The coordination chemistry of dithiophosphonates: An emerging and versatile ligand class

Dithiophosphonate-Protected Eight-Electron Superatomic Ag21 Nanocluster: Synthesis, Isomerism, Luminescence, and Catalytic Activity

The structure-property relationship considering isomerism-tuned photoluminescence and efficient catalytic activity of silver nanoclusters (NCs) is exclusive. Asymmetrical dithiophosphonate NH4[S2P(OR)(p-C6H4OCH3)] ligated first atomically precise silver NCs [Ag21{S2P(OR)(p-C6H4OCH3)}12]PF6 {where, R = nPr (1), Et (2)} were established by single-crystal X-ray diffraction and characterized by electrospray ionization mass spectrometry, NMR (31P, 1H, 2H), X-ray photoelectron spectroscopy, UV-visible, energy-dispersive X-ray spectroscopy, Fourier transforms infrared, thermogravimetric analysis, etc. NCs 1 and 2 consist of eight silver atoms in a cubic framework and enclose an Ag@Ag12-centered icosahedron to constitute an Ag21 core of Th symmetry, which is concentrically inscribed within the S24 snub-cube, P12 cuboctahedron, and the O12 truncated tetrahedron formed by 12 dithiophosphonate ligands. These NCs facilitate to be an eight-electron superatom (1S21P6), in which eight capping Ag atoms exhibit structural isomerism with documented isoelectronic [Ag21{S2P(OiPr)2}12]PF6, 3. In contrast to 3, the stapling of dithiophosphonates in 1 and 2 triggered bluish emission within the 400 to 500 nm region at room temperature. The density functional theory study rationalized isomerization and optical properties of 1, 2, and 3. Both (1, and 2) clusters catalyzed a decarboxylative acylarylation reaction for rapid oxindole synthesis in 99% yield under ambient conditions and proposed a multistep reaction pathway. Ultimately, this study links nanostructures to their physical and catalytic properties.

Heptanuclear Silver Hydride Clusters as Catalytic Precursors for the Reduction of 4-Nitrophenol

We report on the design, synthesis, and characterization of the first silver hydride clusters solely protected and stabilized by dithiophosphonate ligands and their application for the in situ generation of silver nanoparticles towards the catalytic reduction of 4-nitrophenol in an aqueous system. The synthesis of the silver monohydride cluster involves the incorporation of an interstitial hydride using sodium borohydride. Poly-nuclear magnetic resonance and mass spectrometry were used to establish the structural properties. The structural properties were then confirmed with a single-crystal X-ray diffraction analysis, which showed a distorted tetracapped tetrahedron core with one hydride ion encapsulated within the core of the silver framework. Additionally, the synthesized heptanuclear silver hydride was utilized as a precursor for the in situ generation of silver nanoparticles, which simultaneously catalyzed the reduction of 4-nitrophenol. The mechanism of the catalytic activity was investigated by first synthesizing AgNPs, which was subsequently used as a catalyst. The kinetic study showed that the pseudo-first constant obtained using the cluster (2.43 × 10−2 s−1) was higher than that obtained using the synthesized AgNPs (2.43 × 10−2 s−1). This indicated that the silver monohydride cluster was more active owing to the release of the encapsulated hydride ion and greater reaction surface prior to aggregation.

Dithiophosphonate Anchored Heterometallic (Ag(I)/Fe(II)) Molecular Catalysts for Electrochemical Hydrogen Evolution Reaction

The dichalcogenide ligated molecules in catalysis to produce molecular hydrogen through electroreduction of water are rarely explored. Here, a series of heterometallic [Ag₄(S₂PFc(OR)₄] [where Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅), R = Me, 1; Et, 2; ⁿPr, 3; ^isoAmyl, 4] clusters were synthesized and characterized by IR, absorption spectroscopy, NMR (¹H, ³¹P), and electrospray ionization mass spectrometry. The molecular structures of 1, 2, and 3 clusters were established by single-crystal X-ray crystallographic analysis. The structural elucidation shows that each triangular face of a tetrahedral silver(I) core is capped by a ferrocenyl dithiophosphonate ligand in a trimetallic triconnective (η³; μ₂, μ₁) pattern. A comparative electrocatalytic hydrogen evolution reaction of 1-5 (R = ⁱPr, 5) was studied in order to demonstrate the potential of these clusters in water splitting activity. The experimental results reveal that catalytic performance decreases with increases in the length of the carbon chain and branching within the alkoxy (-OR) group of these clusters. Catalytic durability was found effective even after 8 h of a chronoamperometric stability test along with 1500 cycles of linear sweep voltammetry performance, and only 15 mV overpotential was increased at 5 mA/cm² current density for cluster 1. A catalytic mechanism was proposed by applying density functional theory (DFT) on clusters 1 and 2 as a representative. Here, a μ₁ coordinated S-site between Ag₄ core and ligand was found a reaction center. The experimental results are also in good accordance with the DFT analysis.

Silver(I) and Gold(I) Monothiocarbonate Complexes: Synthesis, Structure, Luminescence

The monothiocarbonate ligand, [S(O)COR]−, is unusual and rare regarding its use in the formation of coordination compounds. Here, we report the synthesis and structures of the silver(I) and gold(I) monothiocarbonate complexes, [{Ag4(SC(O)OiPr)2(2,2′-bpy)4}(PF6)2]n (1) and [Au2{S(O)COiPr}2(dppe)]n (2), respectively. Both complexes are coordination polymers, with 1 being cationic and 2 neutral. The uniqueness of the ligand is that it is monoanionic and contains both a ‘hard’ O-donor ligand and a ‘soft’ S-donor ligand in a O-C-S manifold with, in principle, electron delocalization across the three atoms. However, for both complexes 1 and 2, it was found that the binding occurred exclusively through the S-donor atom, while the C=O portion remained dangling and was not involved in bonding. This bonding mode departs significantly from the symmetrical S-C-S type ligand such as dithiocarbamates. The structures were analysed and confirmed by NMR and X-ray crystallography.

Inorganic Pb(II)-P and Pb(II)-S Complexes as Photosensitizers from Primary and Secondary Amines in Dyes-Sensitized Solar Cells

Pb(II) complexes of bis(N-1,4-phenyl-N-(4-morpholinedithiocarbamato)) as Pb(II)-S and bis(N-diisopropyl-N-octyldithiocarbamato) as Pb(II)-P were prepared and characterized by optical, structural, morphological, and electrochemical techniques. The scanning electron microscopy analysis of Pb(II)-P and Pb(II)-S complexes consists of cubic crystals. X-ray diffraction and high-resolution transmission electron microscopy spectral studies revealed that the diameter increases in length for alkyl chain groups. This study demonstrates that the cubic shape of Pb(II) complexes can be synthesized from aromatic and aliphatic dithiocarbamate ligands. Photoluminescence analysis of both complexes fell within the blue shift region. The CV curve for Pb(II)-S revealed redox curves and the box-like shape as an indicative of a capacitive behavior, signifying limited catalytic redox activity. The J-V results for both sensitizers displayed satisfactory conversion efficiency (% η) between 3.77 and 3.96%.

Synergistically enhanced performance of transition-metal doped Ni2P for supercapacitance and overall water splitting

Cost-effective and readily available catalysts applicable for electrochemical conversion technologies are highly desired. Herein, we report the synthesis of dithiophosphonate complexes of the type [Ni{S₂P(OH)(4-CH₃OC₆H₄)}₂] (1), [Co{S₂P(OC₄H₉)(4-CH₃OC₆H₄)}₃] (2) and [Fe{S₂P(OH)(4-CH₃OC₆H₄)}₃] (3) and employed them to prepare Ni₂P, Co-Ni₂P and Fe-Ni₂P nanoparticles. Ni₂P was formed by a facile hot injection method by decomposing complex 1 in tri-octylphosphine oxide/tri-n-octylphosphine at 300 °C. The prepared Ni₂P was doped with Co and Fe employing complexes 2 and 3, respectively, under similar experimental conditions. Doping Ni₂P with Co and Fe demonstrated synergistic improvement of Ni₂P performance as an electrocatalyst in supercapcitance, hydrogen evololution and oxygen evolution reactions in alkaline medium. Cobalt doping improved the Ni₂P charge storage capacity with a supercapacitance of 864 F g^-1 at 1 A g^-1 current density. Fe doped Ni₂P recorded the lowest overpotential of 259 mV to achieve a current density of 10 mA cm^-2 and a Tafel slope of 80 mV dec^-1 for OER, better than the undoped Ni₂P and the benchmark IrO₂. Likewise, Fe-doped Ni₂P electrode required the lowest overpotential of 68 mV with a Tafel slope of 110 mV dec^-1 to attain the same current density for HER. All catalysts showed excellent stability in supercapacitance and overall water splitting reactions, indicating their practical use in energy conversion technologies.

Triphenylphosphine-Assisted Transformation of NiS to Ni2P through a Solvent-Less Pyrolysis Route: Synthesis and Electrocatalytic Performance

Straightforward synthetic routes to the preparation of transition metal phosphides or their chalcogenide analogues are highly desired due to their widespread applications, including catalysis. We report a facile and simple route for the preparation of a pure phase nickel phosphide (Ni₂P) and phase transformations in the nickel sulfide (NiS) system through a solvent-less synthetic protocol. Decomposition of different sulfur-based complexes (dithiocarbamate, xanthate, and dithiophosphonate) of nickel(II) was investigated in the presence and absence of triphenylphosphine (TPP). The optimization of reaction parameters (nature of precursor, ratio of TPP, temperature, and time) indicated that phosphorus- and sulfur-containing inorganic dithiophosphonate complexes and TPP (1:1 mole ratio) produced pure nickel phosphide, whereas different phases of nickel sulfide were obtained from dithiocarbamate and xanthate precursors in the presence or absence of TPP. A plausible explanation of the sulfide or phosphide phase formation is suggested, and the performance of Ni₂P was investigated as an electrocatalyst for supercapacitance and overall water-splitting reactions. The performance of Ni₂P with the surface free of any capping agents is not well explored, as common synthetic methods are solution-based routes; therefore, the electrocatalytic performance was also compared with metal phosphides, prepared by other routes. The highest specific capacitance of 367 F/g was observed at 1 A/g, and the maximum energy and power density of Ni₂P were calculated to be 17.9 Wh/kg and 6951 W/kg, respectively. The prepared nickel phosphide required overpotentials of 174 and 316 mV along with Tafel slopes of 115 and 95 mV/dec to achieve a current density of 10 mA/cm² for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively.

Morpholine- and Thiomorpholine-Based Amidodithiophosphonato Nickel Complexes: Synthesis, Characterization, P-N Cleavage, Antibacterial Activity and Silica Nano-Dispersion

The reactivity of thiomorpholinium P-(4-methoxyphenyl)-N-thiomorpholin-amidodithiophosphonate (S-MorH⁺₂)(S-Mor-adtp^-) and morpholinium P-(4-methoxyphenyl)-N-morpholin-amidodithiophosphonate (O-MorH⁺₂)(O-Mor-adtp^-) towards nickel (II) dichloride hexahydrated is presented and the hydrolysis of the relevant metal complexes investigated. The hydrolytic products (S-MorH⁺₂)₂ [Ni(dtp)₂]²- and (O-MorH⁺₂)₂[Ni(dtp)₂]²- were characterized by means of FT-IR, ¹H, and ³¹P NMR and XRD and the experimented P-N cleavage investigated and elucidated by means of DFT calculations. The antimicrobial activity of the neutral nickel complex [Ni(S-Mor-adtp)₂] was tested against a set of Gram-positive and Gram-negative bacteria alongside with its nanodispersion in a silica matrix. The complex [Ni(S-Mor-adtp)₂] did not show antibacterial activity, whilst the nano-dispersed sample [Ni(S-Mor-adtp)₂]_SiO₂ demonstrated inhibition to growth of Staphylococcus aureus. The nanocomposites were fully characterized by means of XRPD, TGA, SEM and dinitrogen sorption techniques.

Isolation and Characterization of the Free Phenylphosphinidene Chalcogenides C6 H5 P=O and C6 H5 P=S, the Phosphorous Analogues of Nitrosobenzene and Thionitrosobenzene

The structures and reactivities of organic phosphinidene chalcogenides have been mainly inferred from trapping or complexation experiments. Phosphinidene chalcogenide derivatives appear to be an elusive family of molecules that have been suggested as reactive intermediates in multiple organophosphorus reactions. The quest to isolate "free" phosphinidene chalcogenides remains a challenge in the field. Here, we present the synthesis, IR, and UV/Vis spectroscopic identification of hitherto elusive phenylphosphinidene oxide and phenylphosphinidene sulfide from the corresponding phosphonic diazide precursors. We isolated these higher congeners of nitroso- and thionitrosobenzene in argon matrices at 10 K. The spectral assignments are supported by B3LYP/6-311++G(3df,3pd) and MP2/cc-pVTZ computations.

Antibacterial Activity of Amidodithiophosphonato Nickel(II) Complexes: An Experimental and Theoretical Approach

The reactions of 2,4-bis(4-methoxyphenyl)-1,3-dithio-2,4-diphosphetane-2,4-disulfide (Lawesson's Reagent, LR) with benzylamine (BzNH2) and 4-phenylbutylamine (PhBuNH2) yield benzylammonium P-(4-methoxyphenyl)-N-benzyl-amidodithiophosphonate (BzNH3)(BzNH-adtp) and 4-phenylbutylammonium P-(4-methoxyphenyl)-N-(4-phenylbutyl)-amidodithiophosphonate (PhBuNH3)(PhBuNH-adtp). The relevant nickel complexes [Ni(BzNH-adtp)2] and [Ni(PhBuNH-adtp)2] and the corresponding hydrolysed derivatives (BzNH3)2[Ni(dtp)2] and (PhBuNH3)2[Ni(dtp)2] were prepared and fully characterized. The antimicrobial activity of the aforementioned amidodithiophosphonates against a set of Gram-positive and Gram-negative pathogen bacteria was evaluated, and [Ni(BzNH-adtp)2] and [Ni(PhBuNH-adtp)2] showed antiproliferative activity towards Staphylococcus aureus and Staphylococcus haemolyticus strains. density functional theory (DFT) calculations were performed to shed some light on the activity of reported compounds related to their tendency towards P-N bond cleavage.

Synthesis of the first chiral polynuclear copper(i) complex based on (R)-1-(1-phenyl)ethyl-3-(O,O-diethylthiophosphoryl)thiourea and its characterization in the solid state and solution

The reaction of chiral N-thiophosphorylated thiourea with Cu(ii) acetate is accompanied by copper reduction and leads to the formation of a polynuclear complex with the core composed of six Cu(i) ions alternating with sulfur atoms.

New main-group ferrocenyldithiocarbamates and conversion to ferrocene oxazolidine-2-thione and -2-one

Three new main-group ferrocenyl dithiocarbamates and a pure cyclised product, 3-ferrocenylmethyl-oxazolidine-2-thione, were isolated using copper powder.

Medium-sized cyclic bis(anisylphosphonothioyl)disulfanes and their corresponding cyclic sulfane-structures and most characteristic reactions

A family of cyclic medium-sized disulfanes and related sulfanes was synthesized and characterized, followed by desulfurization and disulfane ammonolysis.

Unravelling Lawesson's reagent: the structure of monomeric (4-methoxyphenyl)phosphine disulfide

We describe the isolation as well as IR and UV/Vis spectroscopic characterization of (4-methoxyphenyl)phosphine disulfide in argon matrices at 10 K. The title compound proved to be highly photolabile; irradiation with UV light (λ = 334 nm) led to rearrangement to the equally unreported 3-(4-methoxyphenyl)-1,2,3-dithiaphosphirane. Photoreversion can be achieved upon irradiation at λ = 465 nm.

1,2-Bis(diphenylphosphino)ethane nickel(ii) O,O′-dialkyldithiophosphates as potential precursors for nickel sulfides

Three new dppe nickel(ii) dithiophosphates with different counteranions synthesized and decomposed to obtain Ni–S systems with same phase independent of the nature of counteranions and alkyl fragments.

Exploring the crystallization landscape of cadmium bis(N-hydroxyethyl, N-isopropyldithiocarbamate), Cd[S2CN(iPr)CH2CH2OH]2

Crystallization of Cd[S2CN(iPr)CH2CH2OH]2 from ethanol yields the coordination polymer [{Cd[S2CN(iPr)CH2CH2OH]2}·EtOH]∞ (1) within 3 h. When the solution is allowed to stand for another hour, the needles begin to dissolve and prisms emerge of the supramolecular isomer (SI), binuclear {Cd[S2CN(iPr)CH2CH2OH]2}2·2EtOH (2). These have been fully characterized spectroscopically and by X-ray crystallography. Polymeric 1 has 2-fold symmetry and features dithiocarbamate ligands coordinating two octahedral Cd atoms in a μ 2 κ 2-tridentate mode. Binuclear 2 is centrosymmetric with two ligands being μ 2 κ 2-tridentate as for 1 but the other two being κ 2-chelating leading to square pyramidal geometries. The conversion of the kinetic crystallization product, 1, to thermodynamic 2 is irreversible but transformations mediated by recrystallization (ethanol and acetonitrile) to related literature SI species, namely coordination polymer [{Cd[S2CN(iPr)CH2CH2OH]2}3·MeCN]∞ and binuclear {Cd[S2CN(iPr)CH2CH2 OH]2}2·2H2O·2MeCN, are demonstrated, some of which are reversible. Three other crystallization outcomes are described whereby crystal structures were obtained for the 1:2 co-crystal {Cd[S2CN(iPr)CH2CH2OH]2}2:2[3-(propan-2-yl)-1,3-oxazolidine-2-thione] (3), the salt co-crystal [iPrNH2(CH2CH2OH)]4[SO4]2{Cd[S2CN(iPr)CH2CH2OH]2}2 (4) and the salt [iPrNH2(CH2CH2OH)]{Cd[S2CN(iPr)CH2CH2OH]3} (5). These arise as a result of decomposition/oxidation of the dithiocarbamate ligands. In each of 3 and 4 the binuclear {Cd[S2CN(iPr)CH2CH2OH]2}2 SI, as in 2, is observed strongly suggesting a thermodynamic preference for this form.