A new MoVI Schiff base complex: methanol[N′-(3-meth­oxy-2-oxidobenzyl­idene)benzohydrazidato]dioxido­molybdenum(VI)

Iran Sheikhshoaie; Vratislav Langer; Seyed Ali Yasrebi

doi:10.1107/S1600536811020101

. 2011 Jun 4;67(Pt 7):m839–m840. doi: 10.1107/S1600536811020101

A new Mo^VI Schiff base complex: methanol[N′-(3-methoxy-2-oxidobenzylidene)benzohydrazidato]dioxidomolybdenum(VI)

Iran Sheikhshoaie ^a,^*, Vratislav Langer ^b, Seyed Ali Yasrebi ^a

PMCID: PMC3152014 PMID: 21836845

Abstract

In the title benzilidene Schiff base molybdenum(VI) complex, [Mo(C₁₅H₁₂N₂O₃)O₂(CH₃OH)], the Mo^VI ion is coordinated by two oxide O atoms and by two O atoms and one N atom of the tridentate N′-(3-methoxy-2-oxidobenzylidene)benzohydrazidate (L) Schiff base ligand. The methanol O atom completes the distorted octahedral configuration of the Mo^VI atom. Strong O—H⋯N hydrogen bonds form a C(5) chain around a 2₁ screw axis. Weak C—H—O hydrogen bonds are also present.

Related literature

For general background, see: Alizadeh et al. (1999 ▶); Ambroziak et al. (2004 ▶); Archer & Wang (1990 ▶); Bagherzadeh & Amini (2009 ▶); Bagherzadeh et al. (2008 ▶); Bhatia et al. (1981 ▶); Bindlish et al. (1978 ▶); Blake et al. (1995 ▶); Chang et al. (1998 ▶); Costamagna et al. (1992 ▶); Dhar & Taploo (1982 ▶); Hatefi et al. (2009 ▶); Holm (1990 ▶); Jalali-Heravi et al. (1999 ▶); Johnson et al. (1996 ▶); Maurya et al. (1997 ▶); Sheikhshoaie & Fabian (2009 ▶); Yamada (1999 ▶). For details of the synthesis, see: Perrin et al. (1990 ▶). For related structures, see: Dinda et al. (2006 ▶); Glowiak et al. (2003 ▶); Liimatainen et al. (2000 ▶); Monadi et al. (2009 ▶); Niaz et al. (2010 ▶); Pramaniky et al. (2007 ▶); Rao et al. (1999 ▶); Rezaeifard et al. (2010 ▶); Saeednia et al. (2009 ▶); Sheikhshoaie et al. (2009 ▶); Vrdoljak et al. (2010 ▶).

Experimental

Crystal data

[Mo(C₁₅H₁₂N₂O₃)O₂(CH₄O)]
M _r = 428.25
Monoclinic,
a = 29.400 (13) Å
b = 8.553 (4) Å
c = 14.391 (6) Å
β = 112.993 (8)°
V = 3331 (2) Å³
Z = 8
Mo Kα radiation
μ = 0.82 mm⁻¹
T = 173 K
0.58 × 0.54 × 0.46 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.368, T _max = 0.703
27788 measured reflections
5867 independent reflections
4401 reflections with I > 2σ(I)
R _int = 0.065

Refinement

R[F ² > 2σ(F ²)] = 0.038
wR(F ²) = 0.104
S = 1.01
5867 reflections
229 parameters
H-atom parameters constrained
Δρ_max = 1.38 e Å⁻³
Δρ_min = −1.80 e Å⁻³

Data collection: SMART (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2003 ▶); data reduction: SAINT and SADABS (Sheldrick, 2003 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2010 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶) and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811020101/dn2692sup1.cif

e-67-0m839-sup1.cif^{(25.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811020101/dn2692Isup2.hkl

e-67-0m839-Isup2.hkl^{(287.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected geometric parameters (Å, °).

Mo1—O1	2.0281 (19)
Mo1—O2	1.9391 (17)
Mo1—O4	1.7096 (18)
Mo1—O5	1.7093 (19)
Mo1—N1	2.248 (2)
Mo1—O1M	2.3374 (18)

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Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1M—H1M⋯N2ⁱ	0.84	1.87	2.700 (3)	173
C1M—H1BM⋯O1ⁱⁱ	0.98	2.58	3.402 (3)	141
C6—H6⋯O4ⁱⁱⁱ	0.95	2.53	3.450 (3)	162
C11—H11⋯O1	0.95	2.44	2.767 (3)	100
C15—H15⋯O1Mⁱⁱ	0.95	2.54	3.427 (3)	156

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

This work was supported by the Shahid Bahonar University of Kerman.

supplementary crystallographic information

Comment

The condensation products of primary amines and aldehydes or ketones (RCH=NR'), where R and R' represent alkyl and /or aryl constituents), are called Schiff bases (Dhar & Taploo, 1982); they play an important role in inorganic chemistry (Blake et al., 1995; Johnson et al.,1996; Alizadeh et al., 1999) as they easily form stable complexes with most transition metal ions. Transition metal compounds containing the Schiff base ligands have been of interest for many years (Yamada, 1999; Chang et al., 1998; Archer & Wang, 1990; Sheikhshoaie & Fabian, 2009; Jalali-Heravi et al., 1999). Many complexes play an important role in the developing of coordination chemistry related to catalytic (Holm, 1990; Rao et al., 1999; Bagherzadeh et al., 2008; Ambroziak et al., 2004; Bagherzadeh & Amini, 2009; Hatefi et al., 2009) and enzymatic reactions (Bindlish et al., 1978; Bhatia et al., 1981; Costamagna et al., 1992). High valent metal oxo species have demonstrated the ability to catalyze the oxidation of a variety of organic substrates, via homogeneous as well as heterogeneous routes (Holm, 1990; Maurya et al., 1997). In particular, the Mo-catalyzed alkene to epoxide conversion has received most attention. In the course of our studies on transition metal Schiff base complexes (Sheikhshoaie et al., 2009; Monadi et al., 2009), we have synthesized a dioxo molybdenium complex with a tridentate ligand (L) and the crystal structure of the title complex (I) is presented here.

The molecular structure of (I) is shown in Fig. 1. and the selected bond distances and angles are given in Table 1. The calculated bond valence by PLATON (version 91110: Spek, 2009) for Mo atom is 5.89, i.e. it exhibits the oxidation state +VI. Mo atom is surrounded by two O atoms and one N atom of the tridentate Schiff base ligand 3-methoxysalicylidenbenzoyl hydrazine in a distorted octahedral configuration. The Mo—O distances of the oxo ligands (O4 and O5) are significantly shorter [average 1.7094 (18) Å] than the corresponding distances to the O atoms of the tridentate ligands (O1 and O2) [average 1.98 (6) Å]. The Mo—N distance is longer [2.248 (2) Å] and the distance to methanol O atom is longest.

The aromatic ring C1/C2/C3/C4/C5/C6 is slightly distorted (χ² = 56.6), while the phenyl ring C10/C11/C12/C13/C14/C15 is planar (χ² = 4.7); the dihedral angle between them is 23.09 (12)^o.

There are strong hydrogen bonds present between the hydroxy group of methanol and N2ⁱ atom in an adjacent complex [symmetry code: (i):-x + 1/2,y + 1/2,-z + 1/2] forming thus a C(5) chain around 2₁ screw axis, see Fig.2. There are also weak hydrogen bonds of the type in the C—H—O hydrogen bonds present, see Table 2. Fig. 3 shows the packing of the complexes in the unit cell, but there are no π-π interactions present.

Comparison with other similar structures is presented in Table 3. In all complexes molybdenum atom is coordinated by two oxo oxygen atoms, one nitrogen atom of C=N group and one oxygen atom from solvent (methanol or ethanol). In all these complexes, the longest bond from the solvent coordination indicates the most labile site available for substitution. In addition, in all the investigated complexes the bonds between molybdenium atom and nitrogen atom of imine group (C=N) are long (average: 2.26 (2) Å). Two oxo oxygen atoms are almost in cis position towards each other in all the cases [the average of the O=Mo=O angles: 106.1 (5)°]. The angles of N—Mo=O in the complexes indicate that one of the oxo oxygen atoms is in cis and the other one is in trans position toward nitrogen atom of imine group. The coordination geometry around Mo atoms is highly distorted octahedral in [MoO₂(L) (solvent)] complexes, where (L) is a tridentate ligand containing an imine group and MeOH or EtOH as a solvent. Table 4 provides a comparison of important frequencies in the IR spectra of (I) and some dioxo-molybdenum(VI) complexes.

Experimental

All reagents were used assupplied by Fluka and Merck without further purification. Solvents used for the reaction were purified and dried by conventional methods (Perrin et al., 1990).

NMR spectra were obtained on a BRUKER AVANCE DRX500 (500 MHz) spectrometer. Proton chemical shifts δ are reported in p.p.m. relative to an internal standard of Me₄Si. Elemental analyses were performed by using Heraeus CHN-O-RAPID elemental analyzer. IR spectra were recorded in KBr pellets using Shimadzu 435 spectrophotometer.

Synthesis of ligand (L): To a solution of 0.136 g(0.001 mol) benzohydrazide in 20 ml e thanol was added a solution of 0.152 g(0.001 mol) 3-methoxysalicylaldehyde in 10 ml e thanol, and refluxed for 5 h. The solvent was evaporated on a rotatory evaporator and the solid dissolved in 10 ml me thanol and filtered off. The filtrate was left overnight to give yellow crystals. Yield: 202 mg (75%). Anal. Calc. for C₁₅H₁₄N₂O₃: C, 66.66; H, 5.18; N, 10.37. Found: C, 66.79; H, 5.20; N, 10.39%. IR (KBr, cm^-1) ν_max 1652.9 (s, C=O), 1614 (m, C=N). ¹H NMR: (d₆-DMSO): δ 3.81 (s, 3H, methoxy group), δ 6.84–7.96 (m, 8H, ArH), δ 8.671 (s, 1H, –CH=N– group), δ 11.02 (s, 1H, OH group), δ 12.09 (s, 1H, NH group).

Synthesis of the title metal complex (I) [Mo O₂(L)(CH₃OH)]: The title dioxomolybdenum(VI) complex was prepared by mixing MoO₂(acac)₂ (acac=.acetylacetonate) with the ligand in a 1:1 molar ratio using 30 ml dry methanol as a solvent, followed by refluxing the solution for 4 h. Deeply orange crystals were collected by filtration and dried in the room temperature, yield: 83%. ¹H NMR: δ 3.80 (s, 3H, metoxy group), δ 7.006–8.01 (m, 8 H, Ar H), δ 8.92 (s, 1H, –CH=N– group), δ 4.08–4.11 (s, 1H, OH methanol group); δ 3.16 (d, 3H CH₃ in methanol). IR spectra are presented in Table 4 [frequencies ν(N—H) and ν(C=O) were not observed].