Spectra and structure of some transition metal poly(1-pyrazolyl) borates

Jesson, J. P.; Trofimenko, Swiatoslaw; Eaton, D. R.

doi:10.1021/ja00989a014

Cited by 147 publications

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“…This represents the first binary zinc pyrazolate structure determination. Related poly(1-pyrazo1ate)borate zinc complexes were first reported by Trofimenko et al some time ago (3). More recently, zinc and boron centres were featured in a number of polynuclear pyrazolyl bridged spiro species (4) and a variety of pyrazolyl gallate ligands have been used to complex divalent zinc ions (5-7).…”

Section: Introductionmentioning

confidence: 99%

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn₂(dmpz)₄(Hdmpz)₂]

Ehlert¹,

Rettig²,

Storr³

et al. 1990

Can. J. Chem.

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Section: Introductionmentioning

confidence: 99%

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn₂(dmpz)₄(Hdmpz)₂]

Ehlert¹,

Rettig²,

Storr³

et al. 1990

Can. J. Chem.

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“…[I]. On the other hand, the other physical properties (27) of this complex show that it is a typical, almost octahedral, non-labile, Co(I1) complex so that the structure of its second coordination sphere should not be greatly dissimilar from that of other stable complexes of Co(I1) and neighboring transition metal ions. The magnetic anisotropy merely serves as a convenient probe to locate surrounding molecules.…”

Section: Introductionmentioning

confidence: 99%

Structure of the second coordination sphere of transition metal complexes. I. Co(II) complexes with aniline and pyridine

Eaton¹

1969

Can. J. Chem.

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Geometric and thermodynamic parameters relating to the structure of labile second sphere coordination complexes formed between Co(I1) chelates and aniline and pyridine molecules in carbon tetrachloride solution have been obtained. The effect of dipolar interactions, resulting from the magnetic anisotropy of the cobalt chelate, on the nuclear magnetic resonance spectra of the complexing molecules has been utilized for this purpose. Both aniline and pyridine show a preferred direction of approach perpendicular to the three fold symmetry axis of the cobalt compound used. In both cases the preferred intermolecular separation corresponds closely to that expected for a second coordination sphere ligand. The preferred orientation of the aniline molecule places the amino group adjacent to the cobalt complex and the pyridine is oriented with the y hydrogen closest to the chelate. Enthalpy changes of -2.4 +_ 0.2 kcal and -2.9 f 0.3 kcal have been obtained for the formation of the aniline and pyridine complexes, respectively. The effect of averaging tumbling and translational motions on the dipolar shifts has been considered. The meaning of the parameters derived is discussed in the light of the very labile nature of the second coordination sphere complexes. The relevance of these results to the mechanisms of ligand substitution processes and homogeneous catalysis is emphasized.

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“…The extracted species were proved to be MA2 type from slope analysis. It has been reported that the divalent metal chelates which precipitate from aqueous solution of H2B(pz)2-are also MA2 type and that the configuration about the metal is square-planar for Ni(II) and Cu(II) and tetrahedral for Mn(II), Fe(II), Co(lI) and Zn(Il) [1,4,12]. The pH 112 values of H2B(pz)(3,5-dmpz)-and H2B(3,5-dmpz)2-are higher than those of H2B(pz)2, which is mainly attributable to the increase in pKa of the ligands.…”

Section: Methodsmentioning

confidence: 99%

“…It was ascertained that the extracted species are MA2 type. Their chelates should have an octahedral structure except the Cu(H) chelates [ 1,5,12]. Since the two hydrotris-or tetrakis(1-pyrazolyl)borate ligands adopt a mutually staggered configuration (Fig.…”

Section: Methodsmentioning

confidence: 99%

Complex Formation Reaction of Polypyrazolylborates with Divalent Metal Ions in Aqueous Solution Studied by Solvent Extraction Technique

et al. 1991

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-Extraction behavior of divalent transition and group IIA metals with five polypyrazolylborates, H4_nB(pz*)n-(pz: 1-pyrazolyl or 3,5-dimethyl-l-pyrazolyl; n = 2, 3 and 4) has been studied. Bidentate bispyrazolylborate ligands extract divalent transition metals but do not group IIA metals. The selectivity of dihydrobis(1-pyrazolyl)borate for transition metals resembles that of 8-hydroxyquinoline. Methyl substituents in the pyrazole ring increase the stability of chelates through inductive effect and decrease that for small metal ions through steric hindrance. Hydrotris-and tetrakis(1-pyrazolyl)borate, which can act as a tridentate ligand, are highly strong extracting ligands for divalent transition metals. Moreover, these ligands extract Be(II), Mg(II) and Ca(II). Steric characteristics of the ligands contribute to anomalously high stability of the chelates and selectivity for the metal ions.Key wards polypyrazolylborates, transition metal, group IIA metal, liquid-liquid extractionThe poly(1-pyrazolyl)borates, which were first reported by Trofimenko[1], are unique uninegative ligands of the general formula, H4_nB(pz)n-(pz: 1-pyrazolyl; n = 2, 3 and 4), and a wide variety of their chelates of various elements continues to provide a fascinating and fertile field of research to inorganic chemists [2,3]. Dihydrobis(1-pyrazolyl)-borate anion, which is a bidentate ligand, is similar to a fi-diketonate anion and forms bis neutral chelates with divalent transition metal ions. The bispyrazolylborate chelates are different from f3-diketonates in that the chelate ring has a boat type configuration and the metal ion is screened by the ligand moiety (Fig, 1)[4]. Further replacement of the remaining boron hydrogen atoms by pyrazole groups to produce hydrotris-and tetrakis(l-pyrazolyl)borate anion, which can act as a tridentate ligand. They react readily with not only divalent transition metals but also group IIA metals and form stable octahedral chelates (Fig. 2)[5]. The polypyrazolylborates seem very attractive to analytical chemists from a view point of ligand design, because they have unique structures and their electronic and steric parameters can be altered by a proper choice of substituents. However, studies have scarcely been reported on analytical chemistry and chelate chemistry in solution using these ligands. We report here the solvent extraction of divalent metal ions with five polypyrazolylborate ligands in order to clarify the characteristics of the ligands for selective extraction of metais [6][7][8]. EXPERIMENTALReagents and apparatus Dihydrobis(1-pyrazolyl)borate (H2B(pz)z-), hydrotris(1-pyrazolyl)borate (HB(pz)3-), tetrakis(1-pyrazolyl)borate (B(pz)4) and dihydrobis(3,5-dimethyl-l-pyrazolyl)borate (H2B(3,5-dmpz)2-) were synthesized according to Trofimenko's method [1], and dihydro(1-pyrazolyl)(3,5-dimethyl-l-pyrazolyl)borate (H2B(pz)(3,5-dmpz)-) was synthesized according to Frauendorfer s method [9]. These ligands were recrystallized as potassium salts except that H2B(pz)(3,5-dmpz)-was recrystallized ...

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Spectra and structure of some transition metal poly(1-pyrazolyl) borates

Cited by 147 publications

References 0 publications

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn₂(dmpz)₄(Hdmpz)₂]

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn₂(dmpz)₄(Hdmpz)₂]

Structure of the second coordination sphere of transition metal complexes. I. Co(II) complexes with aniline and pyridine

Complex Formation Reaction of Polypyrazolylborates with Divalent Metal Ions in Aqueous Solution Studied by Solvent Extraction Technique

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Spectra and structure of some transition metal poly(1-pyrazolyl) borates

Cited by 147 publications

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Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn2(dmpz)4(Hdmpz)2]

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn2(dmpz)4(Hdmpz)2]

Structure of the second coordination sphere of transition metal complexes. I. Co(II) complexes with aniline and pyridine

Complex Formation Reaction of Polypyrazolylborates with Divalent Metal Ions in Aqueous Solution Studied by Solvent Extraction Technique

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Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn₂(dmpz)₄(Hdmpz)₂]

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn₂(dmpz)₄(Hdmpz)₂]