ confirmed the P,P,N chelation mode of the ligand. In solution, this complex displayed hemilabile behaviour, with the pyridyl nitrogens exchanging at a rate faster than the NMR time scale at room temperature.

Luminescent CuI thiocyanate complexes based on tris(2-pyridyl)phosphine and its oxide: from mono-, di- and trinuclear species to coordination polymers

The synthesis, structural and photophysical properties of the novel family of Cu(i) thiocyanate complexes supported by tripodal ligands are presented.

Rapid water oxidation electrocatalysis by a ruthenium complex of the tripodal ligand tris(2-pyridyl)phosphine oxide

The tris(2-pyridyl)phosphine oxide (Py₃PO) complex [Ru(Py₃PO)(bpy)(OH₂)]²⁺ (bpy is 2,2'-bipyridine) is a pH-dependent water oxidation electrocatalyst that accelerates dramatically with increasing pH-up to 780 s^-1 at pH 10 (∼1 V overpotential). Despite retaining the pentakis(pyridine) ligand arrangement common to previously reported catalysts, the tripodal Py₃PO ligand framework supports much faster electrocatalysis. The early stages of the catalytic cycle are proposed to follow the typical pattern of single-site ruthenium catalysts, with two sequential 1H⁺/1e^- proton-coupled electron transfer (PCET) oxidations, but the pH-dependent onset of catalysis and rapid rates are distinguishing features of the present system.