Crystal and molecular structure of tris(glycinato)chromium(III) monohydrate, Cr(C2H4NO2)3.H2O

Abstract

Figure 4.-The coordination polyhedron about the Pr(II1) ion showing the monocapped square-antiprismatic configuration.is bent down toward plane B as can be seen in Figure 3. Since this complex contains constraints of chelating as well as three different kinds of atoms in the coordination sphere, it does not lend itself to detailed analysis of the coordination polyhedron. Day and Hoard2; have noted that the quasi-Cd axis [N(1)-Pr] corresponding to the Cdv symmetry of the idealized monocapped square antiprism must generate four axes [Pr-N(l), Pr-N(2), Pr-N(2)', and Pr-Cl(1)] normal to which are observed one-five-three layering of the ligated atoms. Examination of the model does show such layering.A reasonable pattern of three-dimensional hydrogen bonding (Table 111) can be proposed as O(1) + Cl(1)"' and O(5) O ( 2 ) + Cl(2) and O(4) O ( 3 ) + Cl(2) and C1(l)vr O(4) + C1(2)11 and C1(2)Ir1 O(5) + C1(2)Iv and C1(2)v This scheme thus links each complex ion to all six of its neighboring ions via hydrogen bonding. This threedimensional hydrogen bonding is manifested in the excellent crystals corresponding to the octahydrated complex. The crystal and molecular structure of tris( glycinato)chrornium( 111) monohydrate, Cr( C S H~N O~)~ HzO, has been determined by single-crystal X-ray analysis. The cell constants are a = 6.256 ( l ) , b = 14.649 (l), c = 12.267 (1) A, and fl = 100.39 (1)'.The space group is P&/c and with 2 = 4 the calculated density is 1.755 g/cin3 compared to the observed 1.76 (1) g/c1n3. Scintillation counter diffractonietry was used to measure the intensities of 2631 independent reflections significantly above background. The phase problem was solved by the application of direct methods and the structural parameters refined by a block-diagonal least-squares procedure to a final R of 0.0266. All hydrogen atoms in the structure were located and their positional parameters were refined. Anisotropic thermal parameters were used for all atoms except hydrogen. The chromium ion is octahedrally coordinated by three glycinato ligands so that the three nitrogen atoms are mutually cis.

Kinetic studies on chromium-glycinato complexes in acidic and alkaline media

“…On the other hand, it is likely that a higher bioavailability characterizes chromium(III) complexes with amino acids, as naturally existing biomolecules. However, though many chromium-amino acids complexes are known [11][12][13][14][15][16], to date no studies on their kinetics in aqueous solutions or their cytotoxicity were performed. In this work, studies on chromium-glycinato complexes are described.…”

“…In this work, studies on chromium-glycinato complexes are described. Two compounds, [Cr(gly) 3 ] and [Cr(gly) 2 (OH)] 2 , were obtained earlier [11][12][13] and their structures were determined by X-ray diffraction. The tris-complex was found to be the fac-isomer [12].…”

“…Two compounds, [Cr(gly) 3 ] and [Cr(gly) 2 (OH)] 2 , were obtained earlier [11][12][13] and their structures were determined by X-ray diffraction. The tris-complex was found to be the fac-isomer [12]. In the dimer [15], the chromium atoms, connected by two hydroxo bridges, have two gly coordinated in cis positions such that introduction of the third gly yields the fac-isomer.…”

“…In the dimer [15], the chromium atoms, connected by two hydroxo bridges, have two gly coordinated in cis positions such that introduction of the third gly yields the fac-isomer. The complexes were practically insoluble in aqueous solutions at pH 7, and therefore only spectroscopic characteristics for Nujol mulls were done [12,16]. Some preliminary studies on their acidcatalysed aquation [16] demonstrated that they form the same, exceptionally inert (in acidic media) product of [Cr(gly) 2 …”

Thermodynamical detection of hydrophobic hydration of tris(2,4-pentanedionato)-cobalt(III) and tris(3,5-heptanedionato)cobalt(III) in water

“…It has been found that the crystal of f~c -C r ( g l y )~. H~O has a threedimensional network of intermolecular hydrogen bonds between the chelate molecules, and that the water molecule in the crystal also serves to link two molecules of the chelate (18). These facts suggest that the dissolution of f a c -C~( g l y )~ in W results from hydrophilic hydration composed of the hydrogen bond between the carboxylic andlor amino groups of the chelate and water molecules.…”