Cyanoaquochromium(III) Complexes: Isolation, Spectra, Aquation Reactions and Kinetics

Schaap, Ward B.; Krishnamurthy, R.; Wakefield, Diane K.; Coleman, William F.

doi:10.1007/978-1-4899-6555-4_12

Cited by 8 publications

(6 citation statements)

References 11 publications

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“…K 3 [Cr(CN) 6 ] was synthesized by a slight modification to the reported procedure . For en·2HCl, a solution of 10 mL of ethylenediamine ( d = 0.899 g/mL, 150 mmol) in 30 mL of H 2 O was added to 30 mL of 37% HCl ( d = 1.19 g/mL, 362 mmol).…”

Section: Methodsmentioning

confidence: 99%

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [Mn^II(enH)(H₂O)][Cr^III(CN)₆]·H₂O

2008

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We report the synthesis, crystal structure, and thermal and magnetic properties of the two-dimensional achiral soft ferrimagnet [Mn(II)(enH)(H(2)O)][Cr(III)(CN)(6)].H(2)O (1), en = 1,2-diaminoethane, as well as the recyclability of the dehydration and rehydration and their influence on the crystal structure and its magnetic properties. Unlike [Mn(S-pnH)(H(2)O)][Cr(CN)(6)].H(2)O (2S, pn = 1,2-diaminopropane), which is a chiral (P2(1)2(1)2(1)) enantiopure ferrimagnet (T(C) = 38 K), 1 crystallizes in the achiral orthorhombic Pcmn space group, having a similar two-dimensional square network of Mn-Cr with bridging cyanide, and 1 behaves also as a soft ferrimagnet (T(C) = 42 K). X-ray diffraction experiments on a single crystal of 1 indicate a transformation from a single crystal to an amorphous phase upon dehydrataion and partial recovery of its crystallinity upon rehydration. The dehydrated phase 1-DP exhibits long-range ordering at 75 K to a ferrimagnetic state and coercive field at 2 K of 100 Oe, which are a higher critical temperature and coercive field than for the virgin sample (H(C) = 60 Oe). Thermogravimetric analyses indicate that the crystallinity deteriorates upon hydration-dehydration cycling, with persistence toward the amorphous phase, as also seen by magnetization measurements. This effect is associated with an increase of statistical disorder inherent in the dehydration-rehydration process. X-ray powder diffraction suggests that 1-DP may retain order within the layers but loses coherence in the stacking of the layers.

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Section: Methodsmentioning

confidence: 99%

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [Mn^II(enH)(H₂O)][Cr^III(CN)₆]·H₂O

2008

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“…8 K 3 [Cr(CN) 6 ] was prepared by the literature method. 9 Caution! Perchlorate salts of metal complexes with organic ligands are potentially explosive and should be handled in small quantities with great care.…”

Section: Preparationsmentioning

confidence: 99%

Crystal structure and magnetic behavior of a three-dimensional cyano-bridged assembly [CuL¹]₂[Cr(CN)₆]ClO₄·0.5H₂O (L¹ = 3,10-dipropyl-1,3,5,8,10,12- hexaazacyclotetradecane)

et al. 2004

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“…The complexity of the reaction chain precluded any kinetic measurement: however, it was qualitatively observed that cyanide loss becomes slower and slower as more ligands are removed, as in the course of the acid-induced aquation of Cr(CN) 6 3- …”

Section: Resultsmentioning

confidence: 99%

“…While cationic chromium(III) complexes of general formula Cr(NH 3 ) 5 X z + have been extensively investigated with regard to their thermal and photochemical ligand substitution reactions, much less analogous information is available for their anionic counterparts, Cr(CN) 5 X z - . The pentacyanochromates(III) with X = H 2 O, , OH - , , Me 2 SO, DMF (dimethylformamide), and MeCN have been identified as the products of thermolysis 1,3,4 or photolysis 2,5-7 of Cr(CN) 6 3- in the corresponding solvents, and that with X = NCS - has been separated in solution from mixtures of Cr(CN) 6 - n (NCS) n 3- anions formed by interaction of CN - with Cr(NCS) 6 3- . , However, obstacles to the study of these compounds have been the difficult isolation of adequate quantities and, sometimes, the instability toward CN - loss even in moderately acidic media . The only pentacyano complexes thus far obtained as solid salts are K 3 [Cr(CN) 5 (OH)]·H 2 O and K 2 [Cr(CN) 5 (NH 3 )], the latter prepared and photochemically characterized in this laboratory.…”

Section: Introductionmentioning

confidence: 99%

Pentacyano(pyridine)chromate(III): Synthesis, Characterization, and Photochemistry

1997

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The Cr(CN)(5)(py)(2)(-) anion (py = pyridine) has been prepared by acid-promoted methanolysis of Cr(CN)(6)(3)(-) followed by reaction with pyridine, isolated as the potassium salt, and characterized by absorption spectra (lambda(max): 403 and 256 nm in H(2)O; 411 nm in Me(2)SO) and phosphorescence, observed in Me(2)SO (lambda(max), 774 nm; tau = 56 &mgr;s at 20 degrees C) but not in H(2)O. In acid aqueous solution the complex decomposes stepwise to Cr(H(2)O)(5)(py)(3+); by contrast, the thermal reaction in Me(2)SO leads to Cr(CN)(5)(Me(2)SO)(2)(-) with first-order kinetics (k(25) = 9.8 x 10(-)(7) s(-)(1), DeltaH() = 138 +/- 8 kJ mol(-)(1)). Ligand-field (LF) band irradiation results in substitution of py and CN(-). The quantum yields, measured by ligand analysis, spectrophotometry, and HPLC, are as follows: Phi(py) = 0.08, Phi(CN) = 0.01 in H(2)O (pH 7.2, phosphate buffer) and Phi(py) = 0.04, Phi(CN) = 0.002 in Me(2)SO. The preference for py release obeys the prediction of the Vanquickenborne-Ceulemans, additive angular overlap model (AOM). A notable feature of this complex is that both types of ligands are pi acceptors, and the pi effect of py on bond labilization is evidenced by comparison with the photolysis of Cr(CN)(5)(NH(3))(2)(-). Irradiation of the intense UV absorption due to overlap of charge-transfer (CT) and pi --> pi, py localized transitions causes the increase of both quantum yields, suggesting the involvement of higher-energy states besides the LF ones. Co(sep)(3+) (sep = 1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane = sepulchrate) quenches the phosphorescence (k(q) = 1.6 x 10(9) M(-)(1) s(-)(1)) but has no effect on the photoreaction efficiencies: the photochemistry is thus inferred to originate entirely from the lowest quartet excited state(s) in competition with intersystem crossing. The marked solvent effects on the absorption spectrum, on the emission behavior, on the thermal reactivity, on the photolysis quantum yields, and, in particular, on the Phi(py)/Phi(CN) ratio, are discussed in terms of the proneness of the cyanide ligand to either protonation or hydrogen bonding and of solvent orientation toward anionic complexes.

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Cyanoaquochromium(III) Complexes: Isolation, Spectra, Aquation Reactions and Kinetics

Cited by 8 publications

References 11 publications

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [Mn^II(enH)(H₂O)][Cr^III(CN)₆]·H₂O

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [Mn^II(enH)(H₂O)][Cr^III(CN)₆]·H₂O

Crystal structure and magnetic behavior of a three-dimensional cyano-bridged assembly [CuL¹]₂[Cr(CN)₆]ClO₄·0.5H₂O (L¹ = 3,10-dipropyl-1,3,5,8,10,12- hexaazacyclotetradecane)

Pentacyano(pyridine)chromate(III): Synthesis, Characterization, and Photochemistry

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Cyanoaquochromium(III) Complexes: Isolation, Spectra, Aquation Reactions and Kinetics

Cited by 8 publications

References 11 publications

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [MnII(enH)(H2O)][CrIII(CN)6]·H2O

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [MnII(enH)(H2O)][CrIII(CN)6]·H2O

Crystal structure and magnetic behavior of a three-dimensional cyano-bridged assembly [CuL1]2[Cr(CN)6]ClO4·0.5H2O (L1 = 3,10-dipropyl-1,3,5,8,10,12- hexaazacyclotetradecane)

Pentacyano(pyridine)chromate(III): Synthesis, Characterization, and Photochemistry

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On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [Mn^II(enH)(H₂O)][Cr^III(CN)₆]·H₂O

On the Nature of the Reversibility of Hydration—Dehydration on the Crystal Structure and Magnetism of the Ferrimagnet [Mn^II(enH)(H₂O)][Cr^III(CN)₆]·H₂O

Crystal structure and magnetic behavior of a three-dimensional cyano-bridged assembly [CuL¹]₂[Cr(CN)₆]ClO₄·0.5H₂O (L¹ = 3,10-dipropyl-1,3,5,8,10,12- hexaazacyclotetradecane)