Syntheses and Characterization of (Diamine-N,N‘-dicarboxylato)chromate(III) Dinuclear Complexes Bridged by Pyrazole-3,5-dicarboxylate:  X-ray Structures of Na[Cr₂(edda)₂(μ-pzdc)]·5H₂O and Na[Cr₂(trdda)₂(μ-pzdc)]·3H₂O

Abstract

New pyrazole-3,5-dicarboxylato (pzdc) chromate(III) complexes containing linear tetradentate edda (ethylenediamine-N,N′-diacetate), trdda (trimethylenediamine-N,N′-diacetate), or eddp (ethylenediamine-N,N′-dipropionate) were synthesized and characterized by elemental analyses, column chromatography, 2 H NMR, FAB mass spectra, and X-ray analyses. Crystallographic data for Na[Cr 2 (edda) 2 (µ-pzdc)]·5H 2 O (1) are monoclinic with space group P2 1 /n, a ) 11.73(1) Å, b ) 19.475(6) Å, c ) 13.229(6) Å, ) 111.99(5)°, Z ) 4, and a final R factor of 0.056 based on 4673 reflections. Na[Cr 2 (trdda) 2 (µ-pzdc)]·3H 2 O (2) crystallizes in the orthorhombic space group Fdd2, with a ) 16.576(4) Å, b ) 29.235(6) Å, c ) 12.544(5) Å, Z ) 8, and a final R factor of 0.078 based on 2456 reflections. In both complexes two Cr(III) units were bridged by a pzdc. The complex 1 and 2 has a (symcis)-(unsym-cis) edda and (unsym-cis)-(unsym-cis) trdda geometrical configuration, respectively. Unlike the edda and trdda ligands, the eddp ligand formed mononuclear pzdc complexes, which may correspond to two geometrical isomers of unsym-cis-mer-and fac-[Cr(eddp)(pzdc)] 2- (3 and 4). The differences in the formations of the pzdc Cr(III) complexes with the edda-type ligands were demonstrated to arise from the chelate ring sizes and/or the intramolecular interaction such as hydrogen bond and van der Waals contact between two Cr(III)-edda type units. The hydrogen bond between the edda moieties following stereognostic coordination brings about the novel inert unsym-cis configuration in complex 1.

Crystal structure and conformational analysis of s-cis-(acetylacetonato)(ethylenediamine-N,N′-diacetato)-chromium(III)

“…Therefore, as in all previous cases [11], MM succeeded in correlating the most stable structure of an edtatype complex with the one found experimentally by X-ray diffraction. For stereochemically relatively simple [Cr(edda)-(acac)] species this result was hardly surprising: the previous MM calculations on systems containing an edda ligand [1], as well as all reported crystal structures [44,[46][47][48][49] (except one, discussed below), confirm the general tendency for the quadridentate edda ligand to adopt preferentially the s-cis geometry in coordination to Cr(III). Moreover, there is a remarkable similarity of the edda backbone conformation among all the crystal structures containing a Cr(edda) fragment [44,46] and our [Cr(edda)(acac)] structure, as illustrated in Fig.…”

“…The stereochemisty of octahedral complexes containing quadridentate edda 2− ligand has been described by Legg et al [6], and reiterated by many subsequent authors, notably by Kaizaki et al [44,45]. However, CFF modelling requires (particularly in elucidating statistical thermodynamics) a consideration of all theoretically possible configurations and conformations, which represent local minima on the potential energy surface of [Cr(edda)(acac)].…”

Absolute Chiral Structures of Inorganic Compounds

“…171 [ T 2 magnetic dipole-allowed transition region. Thus, these diastereomers assume a D absolute configuration according to the major CD component rule.…”

“…Of the possible two sym-cis and unsym-cis geometrical isomers for Cr(III) complexes containing tetradentate linear ligands with only five-membered chelate rings ( Figure 5.40), the cdda ligand prefers a sym-cis configuration over an unsym-cis one in view of the preparative process of the pzdc-bridged dinuclear [Cr 2 (m-pzdc) (edda or cdda) 2 ] À complexes (pzdc 3À ¼ pyrazorate-3,5-dicarboxylate; edda ¼ ethylenediamine-N,N 0 -diacetate). 171,172 If the absolute configuration around chromium(III) ion is L, the R,R-cdda takes a sym-cis configuration with an axial orientation (normal) of two glycinates (NC ax ), as depicted in Figure 5.41. On the other hand, the D-sym-cis configuration results from stereoselective coordination of the equatorially oriented glycinates (abnormal NC eq ) ( Figure 5.41).…”

Self-assembly of supermolecular species directed by hydrogen bonding and aromatic π-π stacking interactions

“…These multifunctional coordination sites are highly accessible to metal ions; H 3 pdc can coordinate as a mono-, bi-, or tetradentate ligand and can act to link together to the metal centers through a number of bridging modes. A variety of its coordination compounds containing transition, lanthanide and alkalineearth metals have been synthesized and reported in the literature [26][27][28][29][30]. Second, it can act both as an excellent hydrogen donor and hydrogen acceptor in hydrogen bonding, which interactions are fundamental in supramolecular chemistry.…”