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Crystal structure of di-chlorido-(4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-deca-ne)iron(III) hexa-fluorido-phosphate.

Funwie NL, Cain AN, Fanning BZ, Hageman SA, Mullens M, Roberts TK, Turner DJ, Valdez CN, Vaughan RW, Ermias HG, Silversides JD, Archibald SJ, Hubin TJ, Prior TJ - Acta Crystallogr E Crystallogr Commun (2015)

Bottom Line: Inter-molecular C-H⋯Cl inter-actions exist in the structure between the complex ions.Comparison with the mononuclear Fe(2+) complex of the same ligand shows that the smaller Fe(3+) ion is more fully engulfed by the cavity of the bicyclic ligand.Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-decane prevent dimerization upon oxidation.

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Affiliation: Department of Chemistry and Physics, Southwestern Oklahoma State University, Weatherford, OK 73096, USA.

ABSTRACT
The title compound, [FeCl2(C14H30N4)]PF6, contains Fe(3+) coordinated by the four nitro-gen atoms of an ethyl-ene cross-bridged cyclam macrocycle and two cis chloride ligands in a distorted octa-hedral environment. In contrast to other similar compounds this is a monomer. Inter-molecular C-H⋯Cl inter-actions exist in the structure between the complex ions. Comparison with the mononuclear Fe(2+) complex of the same ligand shows that the smaller Fe(3+) ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-decane prevent dimerization upon oxidation.

No MeSH data available.


Mol­ecular structure of μ-oxidobis[chlorido­(1,4,8,11-tetra­aza­bicyclo[6.6.2]hexa­deca­ne)iron(III)] (Hubin et al., 2003 ▸).
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fig3: Mol­ecular structure of μ-oxidobis[chlorido­(1,4,8,11-tetra­aza­bicyclo[6.6.2]hexa­deca­ne)iron(III)] (Hubin et al., 2003 ▸).

Mentions: From a comparison of the Fe3+ 4,11-dimethyl-1,4,8,11-tetra­aza­bicyclo­[6.6.2]hexa­adecane dichloride complex hexa­fluorido­phosphate with the Fe2+ analogue, the reduction in ionic radius of the iron ion upon oxidation is clear (Table 1 ▸). Nax—Fe3+—Nax is 166.8 (3)° in the present structure, while Nax—Fe2+—Nax is 161.88 (5)° in the reduced complex (Hubin et al., 2000 ▸). The smaller Fe3+ ion is pulled further into the ligand cavity as the favored octa­hedral geometry is approached, as can be seen by viewing each complex down the Nax—Fen+—Nax axis (Fig. 2 ▸). Fe—N bond lengths are also affected, going from a mean of 2.255 Å in the Fe2+ complex, to 2.209 Å in the Fe3+ complex. Comparison of the present Fe3+ monomer with the μ-oxido dimer complex is also informative. The crystal structure of the dimeric Fe3+ complex (Hubin, 2003 ▸) is represented in Fig. 3 ▸. The Fe3+ ion of this complex is also found in a pseudo-octa­hedral, six-coordinate geometry. Usually, these dimers contain five-coordinate metal cations, although dimers with six- and seven-coordinate cations are known (Murray, 1974 ▸). However, one monodentate chlorido ligand is maintained in this structure. Since the macrocyclic ligand is uncharged, the attractive Coulombic forces between the halide and the Fe3+ ion may be enough to keep it bound. Also, the folded ligand conformation helps separate the ligands from each other, easing the steric inter­actions that might favor lower coordination numbers with more nearly planar ligands. The secondary amine/Fe3+ bond lengths in the dimer are somewhat shorter than the tertiary amine/Fe3+ bond lengths: the Fe—N(secondary) mean length is 2.153 Å while the Fe—N(tertiary) mean length is 2.239 Å. In the monomer, with all tertiary amines, the mean Fe—N bond length is 2.209 Å, shorter but not quite matching that of the shortest, secondary amine bonds in the dimer. The Nax—Fe—Nax mean bond angle is 161.6° in the dimer, while this value is 166.85 (19)° in the monomer. Clearly, dimerization, and its associated steric consequences, pulls the Fe3+ ion further out of the ligand cavity than it is in the Fe3+ monomer. In fact, the dimer Nax—Fe—Nax bond angle is much closer to that of the Fe2+ monomer at 161.88 (5)° than that of the Fe3+ monomer at 166.85 (19)°. This steric consequence is consistent with the observation that the more sterically demanding methyl-substituted ligand prevents dimerization altogether.


Crystal structure of di-chlorido-(4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-deca-ne)iron(III) hexa-fluorido-phosphate.

Funwie NL, Cain AN, Fanning BZ, Hageman SA, Mullens M, Roberts TK, Turner DJ, Valdez CN, Vaughan RW, Ermias HG, Silversides JD, Archibald SJ, Hubin TJ, Prior TJ - Acta Crystallogr E Crystallogr Commun (2015)

Mol­ecular structure of μ-oxidobis[chlorido­(1,4,8,11-tetra­aza­bicyclo[6.6.2]hexa­deca­ne)iron(III)] (Hubin et al., 2003 ▸).
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fig3: Mol­ecular structure of μ-oxidobis[chlorido­(1,4,8,11-tetra­aza­bicyclo[6.6.2]hexa­deca­ne)iron(III)] (Hubin et al., 2003 ▸).
Mentions: From a comparison of the Fe3+ 4,11-dimethyl-1,4,8,11-tetra­aza­bicyclo­[6.6.2]hexa­adecane dichloride complex hexa­fluorido­phosphate with the Fe2+ analogue, the reduction in ionic radius of the iron ion upon oxidation is clear (Table 1 ▸). Nax—Fe3+—Nax is 166.8 (3)° in the present structure, while Nax—Fe2+—Nax is 161.88 (5)° in the reduced complex (Hubin et al., 2000 ▸). The smaller Fe3+ ion is pulled further into the ligand cavity as the favored octa­hedral geometry is approached, as can be seen by viewing each complex down the Nax—Fen+—Nax axis (Fig. 2 ▸). Fe—N bond lengths are also affected, going from a mean of 2.255 Å in the Fe2+ complex, to 2.209 Å in the Fe3+ complex. Comparison of the present Fe3+ monomer with the μ-oxido dimer complex is also informative. The crystal structure of the dimeric Fe3+ complex (Hubin, 2003 ▸) is represented in Fig. 3 ▸. The Fe3+ ion of this complex is also found in a pseudo-octa­hedral, six-coordinate geometry. Usually, these dimers contain five-coordinate metal cations, although dimers with six- and seven-coordinate cations are known (Murray, 1974 ▸). However, one monodentate chlorido ligand is maintained in this structure. Since the macrocyclic ligand is uncharged, the attractive Coulombic forces between the halide and the Fe3+ ion may be enough to keep it bound. Also, the folded ligand conformation helps separate the ligands from each other, easing the steric inter­actions that might favor lower coordination numbers with more nearly planar ligands. The secondary amine/Fe3+ bond lengths in the dimer are somewhat shorter than the tertiary amine/Fe3+ bond lengths: the Fe—N(secondary) mean length is 2.153 Å while the Fe—N(tertiary) mean length is 2.239 Å. In the monomer, with all tertiary amines, the mean Fe—N bond length is 2.209 Å, shorter but not quite matching that of the shortest, secondary amine bonds in the dimer. The Nax—Fe—Nax mean bond angle is 161.6° in the dimer, while this value is 166.85 (19)° in the monomer. Clearly, dimerization, and its associated steric consequences, pulls the Fe3+ ion further out of the ligand cavity than it is in the Fe3+ monomer. In fact, the dimer Nax—Fe—Nax bond angle is much closer to that of the Fe2+ monomer at 161.88 (5)° than that of the Fe3+ monomer at 166.85 (19)°. This steric consequence is consistent with the observation that the more sterically demanding methyl-substituted ligand prevents dimerization altogether.

Bottom Line: Inter-molecular C-H⋯Cl inter-actions exist in the structure between the complex ions.Comparison with the mononuclear Fe(2+) complex of the same ligand shows that the smaller Fe(3+) ion is more fully engulfed by the cavity of the bicyclic ligand.Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-decane prevent dimerization upon oxidation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry and Physics, Southwestern Oklahoma State University, Weatherford, OK 73096, USA.

ABSTRACT
The title compound, [FeCl2(C14H30N4)]PF6, contains Fe(3+) coordinated by the four nitro-gen atoms of an ethyl-ene cross-bridged cyclam macrocycle and two cis chloride ligands in a distorted octa-hedral environment. In contrast to other similar compounds this is a monomer. Inter-molecular C-H⋯Cl inter-actions exist in the structure between the complex ions. Comparison with the mononuclear Fe(2+) complex of the same ligand shows that the smaller Fe(3+) ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-decane prevent dimerization upon oxidation.

No MeSH data available.