Conformational diversity of dichromate dianion (original) (raw)
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Acta crystallographica. Section E, Crystallographic communications, 2017
The structure of the complex salt, cis-[Cr(NCS)2(cyclam)]2[Cr2O7]·H2O (cyclam = 1,4,8,11-tetra-aza-cyclo-tetra-decane, C10H24N4), has been determined from synchrotron data. The asymmetric unit comprises of one [Cr(NCS)2(cyclam)](+) cation, one half of a Cr2O7(2-) anion (completed by inversion symmetry) and one half of a water mol-ecule (completed by twofold rotation symmetry). The Cr(III) ion is coordinated by the four cyclam N atoms and by two N atoms of cis-arranged thio-cyanate anions, displaying a distorted octa-hedral coordination sphere. The Cr-N(cyclam) bond lengths are in the range 2.080 (2) to 2.097 (2) Å while the average Cr-N(NCS) bond length is 1.985 (4) Å. The macrocyclic cyclam moiety adopts the cis-V conformation. The bridging O atom of the dichromate anion is disordered around an inversion centre, leading to a bending of the Cr-O-Cr bridging angle [157.7 (3)°]; the anion has a staggered conformation. The crystal structure is stabilized by inter-molecular hydrogen bon...
Acta crystallographica. Section E, Crystallographic communications, 2016
The structure of the title compound, [CrCl2(tn)2]2[Cr2O7] (tn = propane-1,3-di-amine; C3H10N2), has been determined from synchrotron data. The asymmetric unit contains one Cr(III) complex cation and half a [Cr2O7](2-) anion. In the complex cation, the Cr(III) ion is coordinated by the four N atoms of two propane-1,3-di-amine (tn) ligands in the equatorial plane and by two Cl atoms in a trans configuration, displaying a distorted octa-hedral coordination sphere. The two six-membered rings in the complex cation have an anti chair-chair conformation with respect to each other. The mean Cr-N(tn) and Cr-Cl bond lengths are 2.09 (1) and 2.320 (2) Å, respectively. The slightly bent dichromate anion is disordered over two sets of sites (occupancy ratio = 0.7:0.3) and has a staggered conformation. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the NH2 groups of the tn ligands as donors and the O atoms of the [Cr2O7](2-) anion and chlorido ligands as acceptors.
Acta crystallographica. Section E, Crystallographic communications, 2017
The asymmetric unit of the title compound, [Cr(C2O4)(C10H24N4)]2[Cr2O7]·8H2O (C10H24N4 = 1,4,8,11-tetra-aza-cyclo-tetra-decane, cyclam; C2O4 = oxalate, ox) contains one [Cr(ox)(cyclam)](+) cation, one half of a dichromate anion that lies about an inversion centre so that the bridging O atom is equally disordered over two positions, and four water mol-ecules. The terminal O atoms of the dichromate anion are also disordered over two positions with a refined occupancy ratio 0.586 (6):0.414 (6). The Cr(III) ion is coordinated by the four N atoms of the cyclam ligand and one bidentate oxalato ligand in a cis arrangement, resulting in a distorted octa-hedral geometry. The Cr-N(cyclam) bond lengths are in the range 2.069 (2)-2.086 (2) Å, while the average Cr-O(ox) bond length is 1.936 Å. The macrocyclic cyclam moiety adopts the cis-V conformation. The dichromate anion has a staggered conformation. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the cyclam N-...
On the Analysis of the Cr−Cr Multiple Bond in Several Classes of Dichromium Compounds
Inorganic Chemistry, 2010
Since the discovery of a formal quintuple bond in Ar 0 CrCrAr 0 (CrCr = 1.835 Å ) by Power and co-workers in 2005, many efforts have been dedicated to isolating dichromium species featuring quintuple-bond character. In the present study we investigate the electronic configuration of several, recently synthesized dichromium species with ligands using nitrogen to coordinate the metal centers. The bimetallic bond distances of Power's compound and Cr 2 -diazadiene (1) (CrCr = 1.803 Å ) are compared to those found for Cr 2 (μ-η 2 -ArNC(R)NAr) 2 (2) (CrCr = 1.746 Å ; R = H, Ar = 2,6-Et 2 C 6 H 3 ), Cr 2 (μ-η 2 -Ar Xyl NC(H)NAr Xyl ) 3 (3) (CrCr = 1.740 reduced /1.817 neutral Å ; Ar Xyl = 2,6-C 6 H 3 -(CH 3 ) 2 ), Cr 2 (μ-η 2 -TippPyNMes) 2 (4) (CrCr = 1.749 Å ; TippPyNMes = 6-(2,4,6-triisopropylphenyl)pyridin-2-yl (2,4,6-trimethylphenyl)amide), and Cr 2 (μ-η 2 -DippNC(NMe 2 )N-Dipp) 2 (5) (CrCr = 1.729 Å , Dipp = 2,6-i-Pr 2 C 6 H 3 ). We show that the correlation between the CrCr bond length and the effective bond order (EBO) is strongly affected by the nature of the ligand, as well as by the steric hindrance due to the ligand structure (e.g., the nature of the coordinating nitrogen). A linear correlation between the EBO and CrCr bond distance is established within the same group of ligands. As a result, the CrCr species based on the amidinate, aminopyridinate, and guanidinate ligands have bond patterns similar to the Ar 0 CrCrAr 0 compound. Unlike these latter species, the dichromium diazadiene complex is characterized by a different bonding pattern involving Cr-Nπ interactions, resulting in a lower bond order associated with the short metal-metal bond distance. In this case the short CrCr distance is most probably the result of the constraints imposed by the diazadiene ligand, implying a Cr 2 N 4 core with a closer CrCr interaction.
Dihydronium tetrachromate(VI), (H3O)2Cr4O13
Acta Crystallographica Section E Structure Reports Online, 2013
The crystal structure of (H3O)2Cr4O13is isotypic with K2Cr4O13. The finite tetrachromate anion in the title structure consists of four vertex-sharing CrO4tetrahedra and exhibits a typical zigzag arrangement. The crystal packing is stabilized by hydrogen bonds between these anions and hydronium cations. The two different hydronium cations are surrounded by nine O atoms of tetrachromate anions, with O...O distances ranging between 2.866 (8) and 3.282 (7) Å.
Inorganic Chemistry, 1979
The title compounds, Cr2[PhNC(O)CH3I4, 1, and Mo2[PhNC(O)CH3I4, 2, the first tetraamidodimetal compounds with quadruple MM bonds, are described. They are prepared by reaction of the M2(02CCH3)4 compounds with Li[PhNC(O)CH,]. 1 was obtained as the unsolvated compound and the structure determined by X-ray crystallography. The crystals belong to space group Zd with a = 12.739 (6) A, c = 9.251 (3) A, and Z = 2. Each molecule has a(&) crystallographic symmetry and the Cr-Cr distance is 1.873 (4) A. The molybdenum compound, 2, was also obtained in unsolvated form but crystals large enough for X-ray work could not be obtained. The bis(tetrahydr0furanate) Mo2[PhNC(0)CH,].2THF did give suitable crystals, in space group P2,/c with a = 9.849 (2) A, b = 11.622 (2) A, c = 17.957 (2) A, /3 = 95.32 (1) O , and Z = 2, in which each molecule resides on a crystallographic inversion center and has an Mo-Mo distance of 2.086 (2) A. The ligand arrangement is different from that in 1; the MoN202 groups have a cis configuration and the overall symmetry of the M o~(N C O)~ grouping is C2h. This is the first time homologous Cr;+ and M024+ complexes have been found to differ structurally in a qualitative way.
Acta crystallographica. Section E, Crystallographic communications, 2017
The asymmetric unit of the hydrated title salt, (C10H28N4)[Cr2O7]2·H2O [C10H28N4 = H4(cyclam) = 1,4,8,11-tetra-azonia-cyclo-tetra-deca-ne], contains two half-cations (both completed by crystallographic inversion symmetry), two dichromate anions and one water mol-ecule. The two [CrO7](2-) anions exhibit a nearly staggered conformation, with bridging angles of 133.37 (11) and 136.28 (12)°. The distortions of the dichromate anions are due to their participation in hydrogen-bonding inter-actions with the water mol-ecule and the cations. Inter-molecular hydrogen bonds involving the cyclam N-H groups and water O-H groups as donor groups, and the O atoms of the dichromate anions as acceptor groups give rise to a three-dimensional network.
Acta crystallographica. Section E, Crystallographic communications, 2016
The structure of the title hybrid compound, (C6H16N2)[CrO4], has been determined from synchrotron data. The organic cation adopts a chair conformation. The inorganic CrO4(2-) anion is slightly distorted owing to its involvement in N-H⋯O hydrogen-bonding inter-actions with neighbouring trans-cyclo-hexane-1,2-di-ammonium cations, whereby the two Cr-O bonds to the O atoms acting as acceptor atoms for two hydrogen bonds are slightly longer than the other two Cr-O bonds for which only one acceptor inter-action per O atom is observed. In the crystal, cations and anions are packed into layers parallel to (001), held together through the aforementioned N-H⋯O hydrogen bonds.