Tetra­kis[μ-N,N′-bis­(4-bromo­phen­yl)formamidinato-κ2 N:N′]dimolyb­denum(II) tetra­hydro­furan solvate

L-J Han

doi:10.1107/S1600536811011202

. 2011 Mar 31;67(Pt 4):m514. doi: 10.1107/S1600536811011202

Tetrakis[μ-N,N′-bis(4-bromophenyl)formamidinato-κ² N:N′]dimolybdenum(II) tetrahydrofuran solvate

L-J Han ^a,^*

PMCID: PMC3099865 PMID: 21754018

Abstract

The title complex, [Mo₂(C₁₃H₉N₂Br₂)₄]·C₄H₈O, contains a quadruply bonded Mo₂ ⁴⁺ unit equatorially coordinated by four N,N′-bis(4-bromophenyl)formamidinate ligands, forming a dimetal paddlewheel complex. The centroid of the Mo—Mo bond is located on a special position with 2/m symmetry. In the crystal, complex molecules are linked by Br⋯Br interactions [3.7049 (10) Å]. The disordered solvent molecule could not be satisfactorily modelled and was therefore eliminated from the final refinement.

Related literature

For the nature of halogen–halogen interactions, see: Domercq et al. (2001 ▶); Espallargas et al. (2006 ▶). For Br⋯Br interactions, see: Fujiwara et al. (2006 ▶); Reddy et al. (1996 ▶). For the use of intermolecular interactions in supramolecular synthesis, see: Brammer (2004 ▶); Desiraju (1995 ▶, 2001 ▶).

Experimental

Crystal data

[Mo₂(C₁₃H₉N₂Br₂)₄]·C₄H₈O
M _r = 1604.05
Monoclinic,
a = 21.795 (4) Å
b = 10.077 (2) Å
c = 29.967 (6) Å
β = 110.67 (3)°
V = 6158 (2) Å³
Z = 4
Mo Kα radiation
μ = 5.64 mm⁻¹
T = 293 K
0.15 × 0.13 × 0.10 mm

Data collection

BRUKER SMART 1000 diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ▶) T _min = 0.429, T _max = 0.569
25098 measured reflections
5995 independent reflections
3563 reflections with I > 2σ(I)
R _int = 0.119

Refinement

R[F ² > 2σ(F ²)] = 0.055
wR(F ²) = 0.151
S = 1.01
5995 reflections
317 parameters
H-atom parameters constrained
Δρ_max = 1.09 e Å⁻³
Δρ_min = −1.11 e Å⁻³

Data collection: APEX2 (Bruker, 2004 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811011202/ff2002sup1.cif

e-67-0m514-sup1.cif^{(20KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811011202/ff2002Isup2.hkl

e-67-0m514-Isup2.hkl^{(293.6KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Mo1—Mo1ⁱ	2.1263 (13)
Mo1—N3	2.192 (5)
Mo1—N4ⁱ	2.195 (5)
Mo1—N1ⁱ	2.198 (5)
Mo1—N2	2.218 (5)

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Symmetry code: (i) Inline graphic .

Acknowledgments

This work was supported by the National Natural Scientific Foundation of China (No.20741004/B010303).

supplementary crystallographic information

Comment

One of the main interests of crystal engineering is the study of intermolecular interactions and their utilization in supramolecular synthesis (Desiraju 1995; Desiraju 2001; Brammer 2004). These interactions range from strong forces, e.g., classical hydrogen bonds, to weaker ones, e.g., halogen···halogen interactions. The nature of the halogen···halogen interactions has been studied both through extensive crystallographic investigation and using ab initio calculations(Domercq et al.,2001; Espallargas et al., 2006). Here we report intermolecular Br···Br interactions in the crystal structure Mo₂(C₁₃H₉N₂Br₂)₄.THF.

The molecular structure of the title compound is shown in Fig.1. The molecule of Mo₂(C₁₃H₉N₂Br₂)₄ (I) occupies a special position on an inversion center, and the Mo—Mo distance is 2.1263 (13) Å, which is in the range of dimolybdenum quadruple bonds. Bromine atoms participate in short contacts (3.7049 (10) Å) linking the molecules of (I) into planes. This value is significantly shorter than van der Waals contact distance (3.90 Å) (Reddy et al., 1996; Fujiwara et al., 2006).

Experimental

A mixture yellow Mo₂(OOCCH₃)₄ (0.128 g, 0.300 mmol) and N,N'-bis(4-bromophenyl)formamidinate (0.425 g, 1.20 mmol) was suspended in 20 ml of THF. While stirring, 2.4 ml NaOCH₂CH₃ solution (0.5 M in ethanol) was added slowly. The colour turned first to red and then to dark red. The reaction was stirred for 5 h at room temperature, and then the volume of the solvent was reduced to about 3 ml under reduced pressure. The residue was washed with distilled water(3×10 ml) and ethanol (8 ml) and dried under vacuum. The yellow solid was dissolved in THF (15 ml) and the solution was layered with hexanes. Yellow block-shaped crystals formed after several days. Yield: 0.342 g (71%). ¹HNMR(CDCl₃, p.p.m.): 8.41(s, 4H, –NCHN–), 7.10(d, 16H, aromatic), 6.06(d, 16H, aromatic). Anal. Calcd. C₅₂H₃₆Mo₂N₈Br₈: C, 38.94; H, 2.26; N, 6.99; Found: C, 38.78; H, 2.17; N, 7.08.