μ-Acetato-aqua-μ-(5-bromo-2-{1,3-bis­[2-(5-bromo-2-oxidobenzyl­idene­amino)­eth­yl]imidazolidin-2-yl}phenolato)methano­ldinickel(II) methanol disolvate monohydrate

Ahmed Raza Khan; Yohannes Tesema; Ray J Butcher; Yilma Gultneh

doi:10.1107/S1600536811035409

. 2011 Sep 14;67(Pt 10):m1381–m1382. doi: 10.1107/S1600536811035409

μ-Acetato-aqua-μ-(5-bromo-2-{1,3-bis[2-(5-bromo-2-oxidobenzylideneamino)ethyl]imidazolidin-2-yl}phenolato)methanoldinickel(II) methanol disolvate monohydrate

Ahmed Raza Khan ^a, Yohannes Tesema ^a, Ray J Butcher ^a,^*, Yilma Gultneh ^a

PMCID: PMC3201549 PMID: 22058698

Abstract

The crystal structure of the title compound, [Ni₂(C₂₇H₂₄Br₃N₄O₃)(CH₃CO₂)(CH₃OH)(H₂O)]·2CH₃OH·H₂O contains [L(OAc){(CH₃OH)Ni}{(H₂O)Ni}] molecules {H₃ L = 2-(5-bromo-2-hydroxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine} with additional water and two methanol solvent molecules. In this instance, one of the two Ni atoms is coordinated to a water and the other to a methanol molecule. The Ni—O and Ni—N distances, as well as the angles about the metal atoms, show quite regular octahedra around the central ions. The Ni—O_phenol—Ni and Ni—O_acetate—Ni angles are not similar [95.26 (13) and 97.34 (13)°, respectively], indicating that this subtle solvate exchange induces significant differences in the conformation adopted. The coordinated methanol ligand is involved in an intramolecular hydrogen bond to the uncoordinated O atom of the bridging acetate ligand, while the coordinated water molecule forms a hydrogen bond with the one of the methanol solvent molecules. The water solvent molecule forms strong hydrogen bonds to both phenolate O atoms. The remaining methanol solvent molecule also forms a hydrogen bond with this solvent water molecule.

Related literature

For nickel complexes of similar ligands, see: Fondo et al. (2005 ▶, 2006a ▶,b ▶, 2007 ▶, 2009 ▶); Khan et al. (2011 ▶); Lu et al. (2007 ▶); Paital et al. (2007 ▶, 2009 ▶).

Experimental

Crystal data

[Ni₂(C₂₇H₂₄Br₃N₄O₃)(C₂H₃O₂)(CH₄O)(H₂O)]·2CH₄O·H₂O
M _r = 1000.85
Orthorhombic,
a = 14.7385 (16) Å
b = 18.552 (2) Å
c = 14.2504 (15) Å
V = 3896.4 (7) Å³
Z = 4
Mo Kα radiation
μ = 4.10 mm⁻¹
T = 168 K
0.49 × 0.12 × 0.06 mm

Data collection

Bruker SMART 1000 CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2000 ▶) T _min = 0.676, T _max = 1.000
25239 measured reflections
8737 independent reflections
6627 reflections with I > 2σ(I)
R _int = 0.054

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.092
S = 0.96
8737 reflections
479 parameters
7 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.71 e Å⁻³
Δρ_min = −0.73 e Å⁻³
Absolute structure: Flack (1983 ▶), 3686 Friedel pairs
Flack parameter: 0.007 (8)

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2000 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811035409/wm2523sup1.cif

e-67-m1381-sup1.cif^{(37.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811035409/wm2523Isup2.hkl

e-67-m1381-Isup2.hkl^{(427.4KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1W—H1W1⋯O2Wⁱ	0.80 (2)	2.01 (2)	2.810 (5)	174 (5)
O1W—H1W2⋯O3M	0.82 (2)	1.97 (3)	2.770 (5)	164 (5)
O2W—H2W1⋯O1B	0.80 (2)	1.86 (3)	2.631 (5)	160 (6)
O2W—H2W2⋯O1A	0.83 (2)	1.91 (2)	2.744 (5)	177 (6)
O1M—H1M⋯O2AA	0.84	1.77	2.602 (5)	174
O2M—H2M⋯O2W	0.84	1.89	2.725 (5)	172
O3M—H3M⋯O2Mⁱ	0.84	1.96	2.753 (6)	158

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Symmetry code: (i) Inline graphic .

Acknowledgments

RJB wishes to acknowledge the NSF–MRI program (grant CHE-0619278) for funds to purchase the diffractometer. ARK and YT wish to acknowledge the Howard University Graduate School of Arts & Sciences for the award of Teaching Assistanceships.

supplementary crystallographic information

Comment

Nickel complexes of the compartmental triprotic heptadentate ligand, 2-hydroxyphenyl-1,3-bis[4-(2-hydroxyphenyl)-3-azabut- 3-enyl]-1,3-imidazolidine and its derivatives have been of interest for their ability to give rise to dinuclear compounds with a predefined ground state (Fondo et al., 2005, 2006a,b, 2007, 2009; Lu et al., 2007; Paital, et al., 2007, 2009). Density functional theory (DFT) calculations demonstrated that the Schiff base provides an NCN bridge between the metal ions that helps to mediate the ferromagnetic exchange (Fondo, et al., 2005). Consequently, the use of suitable cross-linking ligands between the dinuclear units could be a route to produce complexes of higher nuclearity, with all of the unpaired electrons aligned parallel to each other. The type of complex obtained depends on the synthesis conditions as the coordination environment about the metals is usually completed by coordinating solvent molecules.

The crystal structure shows that the title compound, [Ni₂(CH₃CO₂)(C₂₇H₂₄Br₃N₄O₃) (H₂O)(CH₃OH)]^.2CH₃OH^.H₂O, (I), contains [L(OAc){(CH₃OH)Ni}{(H₂O)Ni}] molecules (H₃L = 2-(5-bromo-2-hydroxyphenyl)-1,3-bis[4-(5-bromo-2- hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) with water and two methanol molecules as solvates. In this instance one of the two nickel atoms is coordinated to a water and the other to a methanol molecule. This is in contrast to its related complex involving the ligand 2-(5-chloro-2-hydroxyphenyl)-1,3-bis[4-(5-chloro-2-hydroxyphenyl)-3-azabut-3- enyl]-1,3-imidazolidine, which was synthesized under similar conditions. In this case both nickel atoms contain coordinated methanol molecules (Khan et al., 2011). It has previous been observed that nickel complexes involving this type of ligand are prone to solvate exchange (Fondo et al., 2009).

(I) is a neutral dinuclear compound, where the L^3- Schiff base acts as a trianionic heptadentate ligand, using each one of its N₂O compartments to coordinate a nickel atom. Thus, the metal atoms are joined to one terminal phenol oxygen (O1A, O1B), an iminic nitrogen (N1A, N1B), and an aminic nitrogen atom (N1, N2), with the aminic NCN group (N2—C7—N2) acting as a bridge between both nickel ions. In addition, the nickel atoms are linked by the endogenous phenolate oxygen atom (O1) of the central ligand arm and by an exogenous bridging monodentate acetate group (O11A). This gives rise to a nearly planar Ni₂O₂ metallacycle, with an intramolecular Ni—Ni distance of 3.0927 (9) Å. The coordination spheres of the nickel atoms are completed by solvent molecules. In the case of Ni1A by water and in the case of Ni1B by methanol molecules. Therefore, the metal atoms are hexacoordinated in a N₂O₄ environment, with an octahedral geometry. The Ni—O and Ni—N distances, as well as the angles about the metal atoms, show quite regular polyhedra around the central ions. However, unlike the analogous complex formed with 2-(5-chloro-2-hydroxyphenyl)-1,3-bis[4-(5-chloro-2- hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine (Khan et al., 2011) the Ni—O_phenol—Ni and Ni—O_acetate—Ni angles are not similar [95.26 (13)° and 97.34 (13)°, respectively] and more closely related to a similar complex (Fondo et al., 2009) with a similar coordination environment about the two Ni atoms (one with water and the other with methanol coordinated). Thus this subtle solvate exchange induces significant differences in the conformation adopted. There are structures of Ni complexes involving similar ligands reported in the literature which differ only in the nature of the coordinating solvent (H₂O) and solvate molecules (H₂O, CH₃CN) in the lattice (Fondo et al., 2006b) and similar differences are observed.

The coordinated methanol ligand is involved in an intramolecular hydrogen bond to the uncoordinated O atom (O2AA) of the bridging acetate ligand while the coordinated water molecule forms a hydrogen bond with the one of the methanol solvate molecules. The solvate water molecule forms strong hydrogen bonds to both O1A and O1B. The remaining methanol solvate molecule also forms a hydrogen bond with this water solvate molecule.

Experimental

For the synthesis of the ligand (H₃L) methanol solutions of triethylenetetramine and 5-bromosalicylaldehyde were mixed in a 1:3 molar ratio. After heating at 333 K for a few minutes, diethylether was added to this mixture, and yellow crystals were separated, filtered and recrystallized from methanol solution: Mp 376 K. For synthesis of the complex, to a stirred methanol solution (25 ml) of [Ni(OAc)₂]^.4H₂O (1.5 g, 2.67 mmol) was added 1.33 g (5.35 mmol) of the ligand H₃L. Slow evaporation of the green filtrate overnight yielded green to brownish cystal suitable for X-ray analysis in 70% yield.