Phosphine Selenides Research Articles

Selenium Transfer from Secondary Phosphine Selenides to Aminoacetylenic Ketones: Access to 1,2-Dihydro-3H-pyrrole-3-selones with a Stable C═Se Bond.

Secondary phosphine selenides were found to react with γ-aminoacetylenic ketones (80-85 °C, MeCN, 17-40 h) to afford 1,2-dihydro-3H-pyrrole-3-selones in 48-80% yields, products of unprecedented selenium transfer from the P═Se bond to replace the carbonyl oxygen and to form dihydro-3H-pyrrole-3-selones having a C═Se bond stable under ambient conditions.

Unveiling the electronic structure peculiarities of phosphine selenides as NMR probes for non-covalent interactions: an experimental and theoretical study.

In this work, R3PSe (R = Me, Et, n-Bu, t-Bu and Ph) were studied experimentally using NMR spectroscopy in solution and the solid-state in combinaton with quantum chemical methods. The study shows that the NMR parameters of these phosphine selenides, such as δP, δSe, and 1JPSe, are sensitive to subtle changes in the electronic environment of the P and Se atoms. Consequently, phosphine selenides R3PSe can serve as promising spectral probes for the detection and quantitative investigation of various non-covalent interactions. Additionally, the variations of R in phosphine selenides influence the observed NMR spectral parameters, primarily through effects such as π-backdonation and hyperconjugation, which have been observed experimentally and confirmed theoretically.

Phosphine selenides: versatile NMR probes for analyzing hydrogen OH⋯Se and halogen I⋯Se bonds.

Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for studying the structure and dynamics of various non-covalent interactions. However, often spectral parameters that are applicable for estimation of parameters of one type of non-covalent interaction will be inapplicable for another. Therefore, researchers are compelled to use spectral parameters that are specifically tailored to the type of non-covalent interaction being studied. This complexity makes it difficult to compare different types of non-covalent interactions with each other and, consequently, to establish a strict unified classification for them. This pioneering study proposes to use phosphine selenides as universal probes for investigating hydrogen and halogen bonding in solution. The study was carried out using the example of triethylphosphine selenide Et3PSe complexes with hydrogen bonds of Se⋯HO type and R3PSe (where R: Me, Et, n-Bu, t-Bu and Ph) with halogen bonds of Se⋯X type (where X: I and Br) in solution. The presence of non-covalent interactions was confirmed experimentally by means of 1H, 31P and 77Se NMR, as well as by quantum chemical calculation methods (optimization: PW6B95-D3/def2-QZVP; NMR: B97-2/pcsSeg-2).

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.

Synthesis and coordination of a pair of isomeric ferrocene phosphinoamines

Ferrocene P,N-ligands have been extensively studied due to their favorable catalytic properties. This contribution focuses on a pair of new, isomeric ferrocene phosphinoamines, FcNHCH2CH2PPh2 (1) and FcN(Me)CH2PPh2 (2), which were prepared from aminoferrocene, converted to the respective phosphine selenides (1-Se and 2-Se) and further studied as ligands in Pd(II) complexes containing the 2-(dimethylamino-κN)phenyl-κC1 auxiliary (LNC) ligand. Thus, cleavage of the dimeric precursor [(LNC)Pd(μ-Cl)]2 with the phosphinoamines afforded the corresponding phosphine complexes [(LNC)PdCl(1-κP)] (5) and [(LNC)PdCl(2-κP)] (6) with trans-P,N configuration. The subsequent removal of the chloride ligand with AgClO4 from 5 produced the cationic bis-chelate complex [(LNC)PdCl(1-κ2P,N)]ClO4 (7), whereas an analogous reaction with 6 gave no defined product. The phosphinoamines and their complexes were characterized by elemental analysis and common spectroscopic methods, and the crystal structures of 1, 2, and 7 were determined by single-crystal X-ray diffraction analysis. A cyclic voltammetry study, supported by DFT calculations, revealed that the primary electrochemical oxidation of these compounds occurs at the ferrocene unit.

Reactivity Studies of Phosphinines: The Selenation of Diphenyl-Phosphine Substituents and Formation of a Chelating Bis(Phosphinine) Palladium(II) Complex

Phosphinines and donor-substituted phosphinines are of recent interest due to their use in homogeneous catalysis. In this article, a Pd(II) bis(phosphinine) complex was characterised and phosphorus–selenium coupling constants were used to assess the donor properties of the diphenylphosphine substituents of phosphinine ligands to promote their further use in catalysis. The selenation of 2,5-bis(diphenylphosphino)-3,6-dimethylphosphinine (5) and 2-diphenylphosphino-3-methyl-6-trimethylsilylphosphinine (6) gave the corresponding phosphine selenides 8 and 9, respectively, leaving the phosphinine ring intact. Multinuclear NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction confirmed the oxidation of all the diphenylphosphine substituents with 1JP-Se coupling constants determined to be similar to SePPh3, indicating that the phosphinine rings were electronically similar to phenyl substituents. Solutions of 6 were found to react with oxygen slowly to produce the phosphine oxide 10 along with other by-products. The reaction of [bis{3-methyl-6-(trimethylsilyl)phosphinine-2-yl}dimethylsilane] (4) with [PdCl2(COD)] gave the chelating dichloropalladium(II) complex, as determined by multinuclear NMR spectroscopy, mass spectrometry and an elemental analysis. The molecular structure of the intermediate 2 in the formation of 4,6-di(tert-butyl)-1,3,2-diazaphosphinine (3) was also determined, which confirmed the structure of the diazaphosphacycle P(Cl){N=C(tBu)CH=C(tBu)-N(H)}.

Diastereoconvergent synthesis of anti-1,2-amino alcohols with N-containing quaternary stereocenters via selenium-catalyzed intermolecular C-H amination.

We report a diastereoconvergent synthesis of anti-1,2-amino alcohols bearing N-containing quaternary stereocenters using an intermolecular direct C–H amination of homoallylic alcohol derivatives catalyzed by a phosphine selenide. Destruction of the allylic stereocenter during the selenium-catalyzed process allows selective formation of a single diastereomer of the product starting from any diastereomeric mixture of the starting homoallylic alcohol derivatives, eliminating the need for the often-challenging diastereoselective preparation of starting materials. Mechanistic studies show that the diastereoselectivity is controlled by a stereoelectronic effect (inside alkoxy effect) on the transition state of the final [2,3]-sigmatropic rearrangement, leading to the observed anti selectivity. The power of this protocol is further demonstrated on an extension to the synthesis of syn-1,4-amino alcohols from allylic alcohol derivatives, constituting a rare example of 1,4-stereoinduction.

Synthesis, structural, characterization and Hirshfeld analysis of a bisselenide and a zinc complex of a new hemilabile ferrocenylbisphosphane, [Fe{C5H4P(C6H4CH2NMe2-o)2}2

The novel hemilabile ferrocenylbisphosphane 1,1'-bis(bis{2-[(dimethylamino)methyl]phenyl}phosphanyl)ferrocene, [Fe{C5H4P(C6H4CH2NMe2-o)2}2] (1), was synthesized by reacting bis(dichlorophosphanyl)ferrocene, [Fe{C5H4(PCl2)}2] with LiC6H4CH2NMe2-o. Treatment of 1 with gray selenium and anhydrous ZnCl2 yielded, respectively, the bisselenide (ferrocene-1,1'-diyl)bis(bis{2-[(dimethylamino)methyl]phenyl}phosphine selenide), [Fe(C23H28N2PSe)2] (2), and the dizinc complex [μ-1,1'-bis(bis{2-[(dimethylamino)methyl]phenyl}phosphanyl)ferrocene-κ2N,P:κ2N',P']bis[dichloridozinc(II)] dichloromethane monosolvate, [FeZn2Cl4(C23H28N2P)2]·CH2Cl2 (3), and both have been structurally characterized. Both compounds crystallized with the asymmetric unit containing half a molecule and with the Fe atom on an inversion centre. A Hirshfeld surface analysis indicated that the most significant contributions to the crystal packing of 2 are from H...H (76.7%), C...H/H...C (13.2%) and Se...H/H...Se (7.1%) contacts, while those for 3 are from H...H (62.3%), Cl...H/H...Cl (24.4%) and C...H/H...C (10.9%) contacts.

Carbonyl Compounds: Reactants, Catalysts and Products

Ultra-branched mixed tetradentate tripodal phosphines and phosphine chalcogenides have been synthesized by the exhaustive regioselective addition of secondary phosphines, phosphine sulfides and phosphine selenides to available tris(4-vinylbenzyl)phosphine oxide under free-radical conditions (UV irradiation or AIBN) in good to excellent yields.

Quantum Chemical Study of the Addition of Secondary Phosphine Chalcogenides to Vinyl Selenides

DFT quantum chemical calculations at the B3PW91/6-31G(d) level of theory have shown that the addition of secondary phosphine sulfides and phosphine selenides with alkyl, phenyl, and phenylalkyl substituents to pentyl vinyl and hexyl vinyl selenides follows a molecular mechanism against the Markovnikov rule through energetically favorable eight-membered transition state, leading to the formation of tertiary phosphine chalcogenides. Secondary phosphine selenides are more reactive than the corresponding phosphine sulfides.

Correlated ab initio calculations of one-bond 31 P77 Se and 31 P125 Te spin-spin coupling constants in a series of PSe and PTe systems accounting for relativistic effects (part 2).

Synthetic chalcogen-phosphorus chemistry permanently makes new challenges to computational Nuclear Magnetic Resonance (NMR) spectroscopy, which has proven to be a powerful tool of structural analysis of chalcogen-phosphorus compounds. This paper reports on the calculations of one-bond 31 P77 Se and 31 P125 Te NMR spin-spin coupling constants (SSCCs) in the series of phosphine selenides and tellurides. The applicability of the combined computational approach to the one-bond 31 P77 Se and 31 P125 Te SSCCs, incorporating the composite nonrelativistic scheme, built of high-accuracy correlated SOPPA (CC2) and Coupled Cluster Single and Double (CCSD) methods and the Density Functional Theory (DFT) relativistic corrections (four-component level), was examined against the experiment and another scheme based on the four-component relativistic DFT method. A special J-oriented basis set (acv3z-J) for selenium and tellurium atoms, developed previously by the authors, was used throughout the NMR calculations in this work at the first time. The proposed computational methodologies (combined and 'pure') provided a reasonable accuracy for 31 P77 Se and 31 P125 Te SSCCs against experimental data, characterizing by the mean absolute percentage errors of about 4% and 1%, and 12% and 8% for selenium and tellurium species, respectively. The present study reports typical relativistic corrections to 77 Se31 P and 125 Te31 P SSCCs, calculated within the four-component DFT formalism for a broad series of tertiary phosphine selenides and tellurides with different substituents at phosphorus.

Oxidative Cross-Coupling of Cysteamine with Secondary Phosphine Chalcogenides: Aspects of Reaction Chemoselectivity

Cysteamine (2-aminoethanethiol) undergoes oxidative cross-coupling with secondary phosphine sulfides and phosphine selenides under mild conditions (room temperature, 2–5 h, CCl4/Et3N) to give products of monocoupling at the amino group (ethylchalcogenophosphinic amides with free SH functions) and dicoupling (l-chalcogenophosphorylamino-2-chalcogenothioethanes) in 72–85% total yield. Under similar conditions, stirring an equimolar mixture of bis(2-phenylethyl)phosphine sulfide (or selenide), 1-butylamine, and 1-butanethiol leads to the chemoselective formation of the corresponding chalcogenophosphinic amides in high yield.

Molecular and crystal structures of tris(3-methylphenyl)phosphine and its chalcogenides

The molecular and crystal structures of tris(3-methylphenyl)phosphine, tris(3-methylphenyl)phosphine oxide, tris(3-methylphenyl)phosphine sulfide and tris(3-methylphenyl)phosphine selenide were determined by X-ray diffraction. It was previously indicated that phosphine oxide should be isostructural with phosphine sulfide and phosphine selenide. However, this statement was not confirmed experimentally: the geometrical structure of the phosphine oxide is closer to the geometry of the phosphine. Tris(3-methylphenyl)phosphine, tris(3-methylphenyl)phosphine sulfide and tris(3-methylphenyl)phosphine selenide crystallize in the orthorhombic space group Pbca, while the phosphine oxide molecules in the crystal are packaged in the space group Pca21 with screw axis.

Evaluating stereoelectronic properties of bulky dialkylterphenyl phosphine ligands

The stereoelectronic properties of a series of sterically hindered phosphines containing a terphenyl substituent, PR2Ar’ (R = alkyl; Ar’ = C6H3-2,6-Ar2), have been evaluated by various methods. Their σ-donating capacity has been assessed on the basis of the carbon monoxide stretching frequencies in benchmark iridium [IrCl(CO)2(PR2Ar’)] and rhodium [Rh(acac)(CO)2(PR2Ar’)] (acac = acetylacetonate) complexes, as well as by measuring 31P–77Se scalar coupling constants (1JSeP) for the corresponding phosphine selenides (Se=PR2Ar’). In turn, the steric profile of terphenyl phosphines has been gauged by calculating Tolman Cone Angle (TCA), ligand shielding (G) and percent buried volume (%VBur) parameters. These calculations have been carried out from both X-ray diffraction and DFT-optimized structures. We have also examined several of the widely used biaryl phosphines for comparative purposes.

Versatile coordination and C-H activation of a multi-donor phosphinoferrocene carboxamide ligand in Pd(ii) complexes.

A multi-donor phosphinoferrocene carboxamide, FcCONHCH2CH2PPh2 (1, Fc = ferrocenyl), was prepared, converted into the corresponding phosphine oxide 1O and phosphine selenide 1Se and, mainly, studied as a ligand in Pd(ii) complexes. In its native form, amide 1 preferentially coordinated soft Pd(ii) as a simple phosphine, giving rise to mixtures of cis and trans-[PdX2(1-κP)2] (2; X = Cl (a), Br (b), and I (c)), wherein the isomer ratios depended on the auxiliary halide ligand or, alternatively, to the complex [(LNC)PdCl(1-κP)] (6, LNC = 2-[(dimethylamino)methyl-κN]phenyl-κC1). This coordination mode was nevertheless easily changed when creating a vacant coordination site at the palladium. Thus, treatment of 2a with NH4[PF6] in the presence of free 1 produced [PdCl(1-κP)3][PF6] (3), while complete halogen removal with a Ag(i) salt led to cationic complexes cis-[Pd(1-κ2O,P)2]X2 (4, X = CF3SO3 (a), ClO4 (b), BF4 (c)) or [(LNC)Pd(1-κ2O,P)]X (7a and 7b), containing seven-membered O,P-chelate rings. In contrast, amide nitrogen deprotonation with KOt-Bu followed by spontaneous intramolecular halogen substitution resulted in the transformation of 6 into the chelate complex [(LNC)Pd{(1- H)-κ2N,P}] (8) featuring a five-membered N,P-chelate ring, and in the conversion of 2a and 2b into the product of C-H bond activation [Pd{Fe(η5-C5H3CONCH2CH2PPh2-κ3C,N,P)(η5-C5H5)}(1-κP)] (5), with doubly chelating deprotonated 1. Importantly, complexes 2-4-5 and 6-7-8 were mutually interconverted in triads (by protonation/deprotonation and by halide addition/abstraction), which highlights the flexible coordination and chemical stability of ligand 1. The crystal structures of 1O·½H2O, trans-2a·MeCN, trans-2b·3C2H4Cl2, trans-2c·2.5C2H4Cl2, 4a·CH2Cl2, 5·3CHCl3·Et2O, and 8 were determined by single-crystal X-ray diffraction analysis, and the representative compounds were studied by cyclic voltammetry.

Regioselective Metal-Free Aza-Heck Reactions of Terminal Alkenes Catalyzed by Phosphine Selenides.

Phosphine selenides are introduced as an alternate class of selenium-based catalysts for the aza-Heck reaction of alkenes. Using these catalysts, a range of terminal alkenes react with NFBS to give oxidative amination products. Judicious choice of phosphine ligand gives greater regio- and stereoselectivity than with diphenyl diselenide, enabling the selective formation of E terminal enimides in high yields. Isotope-labeling experiments and measurements of kinetic isotope effects reveal that the reaction occurs stereospecifically via irreversible anti addition, followed by rate-determining syn elimination.

Synthesis, Properties, and Catalytic Application of a Triptycene-Type Borate-Phosphine Ligand

A borate-containing caged triarylphosphine L-X (X = Na or NBu4), featuring a 9-phospha-10-boratriptycene framework, was synthesized and characterized by NMR spectroscopy and X-ray diffraction analysis. The NMR coupling constant of the corresponding phosphine selenide indicated a higher electron-donating property of the borate-phosphine L compared to that of the 9-phospha-10-silatriptycene derivative (Ph-TRIP). The coordination property of L-X to [PdCl(η3-allyl)]2 was dependent on the countercation, giving a neutral Pd complex [PdCl(η3-allyl)(L-NBu4)] from L-NBu4 in CH2Cl2 or a zwitterionic Pd complex [Pd(η3-allyl)(MeCN)(L)] from L-Na in MeCN/CH2Cl2. Utility of L-X as a ligand for metal catalysis was demonstrated in the Pd-catalyzed Suzuki–Miyaura cross-coupling of aryl chlorides.

Comparing the asymmetric dppf-type ligands with their semi-homologous counterparts

Two series of asymmetric ferrocene diphosphines, namely the dppf-type ligands R2PfcPPh2 (protected as BH3 adducts; fc = ferrocene-1,1′-diyl) and their semi-homologous counterparts R2PfcCH2PPh2 (both in free and BH3-protected form), with diverse PR2 groups (R = cyclohexyl, isopropyl and tert-butyl), were prepared and further converted into the respective phosphine selenides, R2P(Se)fcP(Se)Ph2 and R2P(Se)fcCH2P(Se)Ph2, which were in turn used to evaluate the electronic properties of these diphosphines through 1JSeP coupling constants. When reacted with [PdCl2(MeCN)2] or [PdCl2(cod)] (cod = cycloocta-1,5-diene), the dppf-type ligands exclusively afforded the chelate complexes [PdCl2(R2PfcPPh2-κ2P,P′)], whereas the more flexible, homologous ligands produced mixtures mainly containing the similar chelate complexes [PdCl2(R2PfcCH2PPh2-κ2P,P′)] and the P,P′-bridged dimers [PdCl2(μ(P,P′)-R2PfcCH2PPh2)]2.

Synthesis, crystal structures and magnetic properties of two iron (II) tris(pyridyl)phosphine selenides complexes

ABSTRACTWe reported the synthesis of tris(pyridyl)phosphine selenide (TppSe) and tris(4-methylpyridin-2-yl)phosphine selenide (MeTppSe), which were prepared by a simple and straightforward one-pot method with red phosphorus in a KOH/DMSO suspension, and treatment of resulted phosphines with selenium in hot toluene. These compounds were characterized by mass spectroscopy, 1H, 13C and 31P NMR spectroscopies and the structure of MeTppSe was characterised by a single-crystal X-ray diffraction. Furthermore, The reactions of selenides with Fe(ClO4)2·6H2O afforded two new iron(II) mononuclear metal complexes [Fe(TppSe)2][ClO4]2·3DMF (1) and [Fe(MeTppSe)2][ClO4]2·2DMF (2). Detailed structural analyses and magnetic susceptibility measurements confirm no spin transition from low-spin to the high-spin state between 2 and 300 K in two iron(II) complexes.

Unexpected Carbon–Selenium Bond Formation in the Reaction of Secondary Phosphine Selenides with Benzoylphenylacetylene

Secondary phosphine selenides reacted as selenating agents with benzoylphenylacetylene in wet acetonitrile (70–72°C) to give bis(2-benzoyl-1-phenylvinyl) selenide in up to 43% yield.