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The nitride ligand in the iron(IV) complex PhB(

Herein, we report the reactions of an Fe(II) imido complex [Ph

Open-shell organic molecules, including S = ½ radicals, may provide enhanced properties for several emerging technologies, however, relatively few synthesized to date possess robust thermal stability and processability. We report synthesis of S = ½ biphenylene-fused tetrazolinyl radicals 1 and 2. Both radicals possess near-perfect planar structures based on their X-ray structures and DFT computations. Radical 1 possesses an outstanding thermal stability as indicated by the onset of decomposition at 269 °C, based on thermogravimetric analysis (TGA) data. Both radicals possess very low oxidation potentials < 0 V (vs. SCE) and their electrochemical energy gaps, Ecell 0.9 eV, are rather low. Magnetic properties of polycrystalline 1 are characterized by SQUID magnetometry revealing a one-dimensional S = ½ antiferromagnetic Heisenberg chain with exchange coupling constant J’/k –22.0 K. Radical 1 in toluene glass possesses a long electron spin coherence time, Tm ≈ 7 μs in the 40 – 80 K temperature range, a property advantageous for potential applications as a molecular spin qubit. Radical 1 is evaporated under ultrahigh vacuum (UHV) forming assemblies of intact radicals on a silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy (XPS). Scanning electron microscope (SEM) images indicate that the radical molecules form nanoneedles on the substrate. The nanoneedles are stable for at least 64 hours under air as monitored by using X-ray photoelectron spectroscopy. EPR studies of the thicker assemblies, prepared by UHV evaporation, indicate radical decay according to first-order kinetics with a long half-life of 50 +/-4 days at ambient conditions.

Carboxylic acid substitution in 1,10-phenanthroline-5,6-dione ligands bind to surface hydroxy groups and result in higher ligand loading for metal–ligand single-atom Pt catalysts on CeO2, thereby allowing excellent hydrosilylation catalysis.

N-type HfS3in vacuo (left) versus p-type HfS3 in air (right); O2 chemisorption changes the n-type EF to p-type EF.

Two-coordinate silylamido complexes of nickel and copper rapidly react with CO

There has been an increasing interest in chemistry involving nitrogen oxyanions, largely due to the environmental hazards associated with increased concentrations of these anions leading to eutrophication and aquatic "dead zones". Herein, we report the synthesis and characterization of a suite of MNOx complexes (M = Co, Zn: x = 2, 3). Reductive deoxygenation of cobalt bis(nitrite) complexes with bis(boryl)pyrazine is faster for cobalt than previously reported nickel, and pendant O-bound nitrito ligand is still readily deoxygenated, despite potential implication of an isonitrosyl primary product. Deoxygenation of zinc oxyanion complexes is also facile, despite zinc being unable to stabilize a nitrosyl ligand, with liberation of nitric oxide and nitrous oxide, indicating N-N bond formation. X-ray photoelectron spectroscopy is effective for discriminating the types of nitrogen in these molecules. ESI mass spectrometry of a suite of M(NOx)y (x = 2, 3 and y = 1, 2) shows that the primary form of ionization is loss of an oxyanion ligand, which can be alleviated via the addition of tetrabutylammonium (TBA) as a nonintuitive cation pair for the neutral oxyanion complexes. We have shown these complexes to be subject to deoxygenation, and there is evidence for nitrogen oxyanion reduction in several cases in the ESI plume. The attractive force between cation and neutral is explored experimentally and computationally and attributed to hydrogen bonding of the nitrogen oxyanion ligands with ammonium α-CH2 protons. One example of ESI-induced reductive dimerization is mimicked by bulk solution synthesis, and that product is characterized by X-ray diffraction to contain two Co(NO)2+ groups linked by a highly conjugated diazapolyene.

Synthesis of bis-spiro-oxetane and bis-spiro-tetrahydrofuran pyrroline nitroxide radicals relies on the Mitsunobu reaction-mediated double cyclizations of N-Boc protected pyrroline tetraols. Structures of the nitroxide radicals are supported by X-ray crystallography. In a trehalose/sucrose matrix at room temperature, the bis-spiro-oxetane nitroxide radical possesses electron spin coherence time, Tm ≈ 0.7 μs. The observed enhanced Tm is most likely associated with strong hydrogen bonding of oxetane moieties to the trehalose/sucrose matrix.

Aspects of the proposed pathway combining chain-end and enantiomorphic site control for the stereospecific polymerization of lactide (LA) were investigated through studies of aluminum complexes supported by enantiopure and racemic bipyrrolidine-based salan ligands, Lig

We report high-spin aminyl triradicals with near-planar triphenylene backbones. Near-planarity of the fused aminyl radicals and the 2,6,10-triphenylene ferromagnetic coupling unit (FCU), magnetically equivalent to three fused 3,4'-biphenyl FCUs, assures an effective 2p

The reaction chemistry of the bis-tetrazinyl pyridine ligand (btzp) towards nitrogen oxyanions coordinated to zinc is studied in order to explore the reduction of the NOx- substrates with a redox-active ligand in the absence of redox activity at the metal. Following syntheses and characterization of (btzp)ZnX2 for X=Cl, NO3 and NO2 , featuring O-Zn linkage of both nitrogen oxyanions, it is shown that a silylating agent selectively delivers silyl substituents to tetrazine nitrogens, without reductive deoxygenation of NOx-1 . A new synthesis of the highly hydrogenated H4 btzp, containing two dihydrotetrazine reductants is described as is the synthesis and characterization of (H4 btzp)ZnX2 for X=Cl and NO3 , both of which show considerable hydrogen bonding potential of the dihydrotetrazine ring NH groups. The (H4 btzp)ZnCl2 complex does not bind zinc in the pincer pocket, but instead H4 btzp becomes a bridge between neighboring atoms through tetrazine nitrogen atoms, forming a polymeric chain. The reaction of AgNO2 with (H4 btzp)ZnCl2 is shown to proceed with fast nitrite deoxygenation, yielding water and free NO. Half of the H4 btzp reducing equivalents form Ag0 and thus the chloride ligand remains coordinated to the zinc metal center to yield (btzp)ZnCl2 . To compare with AgNO2 , experiments of (H4 btzp)ZnCl2 with NaNO2 result in salt metathesis between chloride and nitrite, highlighting the importance of a redox-active cation in the reduction of nitrite to NO.

X-ray photoemission spectroscopy (XPS) has been used to examine the interaction between Au and HfS

Reduction of the three-coordinate iron(III) imido [Ph2B(tBuIm)2Fe═NDipp] (1) affords [Ph2B(tBuIm)2Fe═NDipp][K(18-C-6)THF2] (2), a rare example of a high-spin (S = 2) iron(II) imido complex. Unusually for a late metal imido complex, the imido ligand in 2 has nucleophilic character, as demonstrated by the reaction with DippNH2, which establishes an equilibrium with the bis(anilido) complex [Ph2B(tBuIm)2Fe(NHDipp)2][K(18-C-6)THF2] (3). In an unusual transformation, formal insertion of iPrN═C═NiPr into the Fe═N(imido) bond yields the guanidinate [Ph2B(tBuIm)2Fe(iPrN)2CNDipp][K(18-C-6)THF2] (4). Reaction of 4 with excess DippNH2 provides 3, along with the guanidine (iPrNH)2C═NDipp. As suggested by these stoichiometric reactions, 2 is an efficient catalyst for the guanylation of carbodiimides, converting a wide range of aniline substrates under mild conditions.

The syntheses of (DIM)Ni(NO3)2 and (DIM)Ni(NO2)2, where DIM is a 1,4-diazadiene bidentate donor, are reported to enable testing of bis boryl reduced N-heterocycles for their ability to carry out stepwise deoxygenation of coordinated nitrate and nitrite, forming O(Bpin)2. Single deoxygenation of (DIM)Ni(NO2)2 yields the tetrahedral complex (DIM)Ni(NO)(ONO), with a linear nitrosyl and κ1-ONO. Further deoxygenation of (DIM)Ni(NO)(ONO) results in the formation of dimeric [(DIM)Ni(NO)]2, where the dimer is linked through a Ni–Ni bond. The lost reduced nitrogen byproduct is shown to be N2O, indicating N–N bond formation in the course of the reaction. Isotopic labelling studies establish that the N–N bond of N2O is formed in a bimetallic Ni2 intermediate and that the two nitrogen atoms of (DIM)Ni(NO)(ONO) become symmetry equivalent prior to N–N bond formation. The [(DIM)Ni(NO)]2 dimer is susceptible to oxidation by AgX (X = NO3−, NO2−, and OTf−) as well as nitric oxide, the latter of which undergoes nitric oxide disproportionation to yield N2O and (DIM)Ni(NO)(ONO). We show that the first step in the deoxygenation of (DIM)Ni(NO)(ONO) to liberate N2O is outer sphere electron transfer, providing insight into the organic reductants employed for deoxygenation. Lastly, we show that at elevated temperatures, deoxygenation is accompanied by loss of DIM to form either pyrazine or bipyridine bridged polymers, with retention of a BpinO− bridging ligand., Deoxygenation of nitrogen oxyanions coordinated to nickel using reduced borylated heterocycles leads to N–N bond formation and N2O liberation. The nickel dimer product facilitates NO disproportionation, leading to a synthetic cycle.

The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R-BF

Triplet ground-state organic molecules are of interest with respect to several emerging technologies but usually show limited stability, especially as thin films. We report an organic diradical, consisting of two Blatter radicals, that possesses a triplet ground state with a singlet-triplet energy gap, Δ

Double deprotonation of the salt [Ph2B(PMe3)2][OTf] (1) provides access to a bis(ylide)diphenylborate ligand that is readily transferred in situ to iron(II). Depending on the reaction stoichiometry, both the "ate" complex [Ph2B(Me2PCH2)2Fe(μ-Cl)2Li(THF)2] (2) and the homoleptic complex [Ph2B(Me2PCH2)2]2Fe(3) can be prepared from FeCl2(THF)1.5. Further reaction of 3 with FeCl2(THF)1.5 produces the chloride-bridged dimer [Ph2B(Me2PCH2)2Fe(μ-Cl)2Fe(CH2PMe2)2BPh2](4). Attempts to reduce or alkylate 4 provide 3 as the only isolable product, likely a consequence of the low steric hindrance of the bis(ylide)diphenylborate ligand. On the other hand, reaction of 4 with the strong field ligand CNtBu provides the six-coordinate, diamagnetic complex [Ph2B(Me2PCH2)2Fe(CNtBu)4][Cl](5). Electronic structure calculations for the bis(ylide)diphenylborate ligand and homoleptic complex 3 suggest that the C(ylide) atoms are strong σ-donors with little π-bonding character. These initial results suggest the potential for this bis(ylide)diphenylborate ligand in coordination chemistry.

The N2 analogue phosphorus nitride (PN) was the first phosphorus-containing compound to be detected in the interstellar medium; however, this thermodynamically unstable compound has a fleeting existence on Earth. Here, we show that reductive coupling of iron(IV) nitride and molybdenum(VI) phosphide complexes assembles PN as a bridging ligand in a structurally characterized bimetallic complex. Reaction with C≡NtBu releases the mononuclear complex [(N3N)Mo—PN]−, N3N = [(Me3SiNCH2CH2)3N]3–), which undergoes light-induced linkage isomerization to provide [(N3N)Mo—NP]−, as revealed by photocrystallography. While structural and spectroscopic characterization, supported by electronic structure calculations, reveals the PN multiple bond character, coordination to molybdenum induces a nucleophilic character at the terminal atom of the PN/NP ligands. Indeed, the linkage isomers can be trapped in solution by reaction with a Rh(I) electrophile., The highly reactive interstellar gas, phosphorus nitride, is assembled and stabilized as a reactive ligand in transition metal complexes.

We demonstrate a host-guest molecular recognition approach to advance double electron-electron resonance (DEER) distance measurements of spin-labeled proteins. We synthesized an iodoacetamide (IA) derivative of 2,6-diazaadamantane nitroxide (DZD) spin label that could be doubly incorporated into T4 Lysozyme (T4L) by site-directed spin labeling (SDSL) with efficiency up to 50% per cysteine. The rigidity of the fused ring structure and absence of mobile methyl groups increase the spin echo dephasing time (T(m)) at temperatures above 80 K. This enables DEER measurements of distances >4 nm in DZD labeled-T4L in glycerol/water at temperatures up to 150 K, with increased sensitivity compared to common spin label such as MTSL. Addition of β-cyclodextrin (β-CD) reduces the rotational correlation time of the label, slightly increases T(m), and most importantly, narrows (and slightly lengthens) the inter-spin distance distributions. The distance distributions are in good agreement with simulated distance distributions obtained by rotamer libraries. These results provide a foundation for developing supramolecular recognition to facilitate long-distance DEER measurements at near physiological temperatures.

Sequence-controlled supramolecular polymers offer new design paradigms for generating stimuli-responsive macromolecules with enhanced functionalities. The dynamic character of supramolecular links present challenges to sequence definition in extended supramolecular macromolecules, and design principles remain nascent. Here, we demonstrate the first example of using stoichiometry-control to specify the monomer sequence in a linear supramolecular polymer by synthesizing both a homopolymer and an alternating copolymer from the same glycol-substituted cyanostar macrocycle and phenylene-linked diphosphate monomers. A 2:1 stoichiometry between macrocycle and diphosphate produces a supramolecular homopolymer of general formula (A)n comprised of repeating units of cyanostar-stabilized phosphate-phosphate dimers. Using a 1:1 stoichiometry, an alternating (AB)n structure is produced with half the phosphate dimers now stabilized by the additional counter cations that emerge hierarchically after forming the stronger cyanostar-stabilized phosphate dimers. These new polymer materials and binding motifs are sufficient to bear normal and shear stress to promote significant and tunable adhesive properties. The homopolymer (A)n, consisting of cyanostar-stabilized anti-electrostatic linkages, shows adhesion strength comparable to commercial superglue formulations based on polycyanoacrylate but is thermally reversible. Unexpectedly, and despite including traditional ionic linkages, the alternating copolymer (AB)n shows weaker adhesion strength more similar to commercial white glue based on poly(vinyl acetate). Thus, the adhesion properties can be tuned over a wide range by simply controlling the stoichiometric ratio of monomers. This study offers new insight into supramolecular polymers composed of custom-designed anion and receptor monomers and demonstrates the utility of emerging functional materials based on anion-anion linkages.

Triplet ground-state organic molecules are of interest with respect to several emerging technologies but usually show limited stability, especially as thin films. We report an organic diradical, consisting of two Blatter radicals, that possesses a triplet ground state with a singlet-triplet energy gap, ?EST? 0.4-0.5 kcal mol-1(2J/k ? 220-275 K). The diradical possesses robust thermal stability, with an onset of decomposition above 264 °C (TGA). In toluene/chloroform, glassy matrix, and fluid solution, an equilibrium between two conformations with ?EST? 0.4 kcal mol-1and ?EST? -0.7 kcal mol-1is observed, favoring the triplet ground state over the singlet ground-state conformation in the 110-330 K temperature range. The diradical with the triplet ground-state conformation is found exclusively in crystals and in a polystyrene matrix. The crystalline neutral diradical is a good electrical conductor with conductivity comparable to the thoroughly optimized bis(thiazolyl)-related monoradicals. This is surprising because the triplet ground state implies that the underlying ?-system is cross-conjugated and thus is not compatible with either good conductance or electron delocalization. The diradical is evaporated under ultra-high vacuum to form thin films, which are stable in air for at least 18 h, as demonstrated by X-ray photoelectron and electron paramagnetic resonance (EPR) spectroscopies

The two-electron reduction of the Ti(IV) guanidinate (Ketguan)(ImDippN)Ti(OTf)2 (2OTf) (Ketguan = [(tBu2C═N)C(NDipp)2]−; ImDippN– = 1,3-bis(Dipp)imidazolin-2-iminato; Dipp = 2,6-diisopropylphenyl) with an excess of KC8 generates the masked complex (Ketguan)(η6-ImDippN)Ti (1). Conversely, reduction of the chloride analogue (Ketguan)(ImDippN)TiCl2 (2Cl) with an excess of Na/Hg amalgam produces the Ti(III) compound (Ketguan)(ImDippN)TiCl (3), while treatment of 2Cl with 3.0 equiv of KC8 affords a complicated mixture from which (ImDippN)(DippN═)[η2-(tBu2C)NC(NDipp)](THF)Ti (4) is isolated as the product of reductive ligand cleavage. These results clearly indicate that the success of early metal reduction chemistry is highly sensitive to the halide coligands and reaction conditions. Complex 1, despite possessing a Ti(IV) canonical form, behaves as a Ti(II) synthon and appreciable reducing agent. For instance, 1 effects the one-electron reduction of benzophenone and pyridine to give the Ti(III) products (Ketgua...

Rigid pyridylphenylene dendrons were shown to successfully function as capping molecules for stabilization of both magnetite and Pd nanoparticles (NPs) to form hydrophobic, magnetically recoverable catalysts. However, syntheses in colloidal solutions require large amounts of dendrons and are difficult to scale up. Here, we developed a strategy for the nanocomposite formation by immobilization of the pyridylphenylene dendrons (D) on magnetic silica (Fe3O4-SiO2, MS) surface via the formation of ether or amide bonds, depending on the structure of flexible linkers on the MS surface and dendron focal groups. Both approaches allow attachment of small amounts of the dendrons with high surface coverage and impart amphiphilicity to the final composite. After the binding to the MS surface, the dendron pyridine moieties readily complex with Pd acetate, leading to a “cocktail” of Pd2+ and Pd0 species (the latter forming Pd NPs) due to partial reduction by composite functional groups. The MS-D-Pd nanocomposites were tested in the model Suzuki-Miyaura cross-coupling reaction of 4-Br-anisole and phenylboronic acid to evaluate their performance in hydrophilic conditions. MS-D-Pd demonstrated excellent performance, even at a very small amount of the catalyst, which is assigned to exceptional stabilization by dendritic ligands, allowing prevention of the metal leaching and preservation of catalytic properties upon magnetic separation. The immobilization of rigid hydrophobic dendrons on the hydrophilic magnetic support may allow one to extend the scope of catalytic reactions due to catalyst amphiphilicity.

International audience; The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(h5-C5R5)2]+ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(h5-C5Me5)2]BArF are revealed. Multireference quantum mechanical calculationsshow a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible forthe SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(h5-C5Bn5)2]BF4 and [Fe(h5-C5Bn5)2]PF6, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems.

Structural and spectroscopic characterization of the dimeric iron hydride complex [Ph2B(tBuIm)2FeH]2 reveals an unusual structure in which a tetrahedral iron(II) site (S = 2) is connected to a squa...

High spin (S = 1) organic diradicals may offer enhanced properties with respect to several emerging technologies, but typically exhibit low singlet triplet energy gaps and possess limited thermal stability. We report triplet ground state diradical 2 with a large singlet-triplet energy gap, ΔE(ST) ≥ 1.7 kcal mol(−1), leading to nearly exclusive population of triplet ground state at room temperature, and good thermal stability with onset of decomposition at ~160 °C under inert atmosphere. Magnetic properties of 2 and the previously prepared diradical 1 are characterized by SQUID magnetometry of polycrystalline powders, in polystyrene glass, and in other matrices. Polycrystalline diradical 2 forms a novel one-dimensional (1D) spin-1 (S = 1) chain of organic radicals with intrachain antiferromagnetic coupling of J′/k = −14 K, which is associated with the N···N and N···O intermolecular contacts. The intrachain antiferromagnetic coupling in 2 is by far strongest among all studied 1D S = 1 chains of organic radicals, which also makes 1D S = 1 chains of 2 most isotropic, and therefore an excellent system for studies of low-dimensional magnetism. In polystyrene glass and in frozen benzene or dibutyl phthalate solution, both 1 and 2 are monomeric. Diradical 2 is thermally robust and is evaporated under ultra-high vacuum to form thin films of intact diradicals on silicon substrate, as demonstrated by X-ray photoelectron spectroscopy. Based on C-K NEXAFS spectra and AFM images of the ~1.5-nm thick films, the diradical molecules form islands on the substrate with molecules stacked approximately along the crystallographic a-axis. The films are stable under ultra-high vacuum for at least 60 h but show signs of decomposition when exposed to ambient conditions for 7 h.

The consequences of installing two versions of a potentially redox active pincer ligand on Cr(III) and Cr(II) are described, and reveal influence of the Jahn-Teller effect. The ligand involves two pyrazole rings attached by pyrazole carbons to the ortho positions of pyridine, thus creating two 1,4-diazabutadiene moieties. In one version, each pyrazole carries an NH proton (H2L), while a comparison version (LMe) involves methyl in place of the two weakly acidic protons, to identify the impact of hydrogen bonding. Complexes synthesized include (H2L)CrX3, where X Cl, triflate and nitrate, (LMe)CrCl3 and (LMe)Cr(OTf)3, together with the divalent metal complexes (H2L)CrCl2, (LMe)CrCl2 and (LMe)Cr(OTf)2. Cyclic voltammetry establishes the relationship between the tri- and divalent triflate complexes of LMe, and DFT calculations indicate further reduction of the latter occurs at the LMe ligand. Nitrate is shown to be a stronger ligand than triflate to Cr(III) here. NaBArF24 in THF removes only one chloride from (H2L)CrCl2, to give square pyramidal [(H2L)CrCl(THF)]+.

The direct, catalytic substitution of unactivated alcohols remains an undeveloped area of organic synthesis. Moreover, catalytic activation of this difficult electrophile with predictable stereo-outcomes presents an even more formidable challenge. Described herein is a simple iron-based catalyst system which provides the mild, direct conversion of secondary and tertiary alcohols to sulfonamides. Starting from enantioenriched alcohols, the intramolecular variant proceeds with stereoinversion to produce enantioenriched 2- and 2,2-subsituted pyrrolidines and indolines, without prior derivatization of the alcohol or solvolytic conditions.

Bis(carbene)borate ligand transfer to the nickel nitrosyl synthon Ni(NO)(PPh3)2Br provides the new nickel nitrosyl complex Ph2B(tBuIm)2Ni(NO)(PPh3). The solid state structure reveals a trigonal pyramidal nickel ion with a very long bond to the apical PPh3 ligand. The complex reversibly dissociates PPh3 in solution to afford three-coordinate Ph2B(tBuIm)2Ni(NO), with NMR data providing evidence for PPh3 binding at low temperatures. Ligand transfer to Ni(PMe3)2Cl2 provides the square planar complex, Ph2B(tBuIm)2Ni(PMe3)Cl, which shows no evidence for rearranging to the form a homoleptic complex with two bis(carbene)borate ligands. This complex is a suitable synthon for the [Ph2B(tBuIm)2Ni]+ fragment, as demonstrated by the synthesis of the π-allyl complex Ph2B(tBuIm)2Ni(η3-C7H7). The π-allyl complex reacts with O2 to provide benzaldehyde and an unstable complex that is tentatively identified as the nickel(II) hydroxide [Ph2B(tBuIm)2Ni(μ-OH)]2.

High spin (S = 3/2) organic triradicals may offer enhanced properties with respect to several emerging technologies, but those synthesized to date typically exhibit small doublet quartet energy gaps and/or possess limited thermal stability and processability. We report a quartet ground state triradical 3, synthesized by a Pd(0)-catalyzed radical-radical cross-coupling reaction, which possesses two doublet-quartet energy gaps, ΔE(DQ) ≈ 0.2 – 0.3 kcal mol(−1) and ΔE(DQ)2 ≈ 1.2 – 1.8 kcal mol(−1). The triradical has a 70+% population of the quartet ground state at room temperature, and good thermal stability with onset of decomposition at >160 °C under inert atmosphere. Magnetic properties of 3 are characterized by SQUID magnetometry in polystyrene glass and by quantitative EPR spectroscopy. Triradical 3 is evaporated under ultra-high vacuum to form thin films of intact triradicals on silicon substrate, as confirmed by high resolution X-ray photoelectron spectroscopy. AFM and SEM images of the ~1-nm thick films indicate that the triradical molecules form islands on the substrate. The films are stable under ultra-high vacuum for at least 17 h but show onset of decomposition after 4 h at ambient conditions. The drop-cast films are less prone to degradation in air and have longer lifetime.

Here, we report a one-pot solvothermal method for the development of magnetically recoverable catalysts with Ru or Ag nanoparticles (NPs) capped by chitosan (CS), a derivative of natural chitin. The formation of iron oxide NPs was carried out in situ in the presence of CS and iron acetylacetonate in boiling triethyleneglycol (TEG) due to CS solubilization in warm TEG. Coordination with Ru or Ag species and the NP formation take place in the same reaction solution, eliminating intermediate steps. In optimal conditions the method developed allows stabilization of 2.2 nm monodisperse Ru NPs (containing both Ru0 and Ru4+ species) that are evenly distributed through the catalyst, while for Ag NPs, this stabilizing medium is inferior, leading to exceptionally large Ag nanocrystals. Catalytic testing of CS-Ru magnetically recoverable catalysts in the reduction of 4-nitrophenol to 4-aminophenol with excess NaBH4 revealed that the catalyst with 2.2 nm Ru NPs exhibits the highest catalytic activity compared to samples with larger Ru NPs (2.9–3.2 nm). Moreover, this catalyst displayed extraordinary shelf-life in the aqueous solution (up to ten months) and excellent reusability in ten consecutive reactions with easy magnetic separation at each step which were assigned to its conformational rigidity at a constant pH. These characteristics as well as favorable environmental factors of the catalyst fabrication, make it promising for nitroarene reduction.