Mo Complexes Research Articles

Molybdenum Induced Modifications in the Quantum Capacitance of Graphene‐Based Supercapacitor Electrodes: First‐Principle Calculations

Herein, spin‐polarized calculation is performed based on density‐functional theory in the frame of generalized gradient approximation to examine the quantum capacitance (CQ) and surface charge storage of graphene(G)‐based supercapacitor electrodes modified with molybdenum, sulfur, nitrogen, and monovacancy. In total, 15 electrode models, including graphitic doping, monovacancy doping, and Mo adsorption on pristine and single‐vacancy graphene structures are analyzed. In the results, it is demonstrated that vacancy defects and N/S/Mo doping enhances the CQ of graphene. Among all configurations, pyrrolic‐S (d1S) shows the lowest CQ performance due to few states at the Fermi level. Electrodes with Mo adsorption exhibit the highest CQ, particularly when Mo is adsorbed at the top site of graphene. However, formation and adsorption energy calculations suggest that Mo is more likely to adsorb at hollow sites. Optimally, Mo can be most effectively utilized by loading it onto vacancy or N/S‐decorated vacancy sites. The significant contribution of Mo's 4dz2 and 4s states to CQ, along with the charge‐redistribution around the Mo complexes, may facilitate proton‐coupled electron transfer to enhance pseudocapacitance. In these findings, valuable insights into designing high quantum capacitance of 2D materials with electroactive sites for improved energy storage are offered.

Fe3O4@ATA‐Mo Complex as a Suitable and Reusable NanoCatalyst for Solvent‐Free Synthesis of Dihydropyrimidinones

AbstractFe3O4 nanoparticles were synthesized and functionalized by molybdenum aurintricarboxylic acid. Complex physicochemical characteristics of the catalyst were investigated by various methods such as infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, vibrating sample magnetometry, and X‐ray energy diffraction spectroscopy. The results confirmed the spherical morphology, nanoscale size, magnetic properties, and the presence of the desired elements in the synthesized catalyst. Efficiency of the catalyst was determined by the synthesis of dihydropyrimidinone derivatives via Biginelli condensation. Under optimal conditions, a variety of dihydropyrimidinones derivatives were synthesized with good and excellent yields. The magnetic nature of the catalyst, easy separation of the reaction mixture, and catalyst reusability are the advantages of this work. The use of solvent‐free conditions is the other advantage.

A Transient Iron Carbide Generated by Cyaphide Cleavage.

Despite their potential relevance as molecular models for industrial and biological catalysis, well-defined mononuclear iron carbide complexes are unknown, in part due to the limited number of appropriate C1 synthons. Here, we show the ability of the cyaphide anion (C≡P-) to serve as a C1 source. The high spin (S = 2) cyaphide complex PhB(tBuIm)3Fe-C≡P (PhB(tBuIm)3- = phenyl(tris(3-tert-butylimidazol-2-ylidene)borate) is readily accessed using the new cyaphide transfer reagent [Mg(DippNacNac)(CP)]2 (DippNacNac = CH{C(CH3)N(Dipp)}2 and Dipp = 2,6-di(iso-propyl)phenyl). Phosphorus atom abstraction is effected by the three-coordinate Mo(III) complex Mo(NtBuAr)3 (Ar = 3,5-Me2C6H3), which produces the known phosphide (tBuArN)3Mo≡P along with a transient iron carbide complex PhB(tBuIm)3Fe≡C. Electronic structure calculations reveal that PhB(tBuIm)3Fe≡C adopts a doublet ground state with nonzero spin density on the carbide ligand. While isolation of this complex is thwarted by rapid dimerization to afford the corresponding diiron ethynediyl complex, the carbide can be intercepted by styrene to provide an iron alkylidene.

A DFT Analysis of Structural and Electronic Features of [Mo(CO)6‐n(SiX)n] (n=1, 2 and 3, and X=O, S, Se and Te) Complexes

AbstractDFT was used to analyze the molecular and electronic structures of the mono, di‐ and tri‐substituted isomers of [Mo(CO)6‐n(SiX)n] (where, X=O, S, Se, Te) and they were compared to the Mo(CO)6 complex. The total energy of all the complexes indicates that the trans isomer is slightly more stable than the cis isomer, but the stability of the fac and mer isomers is comparable. The HOMO‐LUMO energy gap of the complexes was determined and it indicated that the energy gap of the newly designed complexes is smaller than that of the parent complex Mo(CO)6 (1), ranging from 3.45–5.08 eV for the complexes 2–21. The FMO analysis of 2–21 showed that they are more reactive than complex 1. Insights on the bonding nature of these complexes are provided by the NPA, NBO, and EDA studies. The bond contribution from the Si atom in the Mo−Si bond is greater than that from the Mo atom, based on the NBO study. However, the C atom contributes more to the Mo−CO bond as well. Atomic charges on the Mo atom have a higher negative charge and the Si atom shows a positive charge in all the complexes. This study provides valuable information about the isolobal and isoelectronic nature of different substitutions of Si−X bonds at different positions instead of CO molecule in [Mo(CO)6].

Tuning the Structures of Amide‐Imine Conjugates for Sequential Optical Recognition of Mo(VI) and AsO2− Ions

AbstractTwo amide‐imine conjugates where amide is synthesized by reacting hydrazine with 4‐hydroxybenzoic acid and subsequently condensed with 2‐hydroxy naphthalene‐1‐carbaldehyde (m1) and 2‐hydroxy benzaldehyde (m2), selectively detects Mo(VI) at nano molar level via change in emission characteristics. The interactions have been authenticated from single crystal X‐ray structures of resulting Mo(VI) complexes (Mo1 and Mo2). Further, Mo1 selectively interacts with AsO2− via formation of H‐bond that facilitates its detection through change of emission characteristics. The binding constant of Mo1 for AsO2− is 1.02×105 M−1/2. The TCSPC studies support the interaction of Mo1 with AsO2−. The probe‐analyte interaction has also been established by different spectroscopic techniques like 1H NMR, ESI‐MS, FTIR and Jobs experiment. Theoretical DFT studies justifies the reason behind the interaction and support experimental spectroscopic findings. Notably, the sequential fluorescence recognition of Mo(VI) and AsO2− by m1 have been explored to construct a logic gate.

Dimolybdenum (II,II) paddlewheel complexes bearing non-steroidal anti-inflammatory drug ligands: Insights into the chemico-physical profile and first biological assessment

Multinuclear complexes are metal compounds featured by adjacent bound metal centers that can lead to unconventional reactivity. Some M2L4-type paddlewheel dinuclear complexes with monoanionic bridging ligands feature promising properties, including therapeutic ones. Molybdenum has been studied for the formation of multiple-bonded M2+ compounds due to their unique scaffold, redox, and spectroscopic properties as well as for applications in several fields including catalysis and biology. These latter are much less explored and only sporadic studies have been carried out. Here, a series of four dimolybdenum (II,II) carboxylate paddlewheel complexes were synthesized using different Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) as ligands. The reaction of (NH4)5[Mo2Cl9]·H2O with the selected NSAIDs in methanol produced the complexes Mo2(μ-O2CR)4 where RCO2 is ibuprofen (1), naproxen (2), aspirin (3) and indomethacin (4). The products were obtained in good yields and extensively characterized with integrated techniques. Stability and solution behaviour were studied using a mixed experimental and computational approach. Finally, the biological activity of 1 and 3 (i.e. the most reactive and the most stable compounds of the series, respectively) was preliminarily assessed confirming the disassembling of the molecules in the biological milieu. Overall, some very interesting results emerged for these unconventional compounds from a mechanistic point of view.

Low Mo mobility during the laterization of ultramafic bedrock: Evidence from the East Sulawesi Ophiolite, Indonesia

Mo (isotope) cycling during the chemical weathering of ultramafic bedrock remains poorly quantified, mainly as a result of the analytical challenges caused by low Mo concentration and complex matrix effects in these rock types. Here, we utilize an improved chemical separation protocol that enables the extraction of Mo while reducing Ru and Fe matrix effects. We apply this method to lateritic weathering profiles developed over ultramafic bedrock in a high-intensity tropical weathering regime. The Mo concentrations in the laterite samples are higher (0.022 to 0.58 μg·g−1) than those of the peridotite bedrock (0.006 to 0.021 μg·g−1). The concentration-weighted average δ98Mo of the laterite profiles is −0.05‰ (n = 17), which is slightly higher but very close to the average δ98Mo of the peridotite bedrock (0.17 ± 0.21‰; 2SD; n = 5). Weakly-laterized samples show somewhat low δ98Mo with a minimum of −1.03‰ and Δ98Molaterite-bedrock up to −0.86‰, possibly as a result of preferential adsorption of liberated light Mo onto Fe (oxyhydr)oxides. In contrast, strongly-laterized samples show an overall Mo concentration gain and a slight isotopic shift towards higher bulk δ98Mo, with a maximum δ98Mo of +0.12‰ and Δ98Molaterite-bedrock up to +0.42‰. This likely reflects the re-scavenging of Mo released from weakly-laterized horizons to the ubiquitous Fe (oxyhydr)oxides, with potential superimposition of additional heavy Mo from atmospheric and/or groundwater input. Overall, this suggests a small contribution of dissolved Mo derived from ultramafic bedrock weathering in tropical settings to the aquatic environment.

Synthesis and Structural Studies of peri-Substituted Acenaphthenes with Tertiary Phosphine and Stibine Groups.

Two mixed peri-substituted phosphine-chlorostibines, Acenap(PiPr2)(SbPhCl) and Acenap(PiPr2)(SbCl2) (Acenap = acenaphthene-5,6-diyl) reacted cleanly with Grignard reagents or nBuLi to give the corresponding tertiary phosphine-stibines Acenap(PiPr2)(SbRR') (R, R' = Me, iPr, nBu, Ph). In addition, the Pt(II) complex of the tertiary phosphine-stibine Acenap(PiPr2)(SbPh2) as well as the Mo(0) complex of Acenap(PiPr2)(SbMePh) were synthesised and characterised. Two of the phosphine-stibines and the two metal complexes were characterised by single-crystal X-ray diffraction. The peri-substituted species act as bidentate ligands through both P and Sb atoms, forming rather short Sb-metal bonds. The tertiary phosphine-stibines display through-space J(CP) couplings between the phosphorus atom and carbon atoms bonded directly to the Sb atom of up to 40 Hz. The sequestration of the P and Sb lone pairs results in much smaller corresponding J(CP) being observed in the metal complexes. QTAIM (Quantum Theory of Atoms in Molecules) and EDA-NOCV (Energy Decomposition Analysis employing Naturalised Orbitals for Chemical Valence) computational techniques were used to provide additional insight into a weak n(P)→σ*(Sb-C) intramolecular bonding interaction (pnictogen bond) in the phosphine-stibines.

Ligand‐promoted dehydrogenative coupling of γ‐/β‐amino alcohols with ketones to N‐heterocycles via molybdenum catalysts

Molybdenum‐based efficient and broadly applicable catalytic system is presented for the dehydrogenative coupling of γ‐/β‐amino alcohols with ketones. In particular, complex Mo(CO)6 in combination with Xantphos and t‐BuOK as base provides direct synthesis of structurally diverse quinoline, pyridine, and pyrrole compounds (total 55 examples) with isolated yields up to 92%. Low catalyst loading, cost‐effective, and high catalytic activities with high tolerance to stand with diverse functional groups are additional features of these molybdenum catalysts exhibiting high efficacy to replace the precious metal catalysts such as ruthenium and iridium. Furthermore, the DFT and experimental studies were explored for the reaction mechanism which can assist in broadening the scope of the molybdenum catalysts for different transformation reactions.

Photocatalytic Degradation and Anticancer Activity of Green Synthesized Molybdenum Nanoparticles for Inhibiting the Cervical Cancer Cells

This work reports the synthesis of molybdenum nanoparticles (Mo NPs) through green routes using horse gram seed extracts and characterized by GC-MS, electronic (UV-visible) spectroscopy, IR, XRD and SEM techniques. Their potent applications as in vitro anticancer agent against HeLa cell lines and photocatalytic degradation of methyl orange (MO) and methyl violet (MV) dyes were also evaluated. The anti-malignant properties of Schiff base ligands [2-fluorobenzaldehyde semicarbazone (L1H) and 2-fluorobenzaldehyde thiosemicarbazone (L2H) with molybdenum metal precursor [dioxobis(2,4-pentanedionato)molybdenum] were also explored and their Mo complexes after conversion into nano form as both ligands, L1H and L2H approve their binding property based on molecular docking studies.

Molybdenum Catalyzed Acceptorless Dehydrogenation of Alcohols for the Synthesis of Quinolines

AbstractThe first molybdenum triazolylidene complexes catalyzing the atom‐economical synthesis of quinolines through acceptorless dehydrogenative coupling of alcohols is reported. A new family of Mo(0) complexes bearing chelating bis‐1,2,3‐triazolylidene, pyridyl‐1,2,3‐triazolylidene, and bis‐triazole ligands have been prepared and applied as catalysts for the synthesis of quinolines. Interestingly, Mo complexes bearing bis‐1,2,3‐triazolylidene ligands with alkyl groups (Et, n‐Bu) displayed superior catalytic activities than those containing aryl substituents on the triazolylidene rings. Control experiments corroborated that the catalytic reaction involves the dehydrogenation pathway.

To Split or Not to Split: [AsCCAs]-Coordinated Mo, W, and Re Complexes and Their Reactivity toward Molecular Dinitrogen.

Molybdenum, tungsten, and rhenium halides bearing a 2,2'-(iPr2As)2-substituted diphenylacetylene ([AsCCAs], 1-As) were prepared and reduced under an atmosphere of dinitrogen in order to activate the latter substrate. In the case of molybdenum, a diiodo (2-As) and a triiodo molybdenum precursor (5) were equally suited for reductive N2 splitting, which led to the isolation of [AsCCAs]Mo≡N(I) (3-As) in each case. For tungsten, [AsCCAs]WCl3 (6) was reduced under N2 to afford {[AsCCAs]WCl2}2(N2) (7), which is best described as a dinuclear π8δ4-configured μ-(η1: η1)-N2-bridged dimer. Attempts to reductively cleave the N2 unit in 7 did not lead to the expected tungsten nitride (8), which had to be prepared independently via the treatment of 7 with sodium azide. To arrive at a π10δ4-configured N2-bridged dimer in a tetragonally distorted ligand environment, [AsCCAs]ReCl3 (9) was reduced in the presence of N2. As expected, a μ-(η1: η1)-N2-bridged dirhenium species, namely, {[AsCCAs]ReCl2}2(N2) (10), was formed, but found to very quickly decompose (presumably via loss of N2), not only under reduced pressure, but also upon irradiation or heating. Hence, an alternative synthetic route to the originally envisioned nitride, [AsCCAs]Re≡N(Cl)2 (11), was developed. While all the aforementioned nitrides (3-As, 8, and 11) were found to be fairly robust, significantly different stabilities were noticed for {[AsCCAs]MCl2}2(N2) (7 for M = W, 10 for M = Re), which is ascribed to the electronically different MN2M cores (π8δ4 for 7 vs π10δ4 for 10) in these μ-(η1: η1)-N2-bridged dimers.

Phosphorescent fac-Bis(triarylisocyanide) W(0) and Mo(0) Complexes.

Homoleptic W(0) and Mo(0) complexes containing bis(triarylisocyanide) ligands with bulky substituents were synthesized and spectroscopically characterized. Crystallographically determined structures revealed that these complexes are hourglass-like in shape with the tridentate ligands adopting a facial coordination mode to the metal center. These complexes luminesce in fluid solutions and in the solid state. Typically in toluene at 298 K, the two W(0) complexes display the emission maximum (lifetime and quantum yield) at 591 nm (0.83 μs and 0.35) and 628 nm (1.04 μs and 0.39), and similarly, the two Mo(0) complexes display it at 575 nm (0.54 μs and 0.15) and 617 nm (0.56 μs and 0.23). DFT and TDDFT calculations indicated that the low-energy absorption bands of the W(0) and Mo(0) complexes could be metal-to-ligand charge transfer (MLCT) transitions in nature. These complexes exhibited a reversible M+/0 redox couple at -0.70 and -0.63 V vs Fc+/0 for the W(0) complexes and -0.86 and -0.67 V for the Mo(0) complexes. The excited-state reduction potentials were hence estimated to be -2.91 and -2.74 V vs Fc+/0 for the W(0) complexes and -3.10 and -2.81 V vs Fc+/0 for the Mo(0) complexes, indicating that they are potentially strong photoreductants.

Preparative and Catalytic Properties of MoVI Mononuclear and Metallosupramolecular Coordination Assemblies Bearing Hydrazonato Ligands.

A series of polynuclear, dinuclear, and mononuclear Mo(VI) complexes were synthesized with the hydrazonato ligands derived from 5-methoxysalicylaldehyde and the corresponding hydrazides (isonicotinic hydrazide (H2L1), nicotinic hydrazide (H2L2), 2-aminobenzhydrazide (H2L3), or 4-aminobenzhydrazide (H2L4)). The metallosupramolecular compounds obtained from non-coordinating solvents, [MoO2(L1,2)]n (1 and 2) and [MoO2(L3,4)]2 (3 and 4), formed infinite structures and metallacycles, respectively. By blocking two coordination sites with cis-dioxo ligands, the molybdenum centers have three coordination sites occupied by the ONO donor atoms from the rigid hydrazone ligands and one by the N atom of pyridyl or amine-functionalized ligand subcomponents from the neighboring Mo building units. The reaction in methanol afforded the mononuclear analogs [MoO2(L1-4)(MeOH)] (1a-4a) with additional monodentate MeOH ligands. All isolated complexes were tested as catalysts for cyclooctene epoxidation using tert-butyl hydroperoxide (TBHP) as an oxidant in water. The impact of the structure and ligand lability on the catalytic efficiency in homogeneous cyclooctene epoxidation was elucidated based on theoretical considerations. Thus, dinuclear assemblies exhibited better catalytic activity than mononuclear or polynuclear complexes.

Chemical and redox non-innocence in low-valent molybdenum β diketonate complexes: novel pathways for CO2 and CS2 activation.

The investigation of fundamental properties of low-valent molybdenum complexes bearing anionic ligands is crucial for elucidating the molybdenum's role in critical enzymatic systems involved in the transformation of small molecules, including the nitrogenase's iron molybdenum cofactor, FeMoco. The β-diketonate ligands in [Mo(acac)3] (acac = acetylacetonate), one of the earliest low-valent Mo complexes reported, provide a robust anionic platform to stabilize Mo in its +III oxidation state. This complex played a key role in demonstrating the potential of low-valent molybdenum for small molecule activation, serving as the starting material for the preparation of the first reported molybdenum dinitrogen complex. Surprisingly however, given this fact and the widespread use of β-diketonate ligands in coordination chemistry, only a very limited number of low-valent Mo β-diketonate complexes have been reported. To address this gap, we explored the redox behavior of homoleptic molybdenum tris-β-diketonate complexes, employing a tertiary butyl substituted diketonate ligand (dipivaloylmethanate, tBudiket) to isolate and fully characterize the corresponding Mo complexes across three consecutive oxidation states (+IV, +III, +II). We observed marked reactivity of the most reduced congener with heterocumulenes CE2 (E = O, S), yet with very distinct outcomes. Specifically, CO2 stoichiometrically carboxylates one of the β-diketonate ligands, while in the presence of excess CS2, catalytic reductive dimerization to tetrathiooxalate occurs. Through the isolation and characterization of reaction products and intermediates, we demonstrate that the observed reactivity results from the chemical non-innocence of the β-diketonate ligands, which facilitates the formation of a common ligand-bound intermediate, [Mo( tBudiket)2( tBudiket·CE2)]1- (E = O, S). The stability of this proposed intermediate dictates the specific reduction products observed, highlighting the relevance of the chemically non-innocent nature of β-diketonate ligands.

Reactivity of metal hydrides with CO2: going beyond formate with a high-valent cationic pentahydride Mo(vi) complex.

The cationic molybdenum pentahydride complex [MoH5(depe)2]+ (depe = 1,2-bis(diethylphosphino)ethane) is shown to undergo two consecutive reactions with carbon dioxide. In the initial, room-temperature process, classical insertion of CO2 into a metal-hydride bond is observed, resulting in the formation of the expected formate complex, [MoH2(HCOO)(depe)2]+. Further reactivity is triggered at temperature above 100 °C. Complete conversion into two new complexes is indeed observed, resulting from the formal cleavage of a C-O bond of carbon dioxide, [MoH(CO)2(depe)2]+ and [MoO(HCOO)(depe)2]+. Unprecedented in the absence of ligand assistance, such metal hydride reactivity has been comprehensively studied by a combination of experimental and computational means with the aim of elucidating the underlying mechanism that governs this process.

Molybdenum-catalyzed hydrogenation of carbon dioxide, bicarbonate, and inorganic carbonates to formates.

Herein, we report the hydrogenation of carbon dioxide to sodium formate catalyzed by low-valent molybdenum phosphine complexes. The 1,3-bis(diphenylphosphino)propane (DPPP)-based Mo complex was found to be an efficient catalyst in the presence of NaOH affording formate with a TON of 975 at 130 °C in THF/H2O after 24 h utilizing 40 bar (CO2 : H2 = 10 : 30) pressure. The complex was also active in the hydrogenation of sodium bicarbonate and inorganic carbonates to the corresponding formates. Mechanistic investigation revealed that the reaction proceeded via an intermediate formato complex.

Reactions of (mesityl)n(methyl)2-nsilylene complexes with pyridine-N-oxide (n = 1 and 0): formation of silanone complexes and a disiloxanyloxy complex.

Silanones (OSiR2), a heavier congener of ketones (R2CO), are highly reactive species that are readily converted to oligomeric siloxane (O-SiR2)n. Coordination of silanones to the transition-metal fragments to afford silanone-coordinated complexes is a reliable silanone stabilization method. Recently, our group reported the synthesis, structures, and reactivity of dimesityl-substituted silanone complexes Cp*(OC)2M{OSiMes2(L)}(SiMe3) (M = W, Mo, L: Lewis base, Cp*: η5-C5Me5, Mes: 2,4,6-Me3C6H2). Herein, to investigate the effect of substituents on the silicon atom during the formation of a silanone complex, we demonstrated the use of Mes and smaller Me groups. As a result, the formation of Mes(Me)-substituted silanone molybdenum complex Cp*(OC)2Mo{OSiMes(Me)(py)}(SiMe3) (5b, py: pyridine) was suggested, the silanone tungsten complex Cp*(OC)2W{OSiMes(Me)(DMAP)}(SiMe3) (4a, DMAP: 4-(dimethylamino)pyridine) was obtained, and a dimethyl-substituted disiloxanyloxy(dioxo) complex Cp*(O)2W(OSiMe2OSiMe3) (9) was formed. The reaction of 4a with PMe3 proceeded via the elimination of DMAP and migration of the SiMe3 group to the oxygen atom of the silanone ligand to afford Cp*(OC)2W(SiMes(Me)OSiMe3)(PMe3) (11a). The Mo complex Cp*(OC)2Mo(SiMes(Me)OSiMe3)(PMe3) (11b) was produced by the reaction of Cp*(OC)2Mo{SiMes(Me)}(SiMe3) (7b) with pyridine-N-oxide in the presence of PMe3.

Leveraging molybdenum sulfur compounds as catalysts for the synthesis of biobased poly(ethylene 2,5-furandicarboxylate) and recycling

Two safe dinuclear Mo complexes with non-rigid bidentate phosphinoyldithio formate ligands, differing in phosphorus substituents, were demonstrated for the first time to enable both synthesis and recycling of PEF.

Molybdenum(VI) complexes of N, N′-bis isatin diamine Schiff base: Synthesis and characterization

Schiff base ligand of N, N′-bis isatin diamine was synthesized from various diamine and isatin through condensation reaction in 1:2 molar ratio. Mo(VI) complexes of isatin-diamines were synthesized by the reaction between the sodium molybdate dehydrate and N,N' bis isatin diamines with the reflux method. The synthesized ligand and complexes were characterized using spectroscopic techniques. The FT-IR band of azomethine group at 1600- 1610 cm-1 indicated the formation of the ligand. The UV-vis spectra clearly indicated that the prepared complex is a genuine Mo(VI) with d0 electronic configuration. The formation of a coordination bond was revealed by the downfield chemical shift of the complex in the NMR data as compared to the ligand. The UV results were corroborated by molar conductance data, which demonstrated their non-electrolytic character. The experimental evidence primarily supported the synthesis of both ligands and corresponding Mo(VI) complexes. Bangladesh J. Sci. Ind. Res. 58(4), 201-208, 2023