bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal and Molecular Structures of Hypervalent Thia/Selena-pentalenes
Authors: Iwasaki Fujiko , Manabe Noriko , Nishiyama Hideyuki , Takada Kiwamu , Yasui Masanori , Kusamiya Motoyuki , Matsumura Noboru 
Published: June 2006

Abstract
X-Ray structure analyses were performed on the 2,3,4,5-tetrahydro-3,4-dimethylene-2,5-bis(4-chlorophenylimino)-1,6,6aλ4-trithia-3,4-diazapentalene (5), 2,5-bis(4-chlorophenylimino)-6aλ4-thia-1,6-diselena-3,4-diazapentalene derivative (6) and 2,5-bis(phenylimino)-1,6-dithia-6aλ4-selena-3,4-diazapentalene derivative (7). The lengths of the S–S bonds (mean value of 2.401 Å) for 5 and those of the Se–S bonds (mean value of 2.501 Å) for 6 and 7 are longer than that of the normal S–S or Se–S single bond (2.08 and 2.21 Å for S–S and Se–S bonds, respectively) by about 15%, which shows the hypervalent character of these S–S or Se–S bonds. In molecule 5, a difference in the two S–S bonds (2.488 and 2.314 Å) is considered to be a reflection of the feature of a weak hypervalent bond, which is very liable with effects of the environment, such as substituents or packing. The same tendency was observed for molecule 6. The crystal structures of 5 and 6, both of which are p-Cl-phenylimino derivatives, are isomorphous with each other. The crystal structure of 7, a phenylimino derivative, is different from those of 5 and 6, and two Se–S bonds of 7 are almost similar. The diffraction intensities of 5 were measured by a Weissenberg-diffractometer with imaging-plates, because only very small crystals were obtained, the intensities of which could not be measured by a conventional four-circle diffractometer with a rotating anode generator.
Structures and Formation Mechanism of Novel Metal–Carbene Complexes Derived from Hypervalent Thiadiselenadiazapentalenes
Authors: Iwasaki Fujiko , Nishiyama Hideyuki , Yasui Masanori , Kusamiya Motoyuki , Matsumura Noboru 
Published: June 2006

Abstract
2,3,4,5-Tetrahydro-3,4-dimethylene-2,5-bis(4-chlorophenylimino)-6aλ4-thia-1,6-diselena-3,4-diazapentalene (6), which contains a hypervalent sulfur atom, has been found to give novel complexes by treating with [Pt(PPh3)4], [Pd(PPh3)4], and [RhCl(PPh3)3]. X-Ray investigations have revealed that the resultant complexes are novel metal–carbene complexes: {1,1′-(perhydroimidazole-1,3-diyl-κC2)bis[(4-chlorophenylimino)methaneselenolato-κ2SeSe′]}(triphenylphosphine)platinum(II) (8), {1,1′-(perhydroimidazole-1,3-diyl-κC2)bis[(4-chlorophenylimino)methaneselenolato-κ2SeSe′]}(triphenylphosphine)palladium(II) (9), and trans(P,P′)-(chloro){(perhydroimidazole-1,3-diyl-κC2)bis[(4-chrolophenylimino)methaneselenolato-κ2SeSe′]}bis(triphenylphosphine)rhodium(III) (10). The central sulfur atom in 6 was substituted by a metal atom to form metal–selenium bonds in the resultant metallapentalene framework. The structure of complex (11), obtained from thiatetraazapentalene-2,5-diselone with [Pd(PPh3)3], was also determined by an X-ray analysis. This complex was also a metal–carbene complex with a metallapentalene framework: {1,1′-(perhydropyrimidine-1,3-diyl-κC2)bis[(4-chlorophenylimino)methaneselenolato-κ2SeSe′]}(triphenylphosphine)palladium(II) (11). The final R values are 0.038, 0.034, 0.046, and 0.032 for the 4494, 4234, 3919, and 4451 observed reflections for 8, 9, 10, and 11, respectively. The fact that similar metal–carbene complexes with a metallapentalene framework were obtained from both thiadiselenadiazapentalenes and thiatetraazapentalene-2,5-dithione/diselones confirms the previously proposed formation mechanism of these metal–carbene complexes.
Acceleration of Deswelling of Poly(N-isopropylacrylamide) Hydrogel by the Treatment of a Freeze-Dry and Hydration Process
Authors: Kato Norihiro , Takahashi Fujio 
Published: June 2006

Abstract
The deswelling rate of a thermally-sensitive gel consisting of poly(N-isopropylacrylamide) crosslinked by 4% N,N′-methylenebisacrylamide (MBA) was accelerated at above the lower critical solution temperature (LCST) by the treatment of a freeze-dry and hydration process (freeze-dry treatment); it was roughly 102 times faster than the gel without a freeze-dry treatment. The values of the apparent activation energy (Ea’s) for the conventional gel crosslinked by 2 and 4% MBA was roughly 140 kJ mol−1 each, and those for freeze-dry treated gel crosslinked by 2, 4, and 10% MBA were 24, 25, and 12 kJ mol−1, respectively. An SEM photomicrograph showed that the freeze-dry treatment made the gel porous. The freeze-dry treated gel exhibited a weaker shrinking force, and showed easy expansion compared with the conventional gel. An expansion of the diffusion area of water and a decrease of the thickness of the surface layer for a macroporous gel could be the reason for the increase in the deswelling rate.
Determination of the Acid Strength of Binary Oxide Catalysts Using Temperature-Programmed Desorption of Pyridine
Authors: Satsuma Atsushi , Westi Yenni , Kamiya Yuichi , Hattori Tadashi , Murakami Yuichi 
Published: June 2006

Abstract
The temperature-programmed desorption of pyridine (Py-TPD) was performed for measuring the acid strength and acid amount of binary oxide catalysts. First, the optimum measurement conditions were determined by comparing the TPD spectra with the infrared spectra of adsorbed pyridine measured under the same conditions in order to minimize the shift in the desorption temperature and contribution of physically absorbed and/or weakly held pyridine. The following conditions were found to be optimum: purging at 423 K for 2 h, W/F (W, sample weight; F, flow rate of the carrier) of 100 mg/150 cm 3 min −1, and a heating rate of 5 K min−1. This method was applied then to a series of binary mixed oxide catalysts. The amount of desorbed pyridine was 15—24% of the full coverage of pyridine on the catalyst surface with few exceptions. The highest acid strength, determined from the Py-TPD spectra, was well-correlated to that determined from a color change of Hammett indicators. The potential of the Py-TPD for determining the acid strength and the acid amount on binary oxide catalysts is discussed.
Excitation Energy Dependence of Transient Absorptions of [N,N′-o-Phenylenebis(salicylideneaminato)]cobalt(II) in Dmf Solution
Authors: Ohashi Yukako 
Published: June 2006

Abstract
[N,N′-o-Phenylenebis(salicylideneaminato)]cobalt(II), [Co(saloph)], forms two solvated complexes in the dmf solution; that is [Co(saloph)]·dmf at higher temperature and [Co(saloph)]·2dmf at lower temperature. The transient absorptions of the two species were measured in the present work with irradiation of the 532 nm- and 355 nm-light. For [Co(saloph)]·2dmf, the intensity change of the transient absorption induced by the 532 nm-excitation was ca. 5 times larger than that induced by the 355 nm-excitation, although the spectra was the same. By contrast, for the transient absorption of [Co(saloph)]·dmf, no dependence on the excitation wavelength was found with respect to the spectra, the absorption intensity or the decay rates. A quantum calculation of the electronic excited states was carried out by ZINDO model. Taking into consideration the calculated results, the observed differences between the excitation-wavelength dependence of the transient absorptions are discussed.
Mechanism of Isotopic Exchange for Cs+/*Cs+, Sr2+/*Sr2+, and Co2+/*Co2+ on Cerium(IV) and Tin(IV) Antimonates Particles
Authors: El-Naggar Ibrahim Mohamed , Zakaria Essam Saleh , Aly Hisham Fouad 
Published: June 2006

Abstract
Self-diffusion coefficients () for Cs+, Sr2+, and Co2+ ions in cerium(IV) antimonate and tin(IV) antimonate have been investigated under conditions of particle diffusion and the limited batch technique for these ions in solutions of different acidity. The effect of heat treatment on the rate of isotopic exchange reactions on both materials was also studied. Values for the diffusion coefficients, activation energy, and entropy of activation have been evaluated. The data obtained have been compared with those reported for other organic and inorganic exchangers, which give some information regarding the mechanism of ion exchange on the surface of the ion exchange materials.
Spectral Studies and In Vitro Antimicrobial Activity of New Organotin(IV) Complexes of Schiff Bases Derived from Amino Acids
Authors: Nath Mala , Yadav Rakesh 
Published: June 2006

Abstract
Some new di- and triphenyltin(IV) complexes of the general formulae Ph2SnL and Ph3SnL′, where H2L/HL′ = Schiff bases derived from the condensation of 2-hydroxy-1-naphthaldehyde (H2L) and benzaldehyde (HL′) with glycine (H2L-1/HL′-1), Dl-α-alanine (H2L-2/HL′-2), l-methionine (H2L-3/HL′-3), Dl-valine (H2L-4/HL′-4), d-phenylalanine (H2L-5/HL′-5), 2-aminobutyric acid (H2L-6/HL′-6), and l-leucine (H2L-7/HL′-7), have been synthesized and characterized by elemental analyses, molar conductance, electronic, infrared and far-infrared, multinuclear magnetic resonance (1H, 13C, and 117Sn), and 119Sn Mössbauer studies. Thermal decomposition of a few complexes using TG, DTG, and DTA techniques indicates the formation of SnO2 as a residue. The complexes have also been tested in vitro against bacteria [Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus Penicillin resistance (2500 units)] and fungi [Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii, Trichophyton mentagrophytes, and Aspergillus fumigatus]. All of the complexes show remarkable activity.
Fluorescent Sensors for Molecules. Guest-Responsive Monomer and Excimer Fluorescence of 6A,6B-; 6A,6C-; 6A,6D-; and 6A,6E-Bis(2-naphthylsulfonyl)-γ-cyclodextrins
Authors: Hamada Fumio , Minato Shingo , Osa Tetsuo , Ueno Akihiko 
Published: June 2006

Abstract
Flexible hosts, 6A,6B-; 6A,6C-; 6A,6D-; and 6A,6E-bis(2-naphthylsulfonyl)-γ-cyclodextrins (γ-1, γ-2, γ-3, and γ-4, respectively) were used as fluorescent sensors with which a variety of organic compounds were detected by naphthalene excimer and monomer emissions. In a 10 vol% ethylene glycol aqueous solution, γ-1 exhibits almost pure monomer fluorescence while γ-2, γ-3, and γ-4 exhibit both monomer and excimer emissions. The intensities of the emissions changed upon addition of guest species, particularly in the case of γ-2 and γ-3, and the guest-induced intensity variations were used as sensitivity factors of the sensors. When (−)-borneol (5), cyclohexanol (6), cyclododecanol (7), and 1-adamantanecarboxylic acid (8) were added to each host solution, γ-2, γ-3, and γ-4 increased the excimer emission intensity but decreased the monomer one, the absolute intensity variations being 6 &lt; 5 ≈ 8 &lt; 7. When geraniol (9), nerol (10), and (−)-menthol (11) were added, the hosts decreased intensities in both monomer and excimer emissions for 9 and 10 while their emission variations for 11 were similar to those of 5. For steroids such as cholic acid (12), deoxycholic acid (13), chenodeoxycholic acid (14), and ursodeoxycholic acid (15), γ-4 showed depression in the excimer emission and enhancement in the monomer one while γ-2 and γ-3 showed complicated features in which the excimer emission was enhanced with the order of 15 &lt; 14 &lt; 13 ≈ 12 but the monomer one was depressed or enhanced depending on the hosts. All these data demonstrate that the hosts can be used as sensors for molecular recognition.
Kinetics and Mechanism for the Formation and Dissociation Reactions of 21-(4-Nitrobenzyl)-5,10,15,20-tetrakis(4-sulfonatophenyl)-23H-porphyrinatozinc(II) and -cadmium(II)
Authors: Tabata Masaaki , Ishimi Hiroaki 
Published: June 2006

Abstract
The incorporation reaction of zinc(II) and cadmium(II) into 21-(4-nitrobenzyl)-5,10,15,20-tetrakis(4-sulfonatophenyl)-23H-porphyrin (NO2Bz(Htpps)4−; HP4−) and the dissociation reaction of the metalloporphyrins ([MP]3−) have been studied spectrophotometrically at I = 0.1 mol dm−3 (NaNO3). The formation rate of the metalloporphyrins is expressed by the following equation: d[MP3−]/dt = kfM[M2+][HP4−]+kfMOH[MOH+][HP4−]-kdMP[MP3−][H+]. The rate constants and the activation parameters of the reaction were found to be kfZn = (4.86 ± 0.06) × 102 mol−1 dm3 s−1 (25 °C), ΔH‡ = 62.1 ± 1.6 kJ mol−1, and ΔS‡ = 14.8 ± 5.3 J mol−1 K−1; kfZnOH = (6.39 ± 0.14) × 103 mol−1 dm3 s−1 (25 °C), ΔH‡ = 22.8 ± 0.9 kJ mol−1, and ΔS‡ = −90.2 ± 3.1 J mol−1 K−1; kdZnP = 122.3 ± 2.3 mol−1 dm3 s−1 (25 °C), ΔH‡ = 19.8 ± 2.2kJ mol−1, and ΔS‡ = −139 ± 18 J mol−1 K−1 for zinc(II) and kfCd = (1.17 ± 0.02) × 105 mol−1 dm3 s−1 (25 °C), ΔH‡ = 42.5 ± 1.3 kJ mol−1, and ΔS‡ = −5.3 ± 4.2 J mol−1 K−1; kdCdP = (2.51 ± 0.04) × 107 mol−1 dm3 s−1 (25 °C), ΔH‡ = 14.6 ± 0.5 kJ mol−1, and ΔS‡ = −54.3 ± 1.7 J mol−1 K−1 for cadmium(II).
Nitrobenzyl group lowers the basicity of porphyrin. The effect of the lowered basicity appeared strongly in the following order for the formation rate and equilibrium constants of the metalloporphyrins: Cd2+ &lt; Zn2+ &lt; [ZnOH]+. A hydrogen-bond formation between [ZnOH]+ and the pyrrole proton in NO2Bz(Htpps)4− is proposed for the reaction based on the larger rate constant than the water-exchange rate constant enhanced by the hydroxide ion bound to zinc(II), the small activation enthalpy, the negative activation entropy, and the dependence of porphyrin basicity.
Polarographic Study on the Stabilization of Copper(I) State by Macrocyclic Triamine with an Aid of Monodentate π-Ligand
Authors: Kodama Mutsuo 
Published: June 2006

Abstract
Formation equilibria of ternary copper(I)-macrocyclic triamine ([11]aneN3, [12]aneN3, iso[12]aneN3, and [12]aneN3S) complexes with monodentate π-ligand (SCN−, CH3CN, or imidazole) were studied by the polarographic method. The copper(I)-macrocyclic triamine complexes in solutions containing an excess monodentate π-ligand were found to produce a polarogram consisting of two separate reduction steps of equal height. The chemical equilibria for the formation of the 1 : 1 : 1 ratio copper(I) mixed ligand complexes including macrocyclic triamine and π-ligand were determined by studying the effects of solution pH and concentrations of macrocyclic triamine and π-ligand on the half-wave potential of the 2nd reduction step, which appears at more negative potentials. The eleven-membered macrocyclic triamine, [11]aneN3, forms the most thermodynamically stable copper(I) mixed ligand complex, [CuIL(A)]1−b. The formation constants for 1 : 1 : 1 ratio copper(II), macrocyclic triamine, and monodentate π-ligand were determined potentiometrically by studying the effects of SCN−, CH3CN, or imidazole concentration on the formation equilibrium of copper(II)-macrocyclic triamine complexes.
Synthesis and Characterization of Water-Soluble, All-Inorganic Composition, Dawson-Type Trisubstituted Heteropolytungstates. Effect of Alkali Metal Countercations (Li, Na, K, and Cs) on the P2W15Nb3O629− Polyoxoanion
Authors: Nomiya Kenji , Nozaki Chika , Miyazawa Kohji , Shimizu Yasushi , Takayama Toshio , Nomura Keiichi 
Published: June 2006

Abstract
The water-soluble form of the Dawson-type trisubstituted tungstoheteropolyanion, B-α-P2W15Nb3O629−, was synthesized as its nona alkali-metal salts of Li, K, and Cs. Analytically pure compounds, obtained as homogeneous colorless solids, had nonahydrate for the nonalithium (Li9) salt, tetrahydrate for the nonasodium (Na9) salt, trihydrate for the nonapotassium (K9) salt and trihydrate for the nonacaesium (Cs9) salt, respectively, after each was dried overnight at room temperature under 10−3—10−4 Torr. TG/DTA analyses show that they can be made with 25 water for the Li9 salt, 23 water for the Na9 salt, 9 water for the K9 salt, and 8 water for the Cs9 salt under atmospheric conditions. A compositional characterization was accomplished by complete elemental analyses and TG/DTA, and structural characterization was achieved by a combination of FT-IR and variable-temperature solid-state 31P NMR and by both 31P and 183W NMR measurements at room temperature in D2O and DMSO-d6 solutions. The amount of hydrated waters, solubility in solvents and ease of crystallization were significantly influenced by the alkali-metal countercations. These cation-dependent properties are useful for selecting polyoxoanion precursor favorable to the crystallization of P2W15Nb3O629−-supported organometallic complexes. The effects of the cations (Li, K, Na, and Cs) on the P2W15Nb3O629− were observed as different hydrated structures of the polyoxoanion and its cation-dependent thermal stability in the solid state by a combination of TG/DTA and FT-IR measurements, and also as a spectral change of the downfiled 31P signal due to interactions of the polyoxoanion with the countercations and/or with hydrated waters by variable-temperature (VT) solid-state GHD/MAS 31P NMR spectroscopy.
Solvent Extraction of Several Divalent Metal Ions with 4-Isopropyltropolone into Chloroform in the Absence and Presence of Trioctylphosphine Oxide
Authors: Sekine Tatsuya , Ninomiya Ichiro , Tebakari Masayuki , Noro Junji 
Published: June 2006

Abstract
The solvent extraction of divalent metal ions, manganese(II), cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) in aqueous 0.1 mol dm−3 sodium nitrate solutions with 2-hydroxy-4-(1-methylethyl)-2,4,6-cycloheptatrien-1-one (4-isopropyltropolone; Hipt) into chloroform was studied in the absence and presence of trioctylphosphine oxide (TOPO). When the concentration of metal ions (M2+) was 1 × 10−5 to 1 × 10−4 mol dm−3 in the initial aqueous solutions, the extracted species of the metal ions in the absence of TOPO were only the mononuclear complex, M(ipt)2, with copper(II); these species were both the mononuclear complex, M(ipt)2, and the mononuclear self-adduct complex, M(ipt)2·Hipt, with zinc(II); they were both the mononuclear complex, M(ipt)2, and the dinuclear complex, M2(ipt)4, with cobalt(II) and cadmium(II); and they were predominantly the dinuclear complex, M2(ipt)4, with nickel(II) and manganese(II). It was also found that the extraction of manganese(II), cobalt(II), nickel(II), zinc(II), and cadmiun(II) was enhanced when TOPO was added into the organic phase. This was explained in terms of the formation of mononuclear adduct complex, M(ipt)2TOPO, from M(ipt)2, M(ipt)2·Hipt, and/or M2(ipt)4. The extraction constants for those species were determined. The extractability and the tendency to form dinuclear complexes are discussed.
Asymmetric Synthesis of Organosilicon Compounds Using a C2 Chiral Auxiliary
Authors: Kobayashi Kimiko , Kato Takayuki , Unno Masafumi , Masuda Shinji 
Published: June 2006

Abstract
Optically active silanes were synthesized by a novel asymmetric synthesis which involved the diastereoselective ring-opening reaction of 1,3-dioxa-2-silacycloheptanes bearing a C2 chiral auxiliary with Grignard reagents, followed by a lithium aluminum hydride (LiAlH4) reduction. (R)-Ethylmethylphenylsilane and (R)-methylphenylpropylsilane were derived in 93%ee and 98%ee, respectively. The preparation of the other optical silanes is also described. The maximum rotations of some of them have been determined by 1H NMR and/or capillary GC methods. A mechanism for a diastereoselective ring-opening reaction is proposed based on the stereochemical results.
Substituent Effects on the Solvolysis of 1,1-Diphenyl-2,2,2-trifluoroethyl Tosylates: Comparison between Symmetrically Disubstituted and Monosubstituted Systems
Authors: Fujio Mizue , Morimoto Hiroshi , Kim Hyun-Joong , Tsuno Yuho 
Published: June 2006

Abstract
The solvolysis rates of 1-(substituted phenyl)-1-phenyl-2,2,2-trifluoroethyl and 1,1-bis(substituted phenyl)-2,2,2-trifluoroethyl tosylates or bromides were conductimetrically measured at 25.0 °C in 80% aqueous ethanol. The substituent effects on these solvolyses were analyzed on the basis of the Yukawa–Tsuno equation. The former monosubstituted diphenyl system did not show a single linear Yukawa–Tsuno correlation; a bilinear correlation was observed with ρ = −4.33 and r = 1.26 for substituents more deactivating than p-methyl, and ρ = −6.08 and r = 1.45 for the substituent range more reactive than 3,4-dimethyl. The bilinear correlation was explicable in terms of the changing coplanarity of the respective benzene rings.
On the other hand, the symmetrically disubstituted diphenyl substrates gave an excellent linear Yukawa–Tsuno correlation for the whole substituent range with a ρ value of −8.3/2 and an r value of 1.19. The substituent effect correlation leads to the conclusion that the two aryl rings in this symmetrical system remain in the equivalent propeller-shape conformation with respect to deviations from coplanarity with the carbenium ion center in the transition state.
New Efficient Synthesis of a Biosynthetic Precursor of Lipid A
Authors: Oikawa Masato , Wada Akira , Yoshizaki Hiroaki , Fukase Koichi , Kusumoto Shoichi 
Published: June 2006

Abstract
A biosynthetic precursor of lipid A has been synthesized by an improved efficient method. Two appropriately modified acyl-substituted glucosamine units were synthesized from d-glucosamine using (R)-3-(benzyloxy)tetradecanoic acid and then coupled by the Lewis acid-promoted glycosidation via the corresponding trichloroacetimidate. Glycosyl phosphorylation and hydrogenolytic deprotection, followed by purification by liquid–liquid partition chromatography, afforded the target compound in 2.9% total yield through 13 steps from N-Troc-d-glucosamine.
Effect of Proline Residue in Polypeptides on the Interactions between Polypeptides and DNA
Authors: Uchida Chieko , Wakamatsu Kaori , Oya Masanao 
Published: June 2006

Abstract
The interaction between high molecular-weight synthetic polypeptides containing proline residue and salmon DNA were studied by circular dichroism spectra (CD) in aqueous solution, 1H NMR in D2O solution, and 13C NMR spectra in solid state. The interactions were compared with those of polypeptides containing lysine residue and DNA. The complexes of poly(Pro) and poly(Pro-co-Gly) with DNA were made by lyophilization after dialysis of the mixed solution of the corresponding solutions. These complexes were soluble in water and insoluble in 1 M NaCl, in contrast to the poly(Lys)–DNA complex, which was insoluble in water and soluble in 1 M (mol dm−3) NaCl. The polypeptides containing proline residue (poly(Pro-co-X)) interacted with DNA in the solution, which differed from the interaction of poly(Lys) with DNA. In addition, the interactions of poly(Pro) and poly(Pro-co-Gly) with DNA differed from each other.
Thermodynamic and Structural Aspects on Solvation Steric Effect in Nonaqueous Solution
Authors: Ishiguro Shin-ichi 
Published: June 2006

Abstract
Formation thermodynamics and structure of halogeno and pseudo-halogeno complexes of transition metal(II) and lanthanide(III) ions have been studied in N,N-dimethylacetamide (DMA) and hexamethylphosphoric triamide (HMPA), and compared with those in N,N-dimethylformamide (DMF). Significant differences in the formation thermodynamics and structure among solvents has been explained in terms of a solvation steric effect. A structural survey by EXAFS demonstrates that solvent coordination number of a solvate metal ion is kept unchanged (weak solvation steric effect) or reduced (strong solvation steric effect) when the metal ion is transferred to DMA or HMPA, respectively, from DMF. DMA usually exhibits a weak solvation steric effect. It elucidates that a weak solvation steric effect of DMA is ascribable mainly to a distortion of the M–O–C–N dihedral angle. The solvent effect operates for a complex with a coordination number larger than four in DMF, but it does not for a complex of four-coordination. Lanthanide(III) ions exhibit a specific solvation steric effect, and an outer-sphere bromo complex in DMF changes to an inner-sphere complex in DMA. Besides, the solvent coordination number varies with solvent composition in DMF–DMA mixtures, and the variation manner strongly depends on the metal ion or the ionic radius. HMPA shows a strong solvation steric effect, and halogeno complexation is significantly enhanced in HMPA relative to that in DMF, although HMPA has a stronger electron-pair donating ability. The coordination number is four or five, and the M–O(HMPA) bondlength is significantly shortened.