Dinuclear Molybdenum Complexes Research Articles

Dinuclear Molybdenum(VI) Complexes Based on Flexible Succinyl and Adipoyl Dihydrazones

A series of molybdenum(VI) complexes with aryl-functionalized alkyl dihydrazones was prepared by the reaction of [MoO2(acac)2] and the appropriate dihydrazone in methanol. Their solid-state structures were elucidated via single-crystal X-ray diffraction (SC-XRD) and Fourier-transform infra-red (FTIR) spectroscopy, while the thermal stability of compounds was inspected by combined thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) experiments. The behaviour of complexes in DMSO-d6 solution was explored by nuclear magnetic resonance (NMR). The relevant data show that all complexes are dinuclear, with dihydrazones acting as ditopic hexadentate ligands. The in vitro cytotoxic activity of the prepared molybdenum(VI) complexes was evaluated on THP-1 and HepG2 cell lines, while their antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Moraxella catarrhalis bacteria. The majority of compounds proved to be non-cytotoxic, while some exhibited superior antibacterial activity in comparison to dihydrazone ligands.

Mechanism, Stereoselectivity, and Role of O2 in Aza-Diels-Alder Reactions Catalyzed by Dinuclear Molybdenum Complexes: A Theoretical Study.

The aza-Diels-Alder-type reaction between imines and functionalized alkenes is one of the most versatile approaches to obtain piperidine derivatives. When using the Lewis acid [Mo2(OAc)4] (CAT) as a catalyst, it was found that the activation of CAT by O2 was essential for an efficient reaction. In this paper, the mechanism and stereoselectivity of the aza-Diels-Alder reaction between aromatic acyl hydrozones 1 and Danishefsky diene 2 under uncatalyzed and catalyzed (CAT not activated by O2 and CAT activated by O2) conditions have been studied by density functional theory (DFT) calculation. The results show that the uncatalyzed reaction is difficult to proceed at room temperature due to the high energy barrier. The CAT not activated by molecular oxygen has catalytic activity but not too much. When CAT is activated by O2, CATO2 may be the correct catalytic species, which results in a dramatic increase of reaction activity. The reaction mechanisms with/without the catalyst are different. The uncatalyzed reaction is concerted for both the endo and exo pathways. For the CAT-catalyzed reaction, the endo pathway is concerted, but the exo pathway is nonconcerted and involves two steps. The endo product is the main product for the reaction catalyzed by CAT, while for reactions catalyzed by CATO1 and CATO2, the endo and exo products can be obtained. The reaction activity is directly correlated to the atomic charges of two coupling C atoms. Our work explains the experimental results, determines the structure of the O2-activated catalyst species, and provides predictions for the reaction activity and stereoselectivity controlling.

Molybdenum-Mediated N2 -Splitting and Functionalization in the Presence of a Coordinated Alkyne.

A new [PCCP]‐coordinated molybdenum platform comprising a coordinated alkyne was employed for the cleavage of molecular dinitrogen. The coordinated η 2‐alkyne was left unaffected during this reduction. DFT calculations suggest that the reaction proceeds via an initially generated terminal N2‐complex, which is converted to a dinuclear μ‐(η 1:η 1)‐N2‐bridged intermediate prior to N−N bond cleavage. Protonation, alkylation and acylation of the resulting molybdenum nitrido complex led to the corresponding N‐functionalized imido complexes. Upon oxidation of the N‐acylated imido derivative in MeCN, a fumaronitrile fragment was built up via C−C coupling of MeCN to afford a dinuclear molybdenum complex. The key finding that the strong N≡N bond may be cleaved in the presence of a weaker, but spatially constrained C≡C bond contradicts the widespread paradigm that coordinated alkynes are in general more reactive than gaseous N2.

Molybdenum complexes bearing pyrimidine-2-thiolato (pymS) and tertiary phosphine ligands

In this paper we report mono- and dinuclear molybdenum complexes containing doubly bridging pymS and tertiary phosphine ligands PFu 3 or P(OMe) 3. One-pot reaction between [Mo(CO) 3 (NCMe) 3 ] and pymSH in the presence of tris(2-furyl)phosphine (PFu 3 ) in THF at 50 ˚C gives the previously reported eight coordinate compound [Mo( к 2 -pymS) 4 ] ( 1) in 17% yield and two new compounds [Mo(CO) 4 (PFu 3 ) 2 ] ( 2 ) and [Mo 2 (CO) 4 (μ- к 2 -pymS) 2 (PFu 3 ) 2 ] ( 3 ) in 51 and 15% yields, respectively. A similar reaction involving P(OMe) 3 furnishes two mononuclear complexes [Mo(κ 2 -pyS) 2 (CO) 2 {P(OMe) 3 }] ( 4 ) and [Mo(CO) 4 {P(OMe) 3 } 2 ] ( 5 ) in 20 and 35% yields, respectively. Complexes 2 and 4 were characterized by single-crystal X-ray diffraction analysis in addition to IR, 1 H NMRand 31 P{ 1 H} NMR spectroscopic methods.

Cis‐Dioxo‐molybdenum(VI) Complexes with Diaminoguanidinium and Triaminoguanidinium Schiff Bases and Their Catalytic Application for Epoxidation of Cyclohexene

AbstractDiaminoguanidinium and triaminoguanidinium Schiff bases of 1,3‐bis(3,5‐di‐tert‐butyl‐2‐hydroxyphenylmethylideneamino)guanidine hydrochloride (H5saldagtBu2 ⋅ HCl) and tris(3,5‐di‐tert‐butyl‐2‐hydroxybenzylidene)‐triaminoguanidinium chloride (H5saltagtBu2 ⋅ HCl) are synthesized. Treatment of H5saldagtBu2 ⋅ HCl with Na2MoO4 ⋅ 2H2O or (NH4)6Mo7O24 ⋅ 4H2O under different molar ratios afforded mono‐ and di‐nuclear molybdenum(VI) complexes of [(MoO2)(MeOH)(H3saldagtBu2)] (1), [(MoO2)2(MeOH)2(HsaldagtBu2)] ⋅ 2DMF (2 ⋅ 2DMF), and [(MoO2)2(HsaldagtBu2)] ⋅ ‐[(MoO2)2(H2O)2(HsaldagtBu2)] (3). Interactions of H5saltagtBu2 ⋅ HCl with Na2MoO4 ⋅ 2H2O or (NH4)6Mo7O24 ⋅ 4H2O under different reaction conditions resulted mono‐, di‐, and tetra‐nuclear molybdenum(VI) complexes of [(MoO2)(MeOH)(H3saltagtBu2)] (4), [(MoO2)(H2O)(H3saltagtBu2)] (5), [(MoO2)2(H2O)(DMF)(HsaltagtBu2)] ⋅ 3DMF (6) (Ref [31]), and [(MoO2)4(DMF)2(HsaltagtBu2)2] ⋅ 2H2O (7 ⋅ 2H2O). Complexes 1–7 were characterized by IR, 1H NMR and UV/vis spectroscopies. Molecular structures of H5saltagtBu2 ⋅ MeOH, 1, 2 ⋅ 2DMF, 3–5 and 7 ⋅ 2H2O are confirmed by single crystal X‐ray diffraction ananlysis, which shows that the diaminoguanidinium and triaminoguanidinium Schiff bases are coordinated to the cis‐{MoO2}2+ moieties via ONN atoms to form five‐ and six‐membered rings, sharing one Mo−N bond. The catalytic properties of these cis‐dioxo‐molybdenum(VI) complexes for epoxidation of cyclohexene were also investigated.

Dinuclear Molybdenum(II) Complexes with Thioether Functionalized Silylamide Ligands

Treatment of molybdenum(II) acetate with thioether functionalized silylamides R2Si(NLi‐C6H4–2‐SR')2 leads to the formation of dinuclear MoII complexes [Mo2{R2Si(NC6H4‐2‐SR')2}2]. According to X‐ray crystal structure analyses the complexes [Mo2{Me2Si(NC6H4‐2‐SMe)2}2] and [Mo2{Ph2Si(NC6H4‐2‐SPh)2}2] comprise a Mo2‐unit which is coordinated by two μ‐κ‐N,N' silylamide ligands. The coordination sphere around the molybdenum atoms consists of two amide nitrogen atoms and two thioether sulfur atoms in a distorted square‐planar arrangement. The Mo‐Mo distances are 211.0(1) and 211.7(1) pm, resp. In the complex [Mo2{Ph2Si(NC6H4‐2‐SMe)2}2] the silyl amide units act as tetradentate κ‐N,N',S,S'chelating ligands and the Mo‐Mo distance is 218.6(1) pm.

Oxovanadium(V) and Dioxomolybdenum(VI) Complexes of Amide-Imine Conjugates: Structures, Catalytic and Antitumor Activities.

Three new amide-imine conjugates, namely [(E)-2-hydroxy-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide] (SALNP), [(E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)-2-hydroxybenzohydrazide] (SALSD), and [(E)-N'-(3-ethoxy-4-hydroxybenzylidene)-2-hydroxybenzohydrazide] (SALVN), derived by reacting 2-hydroxybenzohydrazide (SAL) with three different aldehyde, 2-hydroxynapthaldehyde, 4-(diethylamino)-2-hydroxybenzaldehyde, and 3-ethoxy-4-hydroxybenzaldehyde, respectively. Three mononuclear oxovanadium(V) and two μoxo-bridged dinuclear molybdenum(VI) complexes have been synthesized using SALNP and SALSD. Besides, SALVN is used to prepare oxovanadium(V) and dioxomolybdenum(VI) complexes. All five metal complexes along with three amide-imine conjugates are characterized by single crystal XRD analysis. Some of them have been explored as catalyst for oxidation of alkyl benzene and styrene. Antitumor activities of the metal complexes along with ligands have been studied on Dalton lymphoma (DL) and 2PK3 murine lymphoma cells.

Molecular Mimics of Heterogeneous Metal Phosphides: Thermochemistry, Hydride‐Proton Isomerism, and HER Reactivity

AbstractA new series of low‐valent dinuclear molybdenum complexes bearing phosphido or phosphinidene bridging ligands was synthesized as a structural model of heterogeneous metal phosphide catalysts. Addition of acid to a monocationic Mo2‐μ‐P complex results in phosphide protonation, affording a dicationic Mo2‐μ‐PH species. Alternatively, reaction of an isoelectronic Mo2‐μ‐P precursor with LiBEt3H gives a Mo2H‐μ‐P complex. Mixing these species, one bearing a Mo−H and the other a P−H bond, results in facile H2 production at room temperature.

Dinuclear MoV Complexes with Thiophenolate‐oxazoline Ligands: Synthesis, Characterization, and Exceptional Activity in Catalytic Olefin Epoxidation

The synthesis, characterization, and epoxidation catalysis of two neutral, dinuclear molybdenum(V) complexes [{MoO(Lx)(µ‐O)}2] (x = 1: 1; x = 2: 2) bearing S,N‐bidentate thiophenolate‐oxazoline ligands (L1, L2) are described. Both complexes are formed under reduction of the metal with formation of disulfides (L1)2 and (L2)2. Each Mo center is coordinated by one bidentate thiophenolate‐oxazoline ligand and one terminal and two bridging oxido ligands. The solid‐state structures of NaL2 and complex 1 were confirmed by single‐crystal X‐ray diffraction. The five‐coordinate nature of the molybdenum atoms in 1 and 2 leads to exceptionally high catalytic activities in the epoxidation of cyclooctene. The catalyst loading can be reduced to 0.001 mol‐% (10 ppm), with a turnover number (TON) of 85000 and a maximum turnover frequency (TOF) of 62000 h–1 for 1, and a TON of 87400 and a TOF of 107400 h–1 for 2. For cyclooctene, the catalyst solutions can be recycled multiple times without significant loss of activity; however, other substrates (styrene, 1‐octene, and limonene) showed conversions with lower selectivity. The fate of catalyst 1 was examined by stoichiometric addition experiments with tert‐butyl hydroperoxide, which resulted in the formation of benzenesulfonate‐oxazoline derivative HL3 and polyoxomolybdates.

Intriguing binding modes of tetradentate pyridoxal derivatives to molybdenum centre

The Schiff base pdxen ligands (H2py2en=N,N′-ethylenebis(pyridoxylideneimine) and H2py2pren=N,N′-prophylenebis(pyridoxylideneimine)) were found to form readily by the mechanochemical synthesis from their corresponding diamine and pyridoxal. Reduction of the Schiff bases with NaBH4 yielded reduced pdxan ligands (H2Rpy2en=N,N′-ethylenebis(pyridoxylamine) and H2Rpy2pren=N,N′-prophylenebis(pyridoxylamine)). A dinuclear molybdenum(VI) complex with the bridging pdxen ligand [{MoO2}2(μ-py2en)(OMe)2(MeOH)2]⋅3MeOH (1⋅3MeOH), and mononuclear complexes with the pdxen ligand [MoO2(py2pren)] (3), as well as with the pdxan ligands: [MoO2(Rpy2en)] (2) and [MoO2(Rpy2pren)] (4) were prepared and characterized. Significant differences in the coordination of the Schiff base ligands were found as a consequence of chain length and ligand flexibility. Complexes 1–4 were obtained either by the reaction of [MoO2(acac)2] or [Mo(CO)6] with the corresponding ligands. Crystal and molecular structures of complexes 1⋅3MeOH, 2 and 3 were determined by the single crystal X-ray diffraction method. All complexes were characterized by microanalysis, FT-IR, NMR, UV, thermogravimetric analysis and powder X-ray diffraction method.

Synthesis and Structures of Mono‐ and Dinuclear Molybdenum Complexes with Reduced α‐Diimine Ligands

The mononuclear molybdenum complex [Mo(HL)2] (1), Mo–Mo single‐bond compound [HLClMo(µ‐Cl)3MoHLCl] [2; Mo–Mo 2.832(7) Å], and Mo≡Mo triple‐bond compounds [Mo2Cl2(µ‐HL)2] [3; Mo–Mo 2.194(6) Å] and [Mo2Cl2(µ‐Cl)(µ‐HL)Cl2Na(THF)3] [4; Mo–Mo 2.167(2) Å] have been synthesized by the reaction of HL {HL = [(2,6‐iPr2C6H3)NCH]2} with 0.5, 1, and 2 equiv. of MoCl5 and different amounts of Na metal. In the single‐bond compound 2, the α‐diimine ligand HL displays the normal chelating coordination mode. In contrast, the triple‐bond compounds 3 and 4 feature the less common bridging mode of α‐diimine ligands. Complexes 1–4 have been characterized by X‐ray diffraction, 1H and 13C NMR, IR spectroscopy, elemental analysis, and their electronic structures were studied by EPR and DFT computations.

Interplay between Theory and Experiment for Ammonia Synthesis Catalyzed by Transition Metal Complexes.

Nitrogen fixation is an essential chemical process both biologically and industrially. Since the discovery of the first transition-metal-dinitrogen complex in 1965, a great deal of effort has been devoted to the development of artificial nitrogen fixation systems that work under mild reaction conditions. However, the transformation of chemically inert dinitrogen using homogeneous catalysts is still challenging because of the difficulty in breaking the strong triple bond of dinitrogen, and a very limited number of transition metal complexes have exhibited the catalytic activity for the direct transformation of dinitrogen into ammonia with low turnover numbers. To develop more effective nitrogen fixation systems, it is necessary to retrieve as much information as possible from the limited successful examples. Computational chemistry will provide valuable insights in the understanding of the reaction mechanisms involving unstable intermediates that are hard to isolate or characterize. We have been applying it for clarifying detailed mechanisms of dinitrogen activation and functionalization by transition metal complexes as well as for designing new catalysts for more effective nitrogen fixation. This Account summarizes recent progress in the elucidation of catalytic mechanisms of nitrogen fixation by using mono- and dinuclear molybdenum complexes, as well as cubane-type metal-sulfido clusters from a theoretical point of view. First, we briefly introduce experimental and theoretical contributions to the elucidation of the reaction mechanism of nitrogen fixation catalyzed by a mononuclear Mo-triamidoamine complex. Special attention is paid to our recent studies on Mo-catalyzed nitrogen fixation using dinitrogen-bridged dimolybdenum complexes. A possible catalytic mechanism is proposed based on theoretical and experimental investigations. The catalytic mechanism involves the formation of a monuclear molybdenum-nitride (Mo≡N) intermediate, as well as the regeneration of a dimolybdenum intermediate with the Mo-N≡N-Mo moiety. Comparison of the reactivity of di- and monomolybdenum complexes suggests that the dimolybdenum structure is essential for the catalytic activity. Synergy between the two Mo cores connected with a bridging N2 ligand is observed in the protonation of coordinated N2. Intermetallic electron transfer through the bridging N2 ligand reductively activates the coordinated N2 to be protonated. On the basis of the proposed catalytic mechanism, we used DFT calculations for rational design of dimolybdenum complexes serving as more effective catalysts for nitrogen fixation. Newly prepared dimolybdenum complexes with modified PNP-type pincer ligands exhibit greater catalytic activity than the original one.

The solid state structure of pyridinium hydrogen squarate

The solvothermal reaction of (PyH)[MoOBr4] (PyH+ = pyridinium cation, C5H5NH+) with squaric acid (H2Sq = 3,4-dihydroxy-3-cyclobutene-1,2-dione, H2C4O4) in pyridine has inadvertently afforded apart from a dinuclear molybdenum(V) complex with a coordinated squarato dianion another product, a simple pyridinium salt of hydrogen squarate, (PyH)(HSq) (HSq– = hydrogen squarate, HC4O4–). The salt crystallizes in the monoclinic space group P 21/c with a = 10.1061(9) Å, b = 11.0436(10) Å, c = 7.4497(7) Å and β = 103.188(2)°. Its solid state structure consists of infinite chains made of HSq– ions linked via strong O–H···O– hydrogen bonds. The corresponding O···O contacts are 2.5604(13) Å. The countercations, protonated pyridine molecules, are attached to these chains via N+–H···O– hydrogen bonds. The X-ray structure analysis has revealed stacking arrangements of both ions with short interplanar spacings. Weak intermolecular interactions of the π···π type between ions of the same charge and of the C–H···O type between the oppositely charged ions were shown to play an important role in their packing.

Synthesis, structure and bonding of new mono- and dinuclear molybdenum complexes containing pyridine-2-thiolate (pyS) and different P-donors

Three new molybdenum complexes have been synthesized from one-pot reactions between Mo(CO)3(NCMe)3 and pyridine-2-thiol (pySH) in the presence of different P-donors. Reaction with P(OMe)3 in MeCN at ca. 55°C gives Mo(CO)2[P(OMe)3](κ2-pyS)2 (1) and Mo(CO)4[P(OMe)3]2 (2). A similar reaction involving bis(diphenylphosphino)methane (dppm) furnishes the dinuclear species Mo2(CO)4(μ,κ2-pyS)2(κ2-dppm) (3) together with the mononuclear complexes Mo(CO)(κ2-pyS)2(κ2-dppm) (4) and Mo(CO)4(κ2-dppm) (5). With bis(diphenylphosphino)ethane (dppe) only the mononuclear complexes Mo(CO)(κ2-pyS)2(κ2-dppe) (6), Mo(CO)4(κ2-dppe) (7), and Mo(CO)3(κ1-dppe)(κ2-dppe) (8) resulted. Complexes 1, 3, and 6 have been characterized by single-crystal X-ray diffraction analyses and the bonding in 1 and 3 has been evaluated by density functional theory (DFT) calculations, optimized structures being discussed relative to the observed solid-state structures.

Synthesis of two novel dinuclear molybdenum(0) complexes of quinoxaline-2,3-dione: New precursors for preparation of α-MoO3 nanoplates

α-MoO3 nanoplates have been prepared through thermal decomposition of two novel organometallic molybdenum complexes, as new solid precursors, at 500°C for 2h. The two molybdenum complexes ([(Mo2(bipy)(CO)n(DQ)m]; where, DQ=quinoxaline-2,3-dione; n=2 or 4, m=2 or 3) were synthesized by reaction of Mo(CO)6, and DQ in presence of 2,2′-bipyridine in THF solvent at reflux temperature under atmospheric or reduced pressure. Interestingly, the crystallite size of the produced MoO3 nanoplates products (80.7 and 114nm) depended on the organic moiety content of the ignited solid precursor. The as-prepared products were characterized by means of elemental analysis, Fourier transform infrared spectroscopy (FT-IR), UV–Vis spectroscopy, thermal analysis (TGA), X-ray powder diffraction (XRD), Field emission electron microscopy (FESEM) and mass spectroscopy. The produced MoO3 nanoplates showed semiconducting properties by exhibiting optical band gab energy of 3.0 or 3.25eV.

Synthesis and characterization of tricarbonyl–molybdenum complexes bearing monoaza-trithia-macrocyclic ligands

Novel tricarbonyl–molybdenum complexes bearing monoaza-trithia-macrocyclic ligands (LXR), [Mo(CO)3(LXR)] (X=12 or 14, R=H), and [Mo(CO)3(L14Py)Mo(CO)4] have been synthesized to gain an understanding of the unique properties of macrocyclic ligands. X-ray structure analysis of [Mo(CO)3(L14H)] has revealed that intra- and intermolecular hydrogen bonds existed and these interaction regulated CO bond lengths. In addition, vibrational spectroscopy indicates that a specific hydrogen bonding interaction affects the strength of the binding of carbon monoxide molecules to the metal. In case of using L14Py, it is expected that dinuclear molybdenum complex was generated.

Synthesis and characterization of oxomolybdenum(V) dinuclear complexes with β-alanine, l-serine and dl-isoleucine

New dinuclear molybdenum(V) complexes of the general formula [Mo2O4(acac)2aa], where acac=acetylacetonato, aa=amino acid: β-alanine, l-serine or dl-isoleucine were obtained by the reaction of the dinuclear oxomolybdenum complex [Mo2O3(acac)4] with an amino acid in ethanol. Complexes were characterized by vibrational spectroscopy (IR, Raman) and thermal methods (TG/DSC). The crystal and molecular structures of [Mo2O4(acac)2(β-alanine)]·H2O (1), [Mo2O4(acac)2(l-serine)]·2C2H5OH·H2O (2) and [Mo2O4(acac)2(dl-isoleucine)] (3) were determined by single crystal X-ray diffraction. Powder diffraction data were analyzed for complexes [Mo2O4(acac)2(β-alanine)] and [Mo2O4(acac)2(l-serine)] whose single-crystal data were those of the solvates 1 and 2. The obtained complexes 1–3 are dinuclear with the {Mo2O4}2+ core. The crystal structures showed that the molybdenum atoms are octahedrally coordinated with one terminal oxo-oxygen, two bridging oxo-oxygen atoms, two oxygen atoms from the bidentate acetylacetonato ligand and one oxygen atom from the bridging carboxylato group of the corresponding amino acid. A common feature of all three complexes is formation of tubular 2D layers in 2 and puckered 2D layers in 1 and 3.

Charged dioxomolybdenum(VI) complexes with pyridoxal thiosemicarbazone ligands as molybdenum(V) precursors in oxygen atom transfer process and epoxidation (pre)catalysts

The reaction of [MoO2(acac)2] with hydrochloric salts of pyridoxal thiosemicarbazone ligands, H2L1–3·HCl, in dry methanol or acetonitrile resulted in the formation of the mononuclear complex [MoO2(HL1)(CH3OH)]Cl·1.5CH3OH (1a) or polynuclear complexes [{MoO2(HL1–3)}Cl]n (1–3) containing a different substituent on the nitrogen atom of the N-thioureide fragment: Ph (1 and 1a), Me (2) or H (3). New dinuclear molybdenum(V) complexes [Mo2O3(HL1–3)2]Cl2 (4–6) were obtained by oxygen atom abstraction from 1–3 with triphenylphosphine. All compounds were characterized by chemical analysis, IR spectroscopy, one- and two-dimensional NMR methods, TGA and in selected cases by DSC measurements. In addition, the crystal and molecular structure of 1a was determined by single crystal X-ray diffraction. All molybdenum(VI) species were used as (pre)catalysts for olefin epoxidation under solvent-free conditions with a 0.05% Mo loading versus olefin.

Bis(μ2-η2:η2-2,4,6-trimethylbenzonitrile)bis[(N-isopropyl-3,5-dimethylanilido)molybdenum(III)](Mo—Mo)

The title compound, [Mo2(C11H16N)4(C10H11N)2], is a dinuclear molybdenum complex with a formal metal–metal bond [Mo⋯Mo separation = 2.5946 (8) Å], four anilide-type ligands and two bridging mesityl nitrile groups. There are two inversion symmetric mol­ecules in the unit cell (an inversion center is localized at the mid-point of the Mo—Mo bond), each with approximate non-crystallographic C 2h symmetry. The mol­ecules contain disordered isopropyl and 3,5-C6H3Me2 groups on different anilido ligands; the major component having an occupancy of 0.683 (7). The complex was obtained in low yield as the product from the reaction between the bridging pyrazine adduct of molybdenum tris­-anilide ([μ2-(C4H4N2){Mo(C11H16N)3}2]) and mesityl nitrile with a loss of one anilido ligand.

Synthesis and Structural Characterization of a Dimolybdenum Complex Bridged by the Hydroxymethylphenylphosphinate Ligand

AbstractHydroxymethylphenylphosphinic acid, 1 was synthesized and structurally characterized by single crystal X-ray diffraction. Ligand 1 crystallized in the monoclinic P2 1 space group with two molecules comprising the unit cell and cell dimensions a = 7.5587(13) A, b = 5.9019(8) A, c = 8.808(3) A and β = 90.90(2)°. Molecules were linked up by hydrogen bonding involving all three oxygen atoms of 1 resulting in 2-dimensional sheets. Reacting 1 with MoO 2 Cl 2 in a mixture of ethanol and dichloromethane afforded the dinuclear molybdenum complex Mo 2 O 4 Cl 2 [(HOCH 2 )PhPOO] 2 , 2 where the two molybdenum atoms were bridged by the phosphinate ligand. Complex 2 crystallized in the P2 1/C space group as a dietherate with a = 9.208(3) A, b = 14.353(4) A, c = 12.805(4) A and β = 98.64(3)° and contained terminal O and Cl atom disorder. The two crystallographically identical molybdenum centers are in distorted octahedral environments. Complexes were analyzed by IR, 31 P NMR and X-ray crystallography.Graphical AbstractThe reaction of hydroxymethylphenylphosphinic acid with MoO 2 Cl 2 in a mixture of ethanol and dichloromethane afforded the dinuclear molybdenum complex Mo 2 O 4 Cl 2 [(HOCH 2 )PhPOO] 2 , 2 where the two molybdenum atoms were bridged by the phosphinate ligand.[IMAGE]