16065-87-5

Basic information

• Product Name: molybdenum(6+)
• CAS NO: 16065-87-5
• Molecular Formula: Mo
• Molecular Weight: 95.9367
• Mol File: 16065-87-5.mol

Chemical Properties

• CAS DataBase Reference: molybdenum(6+)(CAS DataBase Reference)
• NIST Chemistry Reference: molybdenum(6+)(16065-87-5)
• EPA Substance Registry System: molybdenum(6+)(16065-87-5)

Safety Data

• Hazardous Substances Data: 16065-87-5(Hazardous Substances Data)

Upstream product

• 18252-79-4 vanadium(V) ion 
• 14333-13-2 permanganate(VII) ion 
• 15377-81-8 hexaaquairon(III) 
• 108772-69-6 (Mo₃O₄(H₂O)9)⁽⁴⁺⁾ 
• 74353-85-8 {Mo3(μ3-O)(μ2-O)3(H2O)9}(4+) 

Downstream Products

• 22541-84-0 molydbenum⁽⁵⁺⁾ 
• 22537-50-4 tin(IV) 
• 21175-08-6 molybdenum(IV) 
• 919767-08-1 MoO₂(C₆H₅C(O)N(O)C₆H₅)2 

Relevant articles and documents

Electron transfer. 110. Oxidations of trinuclear aquomolybdenum(IV)

The trimeric cation of molybdenum(IV), Mo3O4(OH2)94+, (structure I) readily reacts with oxyhalogen species and metal-center oxidants in aqueous acid. Conversions are to Mo(VI), even with the oxidants in deficiency. Reductions of BrO3- and ClO3- are to the respective halide ions, whereas H5IO6 is reduced rapidly to IO3-, which is then reduced much more slowly. Kinetic patterns for oxidations by BrO3- and H5IO6 (rate law 6 in text) indicate that these reactions entail conversion of the reductant (pKA = 0.7 at μ = 2.0 M) into its conjugate base, which forms a 1:1 complex with both oxyhalogens. Oxidation by V(V) appears to utilize two paths with transition states differing by a single H+; an observed [V(V)]2 dependency points to reaction via an unusually reactive vanadium(V) dimer. Oxidation by Fe(III) is unobservably slow in HTos or HCl but is markedly accelerated by thiocyanate, suggesting a specific bridging role for Fe(III)-bound NCS-. Both (MoIV)3 and its anation product (MoIV)3-NCS are oxidized by FeNCS2+, and both paths require loss of two protons. Oxidation by Cr(VI) is seen to pass through a strongly absorbing intermediate (ε530 = 3 × 103 M-1 cm-1 in 1 M HTos), which decays unimolecularly (k = 1 × 102 s-1 at [H+] = 1.0 M). The behavior of this intermediate is consistent with its formulation as a complex of Cr(IV) associated with a partially oxidized molybdenum cluster (e.g. MoIVMoIVMoVI). Although all oxidations of (MoIV)3, by both 1e and 2e reagents, yield three MoVI's (a net change of six units), rates are generally determined by the initial redox act. Succeeding electron transfers and breakup of partially oxidized Mo clusters proceed too rapidly to affect the kinetic picture.

Kinetics of Redox Reactions between Complexes of Molybdenum and Iron: The Oxidation of Iron(II) by Molybdenum(VI) and of 3+ by 3+

In 8 mol dm-3 hydrochloric acid MoVI is reduced to MoV by FeII.Under these conditions, MoVI exists predominantly as MoO2Cl2 and MoV as MoOCl52-.Spectrophotometric studies indicate that the stoicheiometry of the reaction is exactly 1:1 and that the equilibrium is far to the side of the products.Studies of the kinetics of this redox process by stopped-flow techniques revealed that the rate of reaction is first-order in each reactant and that the second-order rate constant is k=(3.6+/-0.1) x 103 dm3 mol-1 s-1 (20 deg C, 8 mol dm-3 HCl).The mechanism of the reaction is not known, but a chloride-bridged inner-sphere process appears plausible.Equilibrium studies of the oxidation of 3+ by Fe3+ in 1 mol dm-3 p-toluenesulphonic acid (Hpts) indicate that a dimeric MoV species, Mo2O42+, is the first stable product.With an excess of Fe3+, this species is oxidized to MoVI.In kinetic studies with Fe3+ in excess, three processes could be observed: (a) the disappearance of Mo3+, (b) the formation of Mo2O42+, and (c) the disappearance of Mo2O42+.Process (a) occurs in the ms range.It is described by the equation -d3+>/dt=k13+>3+>, with k1=(1.30+/-0.05) x 103 dm3+ mol-1 s-1 (25 deg C, 1 mol dm-3 Hpts), and obviously proceeds by an outer-sphere mechanism.Steps (b) and (c) overlap strongly (seconds to minutes).The measured reaction curves for (b) and (c) can be satisfactorily described by two superimposed exponentials of rather similar time constants.The formation of Mo2O42+ from the products of the fast step is discussed in terms of a mechanism which is in approximate though not complete agreement with the experimental data.The second-order rate constant for the oxidation of the intermadiate Mo2O42+ by FeIII which has been evaluated from the reaction curves agrees well with that of a previous study in which Mo2O42+ was oxidized directly.

Kinetics of oxidation of simple complexes of molybdenum(IV) and -(V) by iron (III)

The kinetics of the oxidation of the dimer Mo(V) cation Mo2O42+ by Fe(H2O)63+ and Fe(phen)33+ in aqueous solution have been studied at 25 °C, ionic strength I = 2.0 M (NaClO4), by conventional spectrophotometry. In both systems the rate of reaction is first order in reductant and oxidant and thus indicates that the first electron-transfer step is rate determining for the overall process. With the Fe(III) aquo complex as oxidant, the predominant pathway involves a hydroxo species, probably Fe(OH)2+, which reacts with a second-order rate constant kFeOH = 1.3 × 103 M-1 s-1, presumably by an inner-sphere mechanism. Oxidation by Fe(H2O)63+ is much slower, kfe ≤ 0.2 M-1 s-1. The reaction of Fe(phen)33+ with Mo2O42+ is expected to proceed by an outer-sphere path; the rate constant of this process is kFePh = 13 M-1 s-1. The mechanism of the (outer-sphere) oxidation of the (μ-S)2Mov complex Mo2O2S22+ by Fe(phen)33+ is more complicated, involving either a change in the rate-determining step or the appearance of a non-steady-state intermediate. The initial slopes of the reaction curves yield for the rate of the first electron-Transfer step k = 0.4 or 0.8 M-1 s-1, respectively, depending on the interpretation (25 °C, 1 M HClO4, I = 1.0 M). The results reveal that Mo2O2S22+ is a less efficient reducing agent than Mo2O42+. The oxidation of the trimeric Mo(IV) species Mo3O44+ by Fe(phen)33+ is characterized by a rate-determining first electron-transfer step (outer sphere) with k = 51 M-1 s-1 in 1 M HCl, I =2.0 M (NaCl). Due to coordination of Cl- to the Mo(IV) cation, the rate in the chloride solution is much higher than that in a noncomplexing medium.

Kinetic investigation of the cerium(IV) oxidation of the bis(μ-oxo)bis(oxomolybdenum(V)) ion

The reaction between bis(μ-oxo)bis(oxomolybdenum(V)), Mo2O42+, and Ce(IV) has been studied in acidic perchlorate media via stopped-flow techniques. The reaction is rapid and quantitative, and the stoichiometry corresponds to Mov2 + 2Ce(IV) →H+ MoVI2 + Ce(III). The observed rate law for the reaction for [Mo4O42+] > [Ce(IV)] is -d[Ce(IV)]/2dt = k2[Mo2O42+] [Ce(IV)], where k2 = k2hKh/([H+] + Kh). The rate constant, k2h, was found to be 2.73 X 104 M-1 s-1 and Kh = 0.46 M (μ = 2.0 M, T = 25.0°C). The observed rate constant was unaffected by added products or Cl- (-3) but increased slightly with ionic strength. Evidence for an ion pair formed between the aquomolybdenum(V) dimer and Ce(IV) is presented.