New aqua rhenium oxocomplex; synthesis, characterization, thermal studies, DFT calculations and catalytic oxidations

Refat Mahfouz; Eida Al-Frag; M. Rafiq H. Siddiqui; Waed Z. Al-kiali; O. Karama

doi:10.1016/j.arabjc.2010.07.001

View/Download PDF

Buy Reprints

PDF

Translate this page into:

Original article

4 (

); 119-124

doi:

10.1016/j.arabjc.2010.07.001

New aqua rhenium oxocomplex; synthesis, characterization, thermal studies, DFT calculations and catalytic oxidations

Refat Mahfouz, Eida Al-Frag, M. Rafiq H. Siddiqui^*, Waed Z. Al-kiali, O. Karama

Department of Chemistry, College of Science, P.O. Box 2455, King Saud University, Riyadh 11451, Saudi Arabia

*Corresponding author rafiqs@ksu.edu.sa (M. Rafiq H. Siddiqui)

Received: 2010-7-3, Accepted: 2010-7-3, Published: 2010-01-01

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Available online 8 July 2010

Abstract

The aqua rhenium oxocomplex [ReO(OH)(H₂O)₄]²⁻ (1) has been prepared and characterized by spectroscopy, thermogravimetry, and elemental analysis and its reactivity towards triphenylphosphine has been evaluated. Complex (1) acts as a catalyst precursor in the presence of molecular oxygen for the oxidation of PPh₃ to OPPh₃. This proceeds through complex intermediates like [Re(PPh₃)_n]³⁺ (2), and [ReO(PPh₃)_n]³⁺ (3). The newly prepared complex (1) was also employed as catalyst for catalytic oxidation of cyclohexane. The geometry of [ReO(OH)(H₂O)₄]²⁻ has also been optimized in the singlet state by the DFT method with B3LYP level of theory.

Keywords

Rhenium

Complexes

Catalysis

Oxidation

DFT calculations

Show Related Articles from PubMed

1 Introduction

A major focus of the contemporary interest in the chemistry of the Group VII congener technetium and rhenium reflects the applications of ^99mTc and ¹⁸⁶Re or ¹⁸⁸Re in radiodiagnosis and radiotherapy, respectively (Jurisson et al., 1993; Deutsch et al., 1986; Chi et al., 1994 ). The nuclear properties of ^99mTc (t_1/2 = 6 h, γ = 140 keV) are ideal for diagnostic imaging, while the β-emitting isotopes ¹⁸⁶Re and ¹⁸⁸Re (t_1/2 = 90.64 h, E_max = 1.1 MeV, t_1/2 = 17 h, E_max = 2.1 MeV, respectively) are promising candidates for therapeutic applications (Ehrhardt et al., 1990). Rhenium (V) complexes comprise a prominent class of compounds in radiopharmaceutical chemistry. The oxidation state V of rhenium is easily stabilized by a large variety of ligands and it is easily obtained from the reduction of perrhenate (Machura, 2005). A distinctive feature of the most stable Re (V) complexes is the existence of multiple bonds to sulfur, nitrogen and especially oxygen (Davison and Jones, 1982; Blower et al., 1986). There is a considerable interest in the chemistry of inorganic compounds containing an oxygen atom that is multiply bonded to a transition metal in a high oxidation state. These compounds can transfer an oxygen atom to reactants such as phosphines, sulfides and alkenes. For many years they have been the center of interest to those scientists engaged in basic research and to those trying to employ these complexes in catalytic processes. Oxygen atom transfer chemistry has been applied in various reactions of industrial and biological importance, including olefin epoxidation and biomimicking catalysis by cytochrome (Machura and Kusz, 2008). The chemistry of oxorhenium complexes arouses particular interest on these compounds. The oxidation of tirphenylphosphine to triphenylohosphine oxide has attracted much interest due to its relevance to oxygen atom transfer reaction catalyzed by cytochrome P-450 oxidase (Taqui Khan et al., 1986). The rhenium aqueous compounds are highly important as they are considered as a prerequisite in the design of new compounds by substituting reactions in addition to their catalyzed oxidization.

In the present work, we report the synthesis and characterization of [ReO(OH)(H₂O)₄]S₂O₈ (1), as well as new Re complex derivatives, [Re(PPh₃)₅]³⁺ (2) which has been prepared by reduction of 1 with PPh₃ in the ethanolic medium. Further pharmacological and radiochemical studies of these complexes are under investigation.

2 Experimental

2.1

2.1 General procedure

All reactions were performed in air in reagent-grade solvents, all chemical and solvents were of reagent grade and used without further purification.

FT-IR spectra were recorded on a Perkin–Elmer FT-IR Spectrometer “Spectrum 1000” in the spectra range 4000–400 cm⁻¹ with the samples in the form of KBr pellets. Electronic Spectra were measured on a UV–Vis Beckman Du-70 Spectrometer in the range 800–200 nm. ¹H NMR, proton decoupled ¹³C and ³¹P NMR spectra were obtained at room temperature in DMSO d6 or CD₃OD using a JEOL Eclipse400 NMR using TMS for ¹H and ¹³C and 85% H₃PO₄ for ³¹P {¹H} as external standards. Elemental analysis (H) was preformed on a Perkin–Elmer C H N-2400 analyzer. The thermal analysis was carried out using a Perkin–Elmer thermogravimetric analyzer TGA7 in nitrogen atmosphere. The % weight loss was measured from the ambient temperature up to 900 °C at a heating rate of 10 °C/min. X-ray diffraction patterns of the complex were recorded using a X-ray diffractometer system XRD JDX-3530 with Cu-target.

2.2

2.2 Synthesis of [ReO(OH)(H₂O)₄]S₂O₈ (1)

Aqueous solution of Na₂S₂O₆ (250 mg, 1 mmol) was added dropwise to the stirred solution of NH₄ReO₄ (526 mg, 2 mmol) in water. The reaction was initially refluxed at 70 °C for up to 2 h and then stirred for 24 h at room temperature. The solution was concentrated by rotary evaporation. The crystals of [ReO(OH)(H₂O)₄]S₂O₈ were formed overnight. Yield: 77%.

IR of 1 (KBr, cm⁻¹): 996 s (1055) (ν (Re⚌O)); 3562 s (3793.3) (ν_str.antisym (OH)); 3474 s (ν_str.sym (OH)); 722 s (809) (ν (ReO)). The data in parenthesis is obtained by DFT calculations.

UV–Vis (H₂O, λ_max, nm (1 g ɛ)) 225 (3.2).

¹H NMR (DMSO d₆, δ ppm) OH (s, 4.7), H₂O (4.8).

Anal. Calc. for ReH₉O₁₄S₂ (1): Re, 38.5; S, 13.2; H, 1.8. Found: *Re, 36.8; *S, 12.9; H, 1.95%. * Were measured by gravimetric measurement.

2.3

2.3 Computational details

The Gaussian-98 suite of programs (Frisch et al., 2003) was used for the calculations. The geometry optimization of [Re(O)(OH)(H₂O)₄]²⁻ in a singlet state was carried out with the DFT method. The level of theory used to compute the structure was B3LYP/LANL2DZ (Lee et al., 1993). No negative frequency for the optimized structure was revealed from the analysis of hessian, which indicates that the structure was fully optimized. The calculated vibrational frequencies for [Re(O)(OH)(H₂O)₄]S₂O₈ in the infra red spectral range of 200–4000 cm⁻¹ are presented above, together with the experimentally recorded data. The results indicate that the used DFT method and basis set for [Re(O)(OH)(H₂O)₄]S₂O₈ are suitable for obtaining results with satisfactory agreement with the experiment. It should be mentioned that the theoretical values are usually higher than the experimental data. One has to scale the theoretical data by an optimal scaling factor. In our case a good agreement between the theoretical and experimental data was observed. Molecular drawings were obtained using the gausview98 software package.

3 Results and discussion

The [ReO(OH)(H₂O)₄]S₂O₈ complexes were prepared in good yields by direct reaction between metal salt NH₄ReO₄ and the ligand in the presence of a reducing agent. The complexation reactions were carried out according to the following equations: $S_{2} O_{8}^{2 -} + 2 {Re}^{5 +} + 6 H_{2} O \to S_{2} O_{6}^{2 -} + 2 {ReO}_{4}^{-} + 12 H^{+}$ $2 {SO}_{4}^{2 -} \to S_{2} O_{8}^{2 -} + 2 e^{-}$ The IR spectra [ReO(OH)(H₂O)₄]S₂O₈ displays a strong band assigned to ν (Re⚌O) at 996 cm⁻¹ which are in the range reported for similar mono-oxorhenium complexes (945–1067 cm⁻¹) Silverstein and Webstar, 1996 and the band due to ν (ReO) was recorded at 722 cm⁻¹. A sharp split band in the range 3238–3562 cm⁻¹ was observed and assigned to coordinated water in the structures of the complex (Nyquist and Kagel, 1971).

The electronic spectrum of the complex shows intensive absorption at 225 nm, attributed to intraligand transition, with a molar extinction coefficient of 3.2 M⁻¹ cm⁻¹, which is similar to the one reported earlier (Nakamoto, 1970).

¹H NMR spectra of complex (1) show a singlet at δ 4.77 ppm assigned to the OH, and another singlet at 4.8 ppm assigned to the coordinated water (Banwell, 1972).

3.1

3.1 Optimized geometry with DFT calculations

The geometry of [ReO(OH)(H₂O)₄]²⁻ was optimized in a singlet state by the DFT method with the B3LYP functional. The optimized geometric parameters are presented in Table 1. The calculated Re⚌O and Re–O bonds are in good agreement with the values reported for other oxo rhenium complexes of related structures (Machura et al., 2007a,b). It should be noted that Re–O bond of H₂O is relatively longer than the expected length found in other rhenium complexes. This indicates that rhenium is weakly bonded to H₂O groups and therefore is labile and may be replaced easily by other ligands.

Table 1 The optimized bond lengths (Å) and angles (°) for [ReO(OH)(H₂O)₄]²⁻.

Bond lengths	(Å)	Bond angles	(°)
R(1, 2)	1.702	A(2, 1, 5)	90.102
R(1, 3)	1.861	A(2, 1, 7)	91.091
R(1, 5)	2.155	A(2, 1, 9)	91.097
R(1, 7)	2.095	A(2, 1, 11)	90.187
R(1, 9)	2.095
R(1, 11)	2.155

The calculated charge on the rhenium atom in [ReO(OH)(H₂O)₄]S₂O₈ is considerably lower than the formal charge +5, corresponding to a d² configuration of the central ion. This results from charge donation of H₂O ligands. There is unequal occupancy of degenerate orbitals in this system – admittedly they are t_2g and so Jahn–Teller distortion effects will be more minor than in the case of unequal e_g occupancy. The terminal oxo ion is less negative in comparison with the oxygen atom of the hydroxy group in the trans position. It indicates higher electron density delocalization from the O_t ligand towards the central ion and corresponding to the differences in the Re–OH and Re⚌O bond lengths. Much less negative charge is reported for $O_{H_{2} O (5)}$ . Table 2 shows atomic charges for [ReO(OH)(H₂O)₄]²⁻. The charges for O9 and O11 are similar to O7 and O5, respectively.

Table 2 Showing atomic charges from the natural population analysis (NPA) for [ReO(OH)(H₂O)₄]².

Atom	Charge
Re(1)	1.6737
O(2)	−0.8527
O(3)	−0.9546
O(5)	−0.2154
O(7)	−0.9473

The structure of complex 1 [ReO(OH)(H₂O)₄]²⁻ as stabilized by DFT calculations is shown in Fig. 1.

Molecular structure of [ReO(OH)(H2O)4]2 obtained by DFT calculations.

3.2

3.2 Thermogravimetric analysis

Thermal decomposition behavior of the investigated complexes was followed using thermogravimetric (TG) and differential thermogravimetric (DTG) techniques. The complex under investigation has two decomposition steps.

The first decomposition step, in the range of 90–150 °C corresponding to the loss of four water molecules, was attributed to water of coordination. The second decomposition is in the range 200–500 °C. The thermal decomposition ends with the formation of the rhenium oxide Re₂O₇ at 900 °C Table 3. On the basis of the above observations, the following scheme for the thermal decomposition may be proposed. The thermogram is shown in Fig. 2. $ReO (OH) (H_{2} O)_{4}] S_{2} O_{8} \to_{90 – 150 ° C}^{4 H_{2} O (decoordination)} Intermediate (unstable)$ $Intermediate \to_{200 – 500 ° C}^{decomposition} Rhenium oxide ({Re}_{2} O_{7})$

Table 3 Thermal data of aqua oxorhenium complex.

Complex	Decomposition behavior		Percent decomp.		Assignment
	Steps	Temp. range (°C)	Calc%	Found%
[ReO(OH)(H₂O)₄]S₂O₈	First	90–150	14.9	15.3	Loss of 4H₂O
[ReO(OH)(H₂O)₄]S₂O₈	Second	200–500	30	31.5	Loss of violate

TG/DTA of complex 1 [ReO(OH)(H2O)4]S2O8 showing the weight loss steps.

3.3

3.3 Determination of reaction order of decomposition

The Horowitz and Metzger equation, C_s = (n)^1/1−ⁿ, where C_s is the weight fraction of the substance present at the DTG peak temperature, T_s is given as

(1)

C_{s} = (W_{s} - W_{f}) / (W_{i} - W_{f})

and, was used for the determination of the values of the reaction order (n). Here W_s stands for the remaining weight of the substance at a given temperature T_s, i.e., the DTG peak temperature, W_i and W_f are the initial and final weights of the substance, respectively. The values of C_s for the thermal decomposition of complexes are not in the range 0.30–0.39 which indicate that the decomposition is not first order kinetics (Horowitz and Metzger, 1963). For a first order process the Horowitz and Metzger equation may be written in the form:

(2)

\ln [\frac{1 - (1 - α)^{1 - n}}{1 - n}] = \ln \frac{{ART}_{S}^{2}}{ϕ Ea} - \frac{Ea}{RT} + \frac{Ea θ}{{RT}_{S}^{2}}

where R is the gas constant, Ea is the activation energy in J mol⁻¹, θ is the heating rate. The kinetic parameters were calculated from the plots of the left hand side of Eq. (2) and θ. The correlation coefficient r (>0.95) is computed using the least-square method for Eq. (2).

The activation entropy ΔS*, the activation enthalpy ΔH* and the free energy of activation ΔG* were calculated using the following equations (Abu-Eittah et al., 2006; Garcia et al., 1986):

(3)

Δ S^{*} = 2.303 R [\log \frac{Ah}{KT}]

(4)

Δ H^{*} = Ea - nRT

(5)

Δ G^{*} = Δ H^{*} - T_{S} Δ S^{*}

where K and h are the Boltzman and Plank constants, respectively. The calculated values of Ea, A, ΔS*, ΔH* and ΔG* for the two decomposition steps are given in Table 4.

Table 4 Kinetic and equilibrium parameters of the thermal decomposition of aqua oxorhenium complex.

Complex	Decomposition step (°C)	Ea (kJ mol⁻¹)	$Δ$ S* (JK⁻¹ mol⁻¹)	$Δ$ H* (kJ−mol⁻¹)	$Δ$ G* (kJ−mol⁻¹)	lnA (min⁻¹)
[ReO(OH)(H₂O)₄]S₂O₈	90–150	116	−165.3	96.5	156	1.4
[ReO(OH)(H₂O)₄]S₂O₈	200–500	359.4	−205.8	348.2	458	5.8

3.4

3.4 Applications of aqua rhenium oxocomplex

Use as a catalyst precursor for the catalytic oxidation of PPh₃ and cyclohexane.

Due to the weak nature of the Re–OH₂ bond, aqua complexes are very good starting materials in coordination chemistry. Reaction of (1) with excess PPh₃ in the presence of molecular oxygen was studied by in situ ³¹P{¹H} NMR spectroscopy. In the proposed mechanism the aqua rhenium oxocomplex (1) reacts with triphenylphosphine to form [Re(PPh₃)_n]³⁺ (2). The formation of complex (2) has been confirmed by spectroscopic studies. Complex (2) reacts with O₂ to form complex (3). The formation of complex [ReO(PPh₃)_n]³⁺ (3) and OPPh₃ has also been confirmed by spectroscopic studies. The oxygen atom transfer from complex (3) to PPh₃ may be a concerted process with the slow release of the product OPPh₃ as rate determining.

A ³¹P NMR spectrum of complex (3) shows three peaks initially at −18, −4 and 32 ppm, corresponding to PPh₃-complex, PPh₃-free and OPPh_3, respectively, as shown in Fig. 3.

31P{1H} NMR spectrum of complex 1 in the presence of excess PPh3.

The peak at −18 ppm is due to the Re complex formation with PPh₃. The peak at −4 ppm is due to excess free un-oxidised ligand and the peak at 32 ppm is due to the catalytic oxidation of PPh₃ with molecular oxygen resulting in the formation of OPPh₃. The downfield shift for the complex formation at −18 ppm clearly shows that there is more back donation of electrons from the metal Re to the ligand PPh₃ compared to the electron donation of PPh₃ to the metal in the complex formation.

Complex (1) was also used as a catalyst for the oxidation of cyclohexane with molecular oxygen as oxidant. The results as confirmed by gas chromatography indicate the formation of cylohexanol and cyclohexanone in trace amounts. Further studies are being made for the oxidation of cyclohexane using other oxidants.

According to our studies we can say that the complex (1) is a catalyst or precursor for preparing a new class of rhenium oxo complexes which can be used in catalytic oxidations.

4 Conclusions

The aqua complexe [ReO(OH)(H₂O)₄]S₂O₈ has been shown to be a good precursor for preparing a new class of rhenium oxo complexes which can be used in catalytic oxidations. In this respect, the [ReO(PPh₃)_n]³⁺ can be prepared by an exchange reaction between the aqua complex and free PPh₃. Either this complex or the aquo complex 1 can be used as a catalyst for the oxidation of PPh₃ to OPPh₃ using molecular oxygen as an oxidant.

Acknowledgments

We are thankful to the research Center, College of Science, King Saud University for a research Grant No. chem./2007/25 for this work. Thanks are also due to Mr. Abdulrahman Al-Harthi for technical assistance.

References

Abu-Eittah R.H., Zaki N.G., Mahamed M.M.A., Kamel L.T., . J. Anal. Appl. Pyrolysis. 2006;77:1.
Banwell C.N., . Fundamentals of Molecular Spectroscopy. New York: McGraw-Hill; 1972.
Blower P.J., Dilworth J.R., Hutchison J.P., Nicholson T., Zubieta J., . J. Chem. Soc. Dalton Trans. 1986:1339.
Chi D.Y., O’Neil J.P., Anderson C.J., Welch M.J., Katzenellenbogen J.A., . J. Med. Chem.. 1994;37:928.
Davison A., Jones A., . Int. J. Appl. Radiat. Isot.. 1982;33:875.
Deutsch E., Lipson K., Vanderheyden J.L., Ketring A.R., Maxon H.R., . Nucl. Med. Biol.. 1986;13:465.
Ehrhardt J., Ketring A.R., Turpin T.A., Razavi M.S., Vanderheyden J.L., Su F.M., Fritzberg A.R., . Nicolini M., Bandoli G., Mazzi U., eds. Technetium and Rhenium in Chemistry and Nuclear Medicine 3. Verona: Cortina International; 1990.
Frisch, M.J., Tucks, G.W., Schegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Montgomery Jr., J.A., Vreven, T., Kudin, K.N., Burant, J.C., Millam, J.M., Iyengar, S.S., Tomasi, J., Barone, V., Mennucci, B., Cossi, M., Scalmani, G., Rega, N., Petersson, G/A., Nakatsuji, H., Hada, M., Ehara, M., Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Klene, M., Li, X., Knox, J.E., Hratchian, H.P., Cross, J.B., Adamo, C., Jaramillo, J., Gomperts, R., Stratmann, R.E., Yazyev, O., Austin, A.J., Cammi, R., Pomelli, C., Ochterski, J.W., Ayala, P.Y., Morokuma, K., Voth, G.A., Salvador, P., Dannenberg, J.J., Zakrzewski, V.G., Dapprich, S., Daniels, A.D., Strain, M.C., Farkas, O., Malick, D.K., Rabuck, A.D., Raghavachari, K., Foresmann, J.B., Ortiz, J.V., Cui, Q., Baboul, A.G., Clifford, S., Cioslowski, J., Stefanov, B.B., Liu, G., Liashenko, A., Piskorz, P., Komaromi, I., Martin, R.L., Fox, D.J., Keith, T., Al-Laham, M.A., Peng, C.Y., Nanayakkara, A., Challacombe, M., Gill, P.M.W., Johnson, B., Chen, W., Wong, M.W., Gonzalez, C., Pople, J.A., 2003. GAUSSIAN 98 Revision B98. Gaussian Inc., Pittsburgh, PA.
Garcia J., Molla M.C., Borras J., Escriva E., . Thermochim. Acta. 1986;106:155.
Horowitz H.H., Metzger G., . Anal. Chem.. 1963;35:1464.
Jurisson S., Berning D., Jia W., Ma D., . Chem. Rev.. 1993;93:1137.
Lee C., Yang W., Parr R.G., . Phys. Rev. B. 1993;37:785.
Machura B., . Coord. Chem. Rev.. 2005;249:591.
Machura B., Kusz J., . Polyhedron. 2008;27:187.
Machura B., Kruszynski R., Mroziński J., . Polyhedron. 2007;26:1259.
Machura B., Kruszynski R., Kusz J., . Inorg. Chem. Commun.. 2007;10:494.
Nakamoto K., . Infrared Spectra of Inorganic and Coordination Compounds. New York: Wiley; 1970.
Nyquist R.A., Kagel R.O., . Infrared Spectra of Inorganic Compounds. New York: Academic Press; 1971.
Silverstein R.M., Webstar F.X., . Spectrometric Identification of Organic Compounds (sixth ed.). John Wiley and Sons Inc.; 1996.
Taqui Khan M.M., Siddiqui M.R.H., Amjad Hussain, Moiz M.A., . Inorg. Chem.. 1986;25:2765.

Introduction

Experimental

General procedure
Synthesis of [ReO(OH)(H2O)4]S2O8 (1)
Computational details

Results and discussion

Optimized geometry with DFT calculations
Thermogravimetric analysis
Determination of reaction order of decomposition
Applications of aqua rhenium oxocomplex

Conclusions

Fulltext Views
28

PDF downloads
2

View/Download PDF
Download Citations

BibTeX
RIS

Show Sections

[1] Abu-Eittah R.H., Zaki N.G., Mahamed M.M.A., Kamel L.T., . J. Anal. Appl. Pyrolysis. 2006;77:1.

[2] Banwell C.N., . Fundamentals of Molecular Spectroscopy. New York: McGraw-Hill; 1972.

[3] Blower P.J., Dilworth J.R., Hutchison J.P., Nicholson T., Zubieta J., . J. Chem. Soc. Dalton Trans. 1986:1339.

[4] Chi D.Y., O’Neil J.P., Anderson C.J., Welch M.J., Katzenellenbogen J.A., . J. Med. Chem.. 1994;37:928.

[5] Davison A., Jones A., . Int. J. Appl. Radiat. Isot.. 1982;33:875.

[6] Deutsch E., Lipson K., Vanderheyden J.L., Ketring A.R., Maxon H.R., . Nucl. Med. Biol.. 1986;13:465.

[7] Ehrhardt J., Ketring A.R., Turpin T.A., Razavi M.S., Vanderheyden J.L., Su F.M., Fritzberg A.R., . Nicolini M., Bandoli G., Mazzi U., eds. Technetium and Rhenium in Chemistry and Nuclear Medicine 3. Verona: Cortina International; 1990.

[8] Frisch, M.J., Tucks, G.W., Schegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Montgomery Jr., J.A., Vreven, T., Kudin, K.N., Burant, J.C., Millam, J.M., Iyengar, S.S., Tomasi, J., Barone, V., Mennucci, B., Cossi, M., Scalmani, G., Rega, N., Petersson, G/A., Nakatsuji, H., Hada, M., Ehara, M., Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Klene, M., Li, X., Knox, J.E., Hratchian, H.P., Cross, J.B., Adamo, C., Jaramillo, J., Gomperts, R., Stratmann, R.E., Yazyev, O., Austin, A.J., Cammi, R., Pomelli, C., Ochterski, J.W., Ayala, P.Y., Morokuma, K., Voth, G.A., Salvador, P., Dannenberg, J.J., Zakrzewski, V.G., Dapprich, S., Daniels, A.D., Strain, M.C., Farkas, O., Malick, D.K., Rabuck, A.D., Raghavachari, K., Foresmann, J.B., Ortiz, J.V., Cui, Q., Baboul, A.G., Clifford, S., Cioslowski, J., Stefanov, B.B., Liu, G., Liashenko, A., Piskorz, P., Komaromi, I., Martin, R.L., Fox, D.J., Keith, T., Al-Laham, M.A., Peng, C.Y., Nanayakkara, A., Challacombe, M., Gill, P.M.W., Johnson, B., Chen, W., Wong, M.W., Gonzalez, C., Pople, J.A., 2003. GAUSSIAN 98 Revision B98. Gaussian Inc., Pittsburgh, PA.

[9] Garcia J., Molla M.C., Borras J., Escriva E., . Thermochim. Acta. 1986;106:155.

[10] Horowitz H.H., Metzger G., . Anal. Chem.. 1963;35:1464.

[11] Jurisson S., Berning D., Jia W., Ma D., . Chem. Rev.. 1993;93:1137.

[12] Lee C., Yang W., Parr R.G., . Phys. Rev. B. 1993;37:785.

[13] Machura B., . Coord. Chem. Rev.. 2005;249:591.

[14] Machura B., Kusz J., . Polyhedron. 2008;27:187.

[15] Machura B., Kruszynski R., Mroziński J., . Polyhedron. 2007;26:1259.

[16] Machura B., Kruszynski R., Kusz J., . Inorg. Chem. Commun.. 2007;10:494.

[17] Nakamoto K., . Infrared Spectra of Inorganic and Coordination Compounds. New York: Wiley; 1970.

[18] Nyquist R.A., Kagel R.O., . Infrared Spectra of Inorganic Compounds. New York: Academic Press; 1971.

[19] Silverstein R.M., Webstar F.X., . Spectrometric Identification of Organic Compounds (sixth ed.). John Wiley and Sons Inc.; 1996.

[20] Taqui Khan M.M., Siddiqui M.R.H., Amjad Hussain, Moiz M.A., . Inorg. Chem.. 1986;25:2765.

New aqua rhenium oxocomplex; synthesis, characterization, thermal studies, DFT calculations and catalytic oxidations

Abstract

Keywords

Rhenium

Complexes

Catalysis

Oxidation

DFT calculations

1 Introduction

2 Experimental

2.1 General procedure

2.2 Synthesis of [ReO(OH)(H2O)4]S2O8 (1)

2.3 Computational details

3 Results and discussion

3.1 Optimized geometry with DFT calculations

3.2 Thermogravimetric analysis

3.3 Determination of reaction order of decomposition

3.4 Applications of aqua rhenium oxocomplex

4 Conclusions

Acknowledgments

References

Suggested read for related articles:

2.2 Synthesis of [ReO(OH)(H₂O)₄]S₂O₈ (1)