Limits...
Crystal structure of cyclo-tris-(μ-3,4,5,6-tetra-fluoro-o-phenyl-ene-κ(2) C (1):C (2))trimercury-tetra-cyano-ethyl-ene (1/1).

Castañeda R, Timofeeva TV, Khrustalev VN - Acta Crystallogr E Crystallogr Commun (2015)

Bottom Line: The donor-acceptor Hg⋯N inter-actions do not affect the C N bond lengths [1.136 (6) and 1.140 (6) Å].The remaining N atoms of two nitrile groups of B are not engaged in any donor-acceptor inter-actions.In the crystal, the mixed stacks are held together by inter-molecular C-F⋯C N secondary inter-actions [2.846 (5)-2.925 (5) Å].

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry & Biology, New Mexico Highlands University, 803 University Ave., Las Vegas, NM 87701, USA.

ABSTRACT
The title compound, [Hg3(C6F4)3]·C6N4, contains one mol-ecule of tetra-cyano-ethyl-ene B per one mol-ecule of mercury macrocycle A, i.e., A•B, and crystallizes in the monoclinic space group C2/c. Macrocycle A and mol-ecule B both occupy special positions on a twofold rotation axis and the inversion centre, respectively. The supra-molecular unit [A•B] is built by the simultaneous coordination of one of the nitrile N atoms of B to the three mercury atoms of the macrocycle A. The Hg⋯N distances range from 2.990 (4) to 3.030 (4) Å and are very close to those observed in the related adducts of the macrocycle A with other nitrile derivatives. The mol-ecule of B is almost perpendicular to the mean plane of the macrocycle A at the dihedral angle of 88.20 (5)°. The donor-acceptor Hg⋯N inter-actions do not affect the C N bond lengths [1.136 (6) and 1.140 (6) Å]. The trans nitrile group of B coordinates to another macrocycle A, forming an infinite mixed-stack [A•B]∞ architecture toward [101]. The remaining N atoms of two nitrile groups of B are not engaged in any donor-acceptor inter-actions. In the crystal, the mixed stacks are held together by inter-molecular C-F⋯C N secondary inter-actions [2.846 (5)-2.925 (5) Å].

No MeSH data available.


Related in: MedlinePlus

TGA diagram of free B (in red) and complex (I) (in blue).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4644994&req=5

fig5: TGA diagram of free B (in red) and complex (I) (in blue).

Mentions: Despite complexes (I) and (II) being structural analogs, they are substanti­ally different in their chemical stability. The crystalline complex (II) decomposes over a few days, while complex (I) is stable in the solid state for several months under ambient conditions. As free B decomposes rapidly upon reaction with moisture to produce toxic hydrogen cyanide, the high chemical stability of complex (I) is surprising. Moreover, the thermal stability of complex (I) has been studied by thermogravimetric analysis (TGA) which revealed that, upon complexation, tetra­cyano­ethyl­ene is stable to higher temperatures (Fig. 5 ▸). So, the free compound B starts to decompose at 363 K, but, being incorporated into the supra­molecular complex (I), B is stable up to 393 K. Complex (I) decomposes in two different steps. The first step of a 18.3% weight loss is attributed to molecule B because the much lower decomposition temperature of this molecule compared to macrocycle A. Consequently, the second weight loss of 81.7% is attributed to decomposition of macrocycle A. The complete decomposition of the free B is complete at 445 K; however, its final decomposition temperature is equal to 467 K within the supra­molecular complex (I). Final decomposition of complex (I) occurs at 573 K, and is likely due decomposition of macrocycle A.


Crystal structure of cyclo-tris-(μ-3,4,5,6-tetra-fluoro-o-phenyl-ene-κ(2) C (1):C (2))trimercury-tetra-cyano-ethyl-ene (1/1).

Castañeda R, Timofeeva TV, Khrustalev VN - Acta Crystallogr E Crystallogr Commun (2015)

TGA diagram of free B (in red) and complex (I) (in blue).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644994&req=5

fig5: TGA diagram of free B (in red) and complex (I) (in blue).
Mentions: Despite complexes (I) and (II) being structural analogs, they are substanti­ally different in their chemical stability. The crystalline complex (II) decomposes over a few days, while complex (I) is stable in the solid state for several months under ambient conditions. As free B decomposes rapidly upon reaction with moisture to produce toxic hydrogen cyanide, the high chemical stability of complex (I) is surprising. Moreover, the thermal stability of complex (I) has been studied by thermogravimetric analysis (TGA) which revealed that, upon complexation, tetra­cyano­ethyl­ene is stable to higher temperatures (Fig. 5 ▸). So, the free compound B starts to decompose at 363 K, but, being incorporated into the supra­molecular complex (I), B is stable up to 393 K. Complex (I) decomposes in two different steps. The first step of a 18.3% weight loss is attributed to molecule B because the much lower decomposition temperature of this molecule compared to macrocycle A. Consequently, the second weight loss of 81.7% is attributed to decomposition of macrocycle A. The complete decomposition of the free B is complete at 445 K; however, its final decomposition temperature is equal to 467 K within the supra­molecular complex (I). Final decomposition of complex (I) occurs at 573 K, and is likely due decomposition of macrocycle A.

Bottom Line: The donor-acceptor Hg⋯N inter-actions do not affect the C N bond lengths [1.136 (6) and 1.140 (6) Å].The remaining N atoms of two nitrile groups of B are not engaged in any donor-acceptor inter-actions.In the crystal, the mixed stacks are held together by inter-molecular C-F⋯C N secondary inter-actions [2.846 (5)-2.925 (5) Å].

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry & Biology, New Mexico Highlands University, 803 University Ave., Las Vegas, NM 87701, USA.

ABSTRACT
The title compound, [Hg3(C6F4)3]·C6N4, contains one mol-ecule of tetra-cyano-ethyl-ene B per one mol-ecule of mercury macrocycle A, i.e., A•B, and crystallizes in the monoclinic space group C2/c. Macrocycle A and mol-ecule B both occupy special positions on a twofold rotation axis and the inversion centre, respectively. The supra-molecular unit [A•B] is built by the simultaneous coordination of one of the nitrile N atoms of B to the three mercury atoms of the macrocycle A. The Hg⋯N distances range from 2.990 (4) to 3.030 (4) Å and are very close to those observed in the related adducts of the macrocycle A with other nitrile derivatives. The mol-ecule of B is almost perpendicular to the mean plane of the macrocycle A at the dihedral angle of 88.20 (5)°. The donor-acceptor Hg⋯N inter-actions do not affect the C N bond lengths [1.136 (6) and 1.140 (6) Å]. The trans nitrile group of B coordinates to another macrocycle A, forming an infinite mixed-stack [A•B]∞ architecture toward [101]. The remaining N atoms of two nitrile groups of B are not engaged in any donor-acceptor inter-actions. In the crystal, the mixed stacks are held together by inter-molecular C-F⋯C N secondary inter-actions [2.846 (5)-2.925 (5) Å].

No MeSH data available.


Related in: MedlinePlus