bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Study on the Acidic Properties and Catalytic Activities of TiO2, SiO2, Al2O3, SiO2–Al2O3, SiO2–TiO2, Al2O3–TiO2, and TiO2–SiO2–Al2O3
Authors: Sabu Kuzhunellil Raghavan Pillai , Rao Kalur Vijayachandra C , Nair Chandrathil Govindan Ramachandran 
Published: July 2006

Abstract
Investigations are carried out to have a systematic comparison of the acidic properties and catalytic activities of single oxide TiO2, SiO2, Al2O3, their binary oxides and the ternary oxide TiO2–SiO2–Al2O3. The acidity distributions are measured by using butylamine titration technique and the test reactions selected for the catalytic activity measurements are alkylation of toluene with 2-propanol and the dehydration of 2-propanol. The single oxides have only low acid strength and are not at all active in catalyzing the alkylation reaction, but are marginally active in the dehydration of 2-propanol. However the binary oxides SiO2–TiO2 and Al2O3–TiO2 of 10% by weight of TiO2 are found to contain very strong acid sites Ho≤−8.2 and are highly active catalysts in both the test reactions. But TiO2–SiO2–Al2O3 of 10% by weight of TiO2 showed the highest acid amount and the highest activity in the aikylation and dehydration reactions compared to the binary oxides. The acid amount and the catalytic activity of the ternary oxide increased with the increase of TiO2 content upto 50 mol% of TiO2 and then decreased. The ternary oxide containing 80 mol% of TiO2 is rich in weak acid sites. The increase of TiO2 content does not affect the selectivity.
Dynamics of Autoxidation of Aqueous Sulfur Dioxide in Aqueous Suspensions of Cadmium Oxide
Authors: Rani Ashu , Prasad D S N , Bhargava Rachna , Gupta Krishna Swarup 
Published: July 2006

Abstract
Autoxidation of S(IV), in buffered solutions,conforms the rate law (1). The increase in buffer concentration has a
R obsd=k5[CdO][S(IV)]2[H+]−1.22 (1)
rate decreasing effect. On the other hand, in unbuffered solutions the kinetics obey a different rate law (2).
R obsd=(k10+k11[CdO])[S(IV)][H+]−0.5 (2)
In both situations, the dissolution of CdO accompanies the autoxidation. A heterogeneous catalytic mechanism involving adsorption of both dioxygen and sulfur(IV) on the surface of CdO particle has been proposed.
Aryliminodimagnesium Reagents. XIX. Effects of Miscellaneous Metal Halides on Oxidative Self-Coupling of the Reagent, and on Its Condensation with Nitrobenzene. A New Preparative Route to o,o′-Dihydroxyazobenzene
Authors: Okubo Masao , Shiku Haruko 
Published: July 2006

Abstract
Fourteen metal halides (MXn) were each added to the solutions of aryliminodimagnesium (p-RC6H4N(MgBr)2, IDMg) in tetrahydrofuran, and the effect of MXn on relative yields of products was examined in the following three IDMg reactions: (A) oxidative coupling leading to symmetrical azobenzene, (B) condensation with nitrobenzene, and (C) condensation with o-hydroxy-substituted (o-HO) nitrobenzene. Reaction A was promoted by addition of CuCl2, and the yield of azoxybenzenes in reaction B was improved by addition of NiCl2 or CdCl2. Reaction C was similarly modified by addition of CdCl2 so as to improve the yield of o-HO-azoxybenzenes. Their acetyl derivatives underwent a facile photoinduced migration of azoxy oxygen and were successively hydrolyzed to afford bidentate chelating agents, o,o′-(HO)2-azobenzenes.
Complexations of New Pyridylazo Ligands with Ni(II), Zn(II), and Cd(II)
Authors: Huang Hu , Kai Fumiaki , Uragami Chiemi , Hirohata Masaaki , Chikushi Hiroaki , Yanaka Hisae , Honda Mayumi , Nakamura Masaaki 
Published: July 2006

Abstract
New ligands, 1-(3,5-dichloro-2-pyridyl-azo)-2-naphthol, 2-(3,5-dichloro-2-pyridyl-azo)-5-(dimethylamino) phenol, and 2-(3,5-dichloro-2-pyridyl-azo)-5-(dimethylamino)benzoic acid, were synthesized. Changes in the reduction potentials and electronic spectra of the ligands upon complexation with Ni(II), Zn(II), and Cd(II) were studied. The dissociation constants of the ligands and the stability constants of their metal(II) complexes are discussed.
Synthesis of 2,2,2-Trifluoroethylated Onium Salts of Nitrogen, Sulfur, and Phosphorus with (2,2,2-Trifluoroethyl)phenyliodonium Triflate
Authors: Umemoto Teruo , Gotoh Yoshihiko 
Published: July 2006

Abstract
Various 2,2,2-trifluoroethyl onium triflates were synthesized by treating tertiary amines, pyridines, quinoline, a triazole, sulfides, and a phosphine with (2,2,2-trifluoroethyl)phenyliodonium triflate. Sulfoxides and N-oxide were converted to the corresponding trifluoroethylated salts. As an application, CsF-treatment of (2,2,2-trifluoethyl)triphenylphosphonium triflate with an aldehyde was shown to produce a trifluoromethylated olefin.
Efficient Transformation of Methyl Propargyl Ethers into α,β-Unsaturated Ketones
Authors: Fukuda Yukitoshi , Utimoto Kiitiro 
Published: July 2006

Abstract
Methyl propargyl ethers, obtained from carbonyl compounds by successive treatment with an acetylide and MeI, were easily converted to the corresponding α,β-unsaturated ketone by regioselective hydration of acetylenic moiety followed by elimination of methanol under the catalytic action of Au(III).
Preparation and Crystal Data of the New Compounds Ag7MS6 (M=Ta and Nb)
Authors: Wada Hiroaki 
Published: July 2006

Abstract
The compounds Ag7TaS6 and Ag7NbS6 were prepared by a sealed silica tube method at 500°C for 4 d. They crystallize in the face-centered cubic system with the unit-cell dimensions of a=10.5139±0.0003 Å and a=10.5001±0.0006 Å, respectively. From the density measurements, it has been clarified that the unit cell contains four formula units.
Equilibrium and Kinetic Studies on Complex Formation Reaction between Crown Ethers and Bivalent Transition Metal Ions
Authors: Matsuyama Hideto , Arimura Takeo , Miyake Yoshikazu , Teramoto Masaaki 
Published: July 2006

Abstract
The complex formation reaction between crown ethers and bivalent transition metal ions was investigated. Although the obtained equilibrium constants were generally small, there was a case where the constant was larger than that for the crown ether–alkali metal system. From kinetic studies the reactions were found to obey the Eigen’s mechanism.
Synthesis and Reactions of Some New Pyridazinones
Authors: Ghani Essam Abdel 
Published: July 2006

Abstract
3-(p-Ethoxybenzoyl)acrylic acid (1) reacts with 3-methyl-1-phenyl-2-pyrazolin-5-one to give an addition compound 2. The condensation of 2 with hydrazine hydrate affords 4,5-dihydro-3(2H)-pyridazinone (3a). Reaction of 3a with dimethyl sulfate, diethyl sulfate, ethyl bromoacetate, POCl3, and P2S5 gave the N-substituted pyridazinones 3b–d, a dichloro derivative 5a, and a dithione 7. The behavior of the dichloro and the dithione derivatives was studied toward different reagents. The in vitro antibacterial screening reveals moderate activity against Gram-positive for compounds 3a and 3c while 4 and 7 are inactive.
Preparation and Properties of Heteropoly Molybdovanadate(V) Complexes
Authors: Himeno Sadayuki , Osakai Toshiyuki , Saito Atsuyoshi 
Published: July 2006

Abstract
Tetrabutylammonium salts of the mixed heteropoly molybdovanadate(V) anions, [Hx−1V(VxMo12−x)O40]4− (x=1–3) were prepared from a Mo(VI)–V(V)–CH3CN system at room temperature. These mixed heteropoly anions were distinguished by their voltammetric behavior; the anions with x=1, 2, and 3 were electroreduced by one-, two-, and three-electrons due to the peripheral V atoms at a glassy carbon electrode. The spectroscopic properties were also reported. Their formation conditions were compared with those of 12-molybdovanadate (V), [VMo12O40]3−, especially regarding the concentrations of Mo(VI), V(V), acid, and organic solvents, the nature of organic solvents, and the ionic strength of the system. It should be emphasized that the 12-molybdovanadate(V) and mixed molybdovanadate(V) complexes are not formed in the absence of organic solvents.
Crystal Structure of the Organic Metal (DMET)2BF4 with Two Columns along Two Crystallographic Axes
Authors: Ishikawa Yoshimitsu , Saito Kazuya , Kikuchi Koichi , Kobayashi Keiji , Ikemoto Isao 
Published: July 2006

Abstract
The crystal structure of (DMET)2BF4: 5,6-dihydro-2-(4,5-dimethyl-1,3-diselenol-2-ylidene)dithiolo[4,5-b] [1,4]dithiinium tetrafluoroborate (2:1), (C10H10S4Se2)2BF4, is determined. Crystal data: Mr=919.49, triclinic, P\bar1, a=7.032(2), b=7.812(3), c=27.502(11) Å, α=90.87(2), β=90.28(2), γ=106.22(2)°, V=1450.5(15) Å3, Z=2, Dx=2.11 Mg m−3, λ(Mo Kα)=0.71068 Å, μ=5.60 mm−1, F(000)=890, T=297 K, R=0.077 for 4600 reflections. Two crystallographically independent DMET molecules separately form columns along nearly perpendicular directions, and ordered BF4 anions are located between the DMET columns.
Benzo[b]cyclohept[e][1,4]oxazines IV. Synthesis and Properties of All Possible Benzoxazinotropones
Authors: Wakabayashi Hidetsugu , Kurihara Teruo , Ishikawa Sumio , Okada Joji , Nozoe Tetsuo 
Published: July 2006

Abstract
Five isomeric benzo[b]cyclohept[e][1,4]oxazin-6∼10-ones (hereafter refered to as benzoxazinotropones) and bromobenzoxazinotropones were prepared almost quantitatively by the hydrolysis of the corresponding mono-, di-, and tribromobenzo[b]cyclohept[e][1,4]oxazines with refluxing acetic acid. On the basis of spectral data and theoretical calculations, benzo[b]cyclohept[e][1,4]oxazin-6∼9(11H)-ones are believed to exist in the keto form. These compounds gave respective methoxy- and acetoxybenzo[b]cyclohept[e][1,4]oxazines when reacted with diazomethane and acetic anhydride. On the other hand, benzo[b]cyclohept[e][1,4]oxazin-10(11H)-one was found to exist in a stable, intermolecularly hydrogen-bonded form and did not form acetoxylated or methylated compounds. Possible reaction pathways for the formation of these products are discussed.
Behavior of the Excited Cis Singlet State of a One-Way Isomerizing Olefin. Further Insight into Potential Energy Surfaces of 1-(3,3-Dimethyl-1-butenyl)pyrene
Authors: Okamoto Hiroaki , Arai Tatsuo , Sakuragi Hirochika , Tokumaru Katsumi , Kawanishi Yuji 
Published: July 2006

Abstract
The decay processes of the excited singlet state and potential energy surfaces of 1-(3,3-dimethyl-1-butenyl)pyrene (BP) were investigated. A long-lived fluorescence from the cis isomer and involvement of a quantum chain process for one-way isomerization suggest that the isomerization on direct excitation proceeds in the triplet manifold after intersystem crossing at the cis conformation.
Structural Transition Behavior of Potassium Salts of Saturated Fatty Acids, CH3(CH2)nCO2K (n=14, 16, 18, 20)
Authors: Ishioka Tsutomu 
Published: July 2006

Abstract
The structural transition behavior of potassium soaps (99% purity), CH3(CH2)nCO2K (n=14, 16, 18, 20), having low water contents of less than 10 wt% was investigated by both DSC and vibrational spectroscopies. Nine phases from crystal (I&lt;80°C) to liquid crystal (260°C&lt;IX) were observed for n=14 and 16 by thermal measurements. An additional phase I′ (I&lt;I′&lt;II) was found for n=18 and 20. The structural changes of the alkyl chains accompanied by these transitions were investigated by using IR and Raman methods. With increase in temperature, the itensities of the IR methylene progressive bands which were characteristic of all-trans conformation decreased and conformational defect bands ascribed to gt-, gg-, and gtg′ conformations, were observed in phases I′, II, and III for n=14–20. These indicate the onset of a partial melting of the chains in these phases. At the transition from phase III to IV, the chains entered liquid-like conformations. The result was also confirmed by the Raman spectra.
Solvent Polarity Parameters of Supercritical Carbon Dioxide as Measured by Infrared Spectroscopy
Authors: Ikushima Yutaka , Saito Norio , Arai Masahiko , Arai Kunio 
Published: July 2006

Abstract
The solvent polarity parameters of supercritical carbon dioxide were determined as a function of the temperature and pressure within the ranges 318–353 K and 5.85–28.5 MPa. An infrared (IR) spectroscopic technique has been employed to determine the values of π* dipolarity/polarizability and the Lewis basicity parameter BMeOD by measuring the transitions in the IR absorption wavelength of functional groups (such as C=O and O–H···BA, where BA is a hydrogen-bond acceptor), in supercritical carbon dioxide. Ultraviolet/visible (UV/vis) spectroscopy was used to determine the value of the Kamlet-Taft’s solvatochromic acidity partameter, α. The BMeOD-value was enhanced with density, but was very small at the temperatures and pressures examined, almost the same as that for hexane. The α-value tended to be dependent on density at lower pressures, but was remarkably smaller compared with those for alcohols. The π*-value significantly increased with an increase in the density, becoming more negative at higher temperatures above 10 MPa. Furthermore, the ET(30)-value was estimated by using the determined π*-value. A reliable ET(30)-value for supercritical carbon dioxide has been obtained.
Selective Isomerization of 1,5-Cyclooctadiene to 1,4-Cyclooctadiene Catalyzed by Bis(acetylacetonato)nickel–Triethyldialuminum Trichloride–Phosphorus Ligand
Authors: Sakakibara Yasumasa , Yamamoto Isao , Sasaki Ken , Sakai Mutsuji , Uchino Norito 
Published: July 2006

Abstract
The isomerization of 1,5-cyclooctadiene (1,5-COD) with Ni(acac)2–Et3Al2Cl3–phosphorus ligand (Ni : Al2 : P=1 : 10 : 3) was first examined with varying P ligands in toluene in order to find suitable conditions for the formation of 1,4-COD. The product distribution depended largely on the P ligands. For several phosphites possessing very strong π-acceptor properties, the main product was 1,4-COD. In particular, the less-bulky bicyclic phosphite, 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane (L-3) was very effective and gave 1,4-COD in a high selectivity of 93% at 66% conversion (1,5-COD/ Ni=500, molar ratio) by employing a low temperature of −30°C. However, the reaction stopped before reaching completion because the catalyst was deactivated by the accumulation of 1,4-COD product. The conversion, depending on the 1,5-COD/toluene ratio (volume) rather than the 1,5-COD/Ni ratio, increased with a decrease in the 1,5-COD/ toluene ratio and was 66–69% at a ratio of 0.19. On the other hand, the catalyst (P: L-3) was much less active for 1,4-COD than for 1,5-COD and was deactivated quickly under the same reaction conditions. This appeared to result in a high selectivity of 1,4-COD in the isomerization of 1,5-COD. The mechanistic implications of the experimental results are discussed.
Ortho Lithiation of 2-Hydroxymethyl-1,4,5,6,8-pentamethoxynaphthalene, a Supplement
Authors: Tanoue Yasuhiro , Terada Akira 
Published: July 2006

Abstract
The structures of the products in our previous report “One-Pot Ortho Hydroxylations of 2-(1-Hydroxyalkyl)-naphthalenes and (1-Hydroxyalkyl)benzenes” were reexamined by 13CNMR spectra and part of our previous interpretation will be corrected here. The lithiations of 2-(1-hydroxyalkyl)-1,4,5,6,8-pentamethoxynaphthalenes occurred at the 7-position, and not at the 3-position as we reported.
Vinyl Polymers Bearing a Pyrrole Ring. II. 5,10,15,20-Tetraphenylporphyrins with a Substituent-Bearing Vinyl Group at the Pyrrole Residue and Their Zinc Complexes
Authors: Kamogawa Hiroyoshi , Nakata Takuharu , Komatsu Sei 
Published: July 2006

Abstract
5,10,15,20-Tetraphenylporphyrins (Por) with a styrenic double bond-bearing substituent attached at the pyrrole residue with an amide or ester spacer were synthesized starting with 3-substituted pyrroles. Free radical copolymerization of ZnPor, prepared from Por, with 1-vinyl-2-pyrrolidone gave more favorable results than did Por.
X-Ray Crystallographic Analysis of Methyl (1S,2R,5R,6S,7R)-5,6-Dimethyl-2-(ω-camphanoyloxy)bicyclo[4.3.0]nonane-7-carboxylate. Revision of the Absolute Configurations of the Liverwort Sesquiterpenoids (−)-Chiloscyphone and (+)-Chiloscypholone
Authors: Tori Motoo , Hasebe Takeshi , Asakawa Yoshinori , Ogawa Keiichiro , Yoshimura Shin 
Published: July 2006

Abstract
The X-ray analysis of the title compound has been carried out to give unambiguous assignment of the absolute configurations of the liverwort sesquiterpenoids (−)-chiloscyphone and (+)-chiloscypholone, each for which the enantiomerically opposite configurations had been assigned in the previous report.
Reductive Deacetoxylation of Allylic Acetates Using Hexacarbonylmolybdenum(0)
Authors: Masuyama Yoshiro , Maekawa Kazunobu , Kurihara Toshiyuki , Kurusu Yasuhiko 
Published: July 2006

Abstract
Aliphatic allylic acetates were reduced to alkenes with hexacarbonylmolybdenum(0) in refluxing dioxane under nitrogen atmosphere. These reactions were accelerated by the addition of H2O. 1-Aryl- or 3-arylallyl acetates caused deacetoxylative allylic homocoupling under the same conditions.
Luminescence and Circularly Polarized Luminescence of Mononuclear and Binuclear Chromium(III) l-Alaninato Complexes
Authors: Tsubomura Taro , Ohkouchi Iwao , Morita Makoto 
Published: July 2006

Abstract
Luminescence and circularly polarized luminescence (CPL) spectra were investigated at low temperatures in order to clarify the chiroptical and electronic structures of monomeric and dimeric chromium(III) alaninato complexes. In the monomeric complexes, [Cr(l-(or d-)ala)3]·H2O, R1 and R2 lines of opposite spectral signs were found in the CPL spectra. The signs and relative intensities of the peaks were found to be comparable with circular dichroism (CD) spectra by employing theoretical arguments based on a strong crystal field theory. In the case of hydroxo-bridged dimeric complexes, [Cr2(OH)2(l-(or d-)ala)4]·3H2O, although the luminescence spectra of exchange-coupled pair states were clearly observed with a deduction of reasonable exchange interaction parameters, the CPL spectral components were not discernible because of the meso-type structure.
Effect of ZnO Addition on Cobalt–Alumina Interaction Species
Authors: Okamoto Yasuaki , Adachi Toshinori , Maezawa Akinori , Imanaka Toshinobu 
Published: July 2006

Abstract
The effect of ZnO addition on cobalt–alumina interaction modes was studied using TPR and XPS. It was found that the addition of 2 wt% ZnO markedly affects the distribution of the cobalt species in CoO/Al2O3 (5 wt% CoO): cobalt–alumina surface interaction species are removed and migration of cobalt into an alumina subsurface phase is promoted by ZnO. A formation of Co–Zn–O mixed oxide is proposed for ZnO–CoO/Al2O2O3 at high ZnO content. The dispersion and distribution of ZnO on Al2O3 are also strongly modified by the presence of cobalt.
The Reaction of (Arylthio)trimethylstannanes with 1-Aryl-1-bromoethanes: Effect of Substituent on the Process Shifting from Unimolecular to Bimolecular Substitution
Authors: Kozuka Seizi , Nakamura Hisashi 
Published: July 2006

Abstract
A kinetic study has been conducted on the reaction of (arylthio)trimethylstannanes with 1-aryl-1-bromoethanes. The reaction of the arylbromoethane bearing an electron-donating substituent was found involving unimolecular ionization of the arylbromoethane. The other reactions, however, were found to be second-order reactions. The nature of the second-order reactions was shifted from one involving unimolecular ionization as the minor process, to a clear bimolecular nucleophilic reaction, according to the electron-withdrawing nature of the substituents on the arylbromoethanes.
Local Structure of Polyethylene Glycol–Nal Solid Polyelectrolyte as Studied by 13C and 23Na NMR
Authors: Ueda Takahiro , Ohki Hiroshi , Nakamura Nobuo , Chihara Hideaki 
Published: July 2006

Abstract
13C CP/MAS NMR, 23Na powder NMR, and 23Na two dimensional nutation NMR were applied to complexes of Nal with polyethylene glycol (PEG) and tetraethylene glycol (TEG) to study the conformation of the polyethers and local structure around the Na+. 13C chemical shift data suggest strongly that the polyether chains assume the gauche conformation in the complexes. 23Na NMR spectrum of TEG–Nal complex gave a broad asymmetric line; simulation of the line shape led to e2Qq⁄h=590 kHz and η=0.7. No significant temperature dependence of the line shape was observed between 200 K and room temperature. For PEG–Nal complex e2Qq⁄h and η were estimated to be about 320 kHz and 0.7, respectively, from the nutation spectrum. On the basis of the above results, new model structures of PEG–Nal complex were presented.
Combined Temperature-Programmed Reduction (TPR)- Temperature-Programmed Desorption (TPD) Study of Supported Platinum Catalysts
Authors: Ebitani Kohki , Hattori Hideshi 
Published: July 2006

Abstract
Successive temperature-programmed desorption (TPD) after temperature-programmed reduction (TPR) (Combined TPR-TPD) was performed in order to characterize supported platinum catalysts (Pt/SiO2, Pt/Al2O3, Pt/ZrO2 and Pt/TiO2) as well as to judge the validity of the apparent TPR profiles. In successive H2-TPD runs obtained after cooling in the absence of hydrogen from 450°C to room temperature, the hydrogen desorption peak was observed only for the Pt/TiO2 sample, indicating that the hydrogenic species were kept on Pt/TiO2 sample, while no hydrogenic species were retained on the other samples after TPR up to 450°C. For both Pt/Al2O3 and Pt/TiO2 samples, hydrogen spillover seemed to proceed. Hydrogen incorporation during TPR was greater for Pt/TiO2 than for the others. This hydrogen spillover causes an overestimation of the consumed H2/Pt value determined by the apparent TPR profile for Pt/TiO2. For Pt/SiO2 and Pt/ZrO2 samples, the apparent TPR profiles were mostly due to a reduction of the supported Pt oxides. For the Pt/TiO2 sample, the hydrogen incorporation/emission at different temperatures during TPR was investigated. To generate SMSI states, desorption of the spiltover hydrogen is suggested to play a significant role; the role of hydrogen incorporation/emission in the generation of SMSI states is also discussed.
X-Ray, Electrical and Catalytic Studies of the System CoFe2O4–Co2TiO4
Authors: Dube Gulabshankar Ramkhelawan , Darshane Vishnu Shivram 
Published: July 2006

Abstract
The system Co1+xFe2−2xTixO4 has been studied with a view to investigating the cation distribution and to correlate the catalytic behavior of spinel with electrical and structural properties. To investigate cation distribution, techniques like X-ray diffraction, electrical conductivity, and thermo emf. have been used. The catalytic evaluation was carried out in the temperature range of 473–673 K using benzyl alcohol as a probe molecule. Our results show CoFe2O4 to be better catalyst for benzyl alcohol decomposition compared to Co2TiO4 or pure oxides of the system.
Association of Tris(acetylacetonato)chromium(III) with Chlorinated Phenols in the Liquid–Liquid Partition System
Authors: Katsuta Shoichi , Imura Hisanori , Suzuki Nobuo 
Published: July 2006

Abstract
The liquid–liquid partition behavior of tris(acetylacetonato)chromium(III) ([Cr(acac)3]) between heptane and 0.10 mol dm−3 aqueous sodium perchlorate solutions has been studied in the presence of a series of chlorinated phenols (HA) at 298.2 K. A large enhancement of the partition coefficient of [Cr(acac)3] with HA has been observed, e.g., it rises by about 1000-fold in the presence of 0.02 mol dm−3 3,5-dichlorophenol in the organic phase. This effect is ascribable to the association of [Cr(acac)3] with HA in the organic phase. From a partition-equilibrium analysis, the association complexes have been identified as being [Cr(acac)3]·iHA (i=1,2), and the association constants (βass,i) determined. The βass,i, value increases with an increase of the acid-dissociation constant of HA in the family of HA with the same combination of substituents at the 2,6-positions, i.e., the association is due to hydrogen bonding of the hydroxyl hydrogen atom of HA to [Cr(acac)3]. A linear free-energy relationship has been found between the βass,i, values of [Cr(acac)3] and those of [Co(acac)3] previously reported.