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Synthesis and X-ray diffraction data of dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl) molybdenum (VI)

Published online by Cambridge University Press:  20 February 2023

Jose L. Pinto ,
Hernando Camargo  and
Nelson J. Castellanos Open the ORCID record for Nelson J. Castellanos [Opens in a new window]
Jose L. Pinto
Affiliation:
Grupo de Investigación de Materiales de Interés Geológico y Geotécnico, Dirección de Laboratorios, Servicio Geológico Colombiano SGC, Diagonal 53 No. 34-53, Bogotá́, Colombia
Hernando Camargo
Affiliation:
Grupo de Investigación de Materiales de Interés Geológico y Geotécnico, Dirección de Laboratorios, Servicio Geológico Colombiano SGC, Diagonal 53 No. 34-53, Bogotá́, Colombia
Nelson J. Castellanos*
Affiliation:
Laboratorio de Diseño y Reactividad de Estructuras Sólidas (Lab-DRES, 125), Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Carrera 30 No. 45-03, Bogotá́ 111321, Colombia
*
a)Author to whom correspondence should be addressed. Electronic mail: njcastellanosm@unal.edu.co
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Abstract

The dichloro-dioxide-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex was prepared from molybdenum(VI)-dichloride-dioxide and 4,4′-dimethyl-2,2′-bipyridyl in CH2Cl2 obtaining a clear green solution. The molybdenum complex was precipitated using ethyl ether, separated by filtration and the light green solid washed with ethyl ether. The XRPD pattern for the new compound showed that the crystalline compound belongs to the monoclinic space group P21/n (No.14) with refined unit-cell parameters a = 12.0225(8) Å, b = 10.3812(9) Å, c = 11.7823(9) Å, β = 103.180(9)°, unit-cell volume V = 1431.79 Å3, and Z = 4.

Keywords

dioxomolybdenum (VI) complexX-ray powder diffractionbiomimetic compounds
Type
New Diffraction Data
Information
Powder Diffraction , Volume 38 , Issue 2 , June 2023 , pp. 152 - 157
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Copyright
Copyright © The Author(s), 2023. Published by Cambridge University Press on behalf of International Centre for Diffraction Data

I. INTRODUCTION

Molybdenum is an essential element in all forms of life (Schoepp-Cothenet et al., Reference Schoepp-Cothenet, Van Lis, Philippot, Magalon, Russell and Nitschke2012; Kapp, Reference Kapp2014), and is mainly associated with enzymes that catalyze the oxidative process of a wide range of aldehydes and aromatic heterocycles, and oxygen atom transfer processes (OAT) in nature using the molecular oxygen (O2) as an oxidizing agent (Hille et al., Reference Hille, Nishino and Bittner2011; Castellanos, Reference Castellanos2014). These natural systems, known as molybdenum-enzymes, are the source of inspiration to synthesize different complexes called “biomimetics” that have allowed an advance in the understanding of the molecular oxygen activation mechanisms (Dupé et al., Reference Dupé, Judmaier, Belaj, Zangger and Mösch-Zanetti2015; Heinze, Reference Heinze2015). Adapting these natural systems into analogous bio-inspired complexes, several structures of MoVIO2 with a variety of ligands have been synthesized and evaluated in OAT processes for substrates such as alkanes, alkenes, and phosphines (Bakhtchadjian et al., Reference Bakhtchadjian, Tsarukyan, Barrault, Martinez, Tavadyan and Castellanos2011; Kück et al., Reference Kück, Reich and Kühn2016). Recently, the photocatalytic activity of some dioxo-molybdenum complexes supported on different supports as metal-organic framework (MOF) or inorganic oxides as TiO2 or SiO2 were assessed in the selective epoxidation of terpenes as α- and β-pinene or limonene, using molecular O2 as the primary oxidizing agent (Castellanos et al., Reference Castellanos, Martínez, Páez-Mozo, Ziarelli and Arzoumanian2012, Reference Castellanos, Martínez, Lynen, Biswas, Van Der Voort and Arzoumanian2013; Martínez et al., Reference Martínez, Amaya, Páez-Mozo and Martínez2018, Reference Martínez, Amaya, Paez-Mozo, Martinez and Valange2020, Reference Martínez, Paez-Mozo and Martínez2021). In all cases, the epoxide was formed as the sole product and intermediate peroxo-molybdenum species were identified in the reoxidation process using infrared and EPR spectroscopy (Castellanos et al., Reference Castellanos, Martínez, Martínez, Leus and Van Der Voort2021; Martínez et al., Reference Martínez, Valezi, Di Mauro, Páez-Mozo and Martínez2022). In this work, we report the synthesis, molecular characterization (FTIR, NMR), and X-ray powder diffraction data of the dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex as a biomimetic active center of molybdenum-enzymes.

II. EXPERIMENTAL

All chemicals, including 4,4′-dimethyl-2,2′-bipyridine and MoO2Cl2 were purchased from Sigma-Aldrich and used without further purification. Commercial grade solvents were dried and deoxygenated by refluxing for at least 12 h over appropriate drying agents under argon atmosphere and were freshly distilled prior to use. IR (KBr) were recorded with a Perkin-Elmer 1720XFT and 1H and 13C NMR were performed with Bruker Avance 400 spectrometer. The CHN elemental analysis was performed on a Thermo Scientific Flash 2000 CHNS/O analyzer equipped with a TCD detector. Molybdenum elemental analysis was carried out with an atomic absorption spectrophotometer Thermo S4. The samples were analyzed after acid digestion with previous calcination in a muffle furnace at 500 °C for 5 h.

A. Synthesis of dichloro-dioxo-(4,4′-dimethyl-2,2′-bipyridine)-molybdenum (VI)

A solution of dichloromethane (10 ml) containing 0.200 g (1.0 mmol) of MoO2Cl2 was slowly added to 0.184 g (1.0 mmol) of the 4,4′-dimethyl-2,2′-bipyridine ligand dissolved in dichloromethane (15 ml) under a nitrogen atmosphere (Figure 1). The reaction was stirred for 12 h at room temperature protected from light. The reaction mixture was mixed with 15 ml of ethyl ether and the resulting solid was filtered and washed three times with 20 ml of ethyl ether to obtain a light green solid. (0.220 g; %R = 57.2) IR (cm−1) KBr: 3074 (=CH), 2988 (CH), 1616 (C=C), 1423 (C=C), 935 (Mo = Oasym), 907 (Mo = Osym). 1H NMR (400 MHz, CDCl3) δ 9.43 (d, J = 5.5 Hz, 2H), 8.05 (s, 2H), 7.53 (d, J = 7.8 Hz, 2H), 2.62 (s, 6H). Elemental analysis calculated for C12H12Cl2MoN2O2 (383.1): C 37.62, H 3.16, N 7.31. Found: C 37.81, H 2.98, N 6.98. Molybdenum elemental calculated: 25.1%, obtained: 27.0%.

Figure 1. Synthesis of dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex.

B. Data collection

X-ray powder diffraction (XRPD) of the dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex was carried out at 298 K using an X'Pert Pro MPD PANalytical equipment with Cu anode (CuKα radiation, λ = 1.5418 Å) and Bragg–Brentano geometry using a nickel filter and with a high-speed solid-state detector for data acquisition PIXcel. A receiving slit (RS) of 0.6 mm and primary and secondary soller slits (SS) of 2.5° were used. The diffraction data were collected over the range from 5.00 to −80.00° 2θ with a step size of 0.0263° 2θ and counting time of 97.920 s with a No. of points of 2856.

III. RESULTS AND DISCUSSION

The synthesis and single-crystal structure of the dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex were initially reported at room temperature using molybdenum acetate as precursor and collected X-ray data at 173 K (Baird et al., Reference Baird, Yang, Kavanaugh, Finness and Dunbar1996) obtaining a monoclinic unit cell with a = 11.7556 (2), b = 10.369 (62), c = 11.956 (2) Å, α = 90°, β = 103.57 (2)°, γ = 90°, V = 1415.5 (5) Å3, and a space group P21/n (No.14). In this study, reaction at room temperature (298 K) using MoO2Cl2 as molybdenum source, yields the title compound which was confirmed by their elemental and spectroscopic analysis. The powder diffraction pattern (Figure 2) was indexed on a monoclinic unit cell with least squares fit lattice parameters a = 11.9914 (4), b = 10.3662 (4), c = 11.7556 (4) Å, β = 103.126 (3)°, V = 1423.11 Å3 using DICVOL04 program (Boultif and Louër, Reference Boultif and Louër2004) and PreDICT graphical interface (Blanton et al., Reference Blanton, Papoular and Louër2019) with figures of merit: M(20) = 16.8 and F(20) = 40.0 (0.0132, 38). Analysis of the systematic absences using EXPO2013 (Altomare et al., Reference Altomare, Cuocci, Giacovazzo, Moliterni, Rizzi, Corriero and Falcicchio2013) suggested the space group P21/n (No. 14) (Table I). The refinement was performed with TOPAS v.6 (Pawley, Reference Pawley1981) fitting using the whole powder pattern decomposition (WPPD) procedure. A Chebyshev Polynomial was used to fit the background (Figure 2). The final Pawley fit yielded the unit-cell parameters a = 12.0225(8) Å, b = 10.3812(9) Å, c = 11.7823(9) Å, β = 103.180(9)°, unit-cell volume V = 1431.79 Å3, and Z = 4 (Table II). The lack of impurity lines and good residual values from Pawley fit (R exp, R wp, R p, and GoF) obtained from the refinement process allowed to conclude that the sample corresponds to a single-phase and high-quality experimental data was obtained. The volumetric thermal expansion coefficient (α = 5.78 × 10−5 K−1) has been determined using the unit-cell volume obtained in this study at 298 K and the value reported per single crystal at 100 K, using the following relation: ln(V/Vo) = α(T–To) (Megaw, Reference Megaw1971; Ishige et al., Reference Ishige, Masuda, Kozaki, Fujiwara, Okada and Ando2017; van der Lee and Dumitrescu, Reference van der Lee and Dumitrescu2021).

Figure 2. X-ray powder diffraction pattern of the title compound using CuKα radiation (blue solid line) and the refined pattern of the compound (red solid line).

TABLE I. X-ray powder diffraction data for dichloro-dioxide-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex.

The d-values were calculated using CuKα 1 radiation (λ = 1.5405981 Å).

TABLE II. Experimental data for dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex using powder and single crystal analysis.

ACKNOWLEDGEMENTS

This work was financially supported by the Universidad Nacional de Colombia and the Facultad de Ciencias de la Universidad Nacional de Colombia by the internal Projects code Hermes 52711. N.J.C. appreciates the collaboration of the Professor Luis Carlos Moreno from the X-Ray Powder Diffraction laboratory of Universidad Nacional de Colombia.

CONFLICTS OF INTEREST

The authors have no conflicts of interest to declare.

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Figure 0

Figure 1. Synthesis of dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex.

Figure 1

Figure 2. X-ray powder diffraction pattern of the title compound using CuKα radiation (blue solid line) and the refined pattern of the compound (red solid line).

Figure 2

TABLE I. X-ray powder diffraction data for dichloro-dioxide-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex.

Figure 3

TABLE II. Experimental data for dichloro-dioxido-(4,4′-dimethyl-2,2′-bipyridyl)-molybdenum (VI) complex using powder and single crystal analysis.