Multinuclear magnetic resonance studies on aluminium chelates. Part i. Chelates with catechol and disodium 4,5-dihydroxybenzene-1,3-disulfonate

Mhatre, S N; Karweer, S. B.; Pradhan, Padmanava; Iyer, Ramaswamy K.; Moorthy, P.N.

doi:10.1039/dt9940003711

Cited by 8 publications

(4 citation statements)

References 17 publications

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“…In addition, at pH > 9, two complexes, [Al(H - 1 ga) 2 ] - and [Al(H - 1 ga)(OH) 2 ] - , were tentatively assigned as having tetrahedral aluminum, on the basis of chemical shifts of 60.5 and 55.5 ppm, respectively. Chemical shifts in the octahedral and tetrahedral range were also seen in the aluminum−tartrate system and in the aluminum−catechol system . The downfield (tetrahedral) resonances were only observed above pH 9.…”

Section: Discussionmentioning

confidence: 84%

“…Chemical shifts in the octahedral and tetrahedral range were also seen in the aluminum-tartrate system 59 and in the aluminum-catechol system. 60 The downfield (tetrahedral) resonances were only observed above pH 9. While the chemical shift of [Al(bped)(OH)] lies in the range of 5-coordinate aluminum, it should be noted that the vast majority of octahedral aluminum complexes studied by 27 Al NMR have the Al(III) ion coordinated by only oxygen donors or by polyamino polycarboxylates; no shifts of octahedral aluminum complexes containing pyridyl donors have been reported until now.…”

Section: Discussionmentioning

confidence: 97%

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Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

1997

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A new preparation of N,N'-bis(2-pyridylmethyl)ethylenediamine-N,N'-diacetic acid (H(2)bped) is reported, and its properties of complexation with Al(III), Ga(III), In(III), and Co(III) are investigated. The molecular structure of the cobalt(III) complex [Co(bped)]PF(6).CH(3)CN.H(2)O (C(20)H(25)CoF(6)N(5)O(5)P) has been solved by X-ray methods; the complex crystallizes in the triclinic space group P&onemacr;, with a = 10.611(2) Å, b = 12.720(2) Å, c = 9.868(1) Å, alpha = 102.70(1) degrees, beta =93.60(1) degrees, gamma = 106.96(1) degrees, and Z = 2. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.041 (R(w) = 0.038) for 4312 reflections with I > 3sigma(I). The Co(III) ion is coordinated in a distorted octahedral geometry with an N(4)O(2) donor atom set. The carboxylato oxygen atoms are coordinated trans, while the pyridyl nitrogen atoms are coordinated cis. The largest distortion from octahedral geometry is the N(pyridyl)-Co-N(pyridyl) angle of 107 degrees. Complex formation constants have been measured at 25 degrees C (&mgr; = 0.16 M (NaCl)). log K([M(bped)](+)) (log K([M(bped)(OH)])): M = Al, 10.85 (6.37); M = Ga, 19.89 (15.62); M = In, 22.6 (15.44). A protonated complex was also detected, [Ga(Hbped)](2+), log K = 21.79. The order of stability is In(III) > Ga(III) > Al(III) for the binary species, [M(bped)](+). The solution structures of the complexes have been probed in multinuclear NMR ((1)H, (13)C, (27)Al) studies, and these solution structures are compared with the solid state structure of the cobalt(III) complex. The complexes [In(bped)](+) and [In(bped)(OH)] are proposed to contain 7-coordinate In(III) with water and hydroxide completing the respective coordination spheres. The gallium complexes are proposed to be 6-coordinate: the [Ga(Hbped)](2+) complex contains a nondeprotonated carboxylic acid group which is not coordinated, and [Ga(bped)(OH)] contains a coordinated hydroxide which displaces a carboxylato donor. The [Al(bped)(OH)] complex may be 5-coordinate on the basis of its downfield (27)Al NMR chemical shift, 54 ppm.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 97%

Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

1997

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“…The four nitrogen atoms in the basal plane constitute N(1)–Al–N(3) and N(2)–Al–N(4) angles of 153.5° and 156.4°, respectively, which are less obtuse in comparison to [ 1 -thf][PPh 4 ]. This adduct represents a rare example of a dianionic aluminum species − and to the best of our knowledge, the first dianionic p-block metal hydride . Metathesis of the lithium salts of [ 1 -H] 2– with PPh 4 Cl in CH 2 Cl 2 induced precipitation of LiH and LiCl and the formation of naked [ 1 ][PPh 4 ], thus explaining the above-described formation of [ 1 ][PPh 4 ].…”

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confidence: 81%

Calix[4]pyrrole Aluminate: A Planar Tetracoordinate Aluminum(III) Anion and Its Unusual Lewis Acidity

2019

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Tetracoordinate aluminum(III) anions are generally tetrahedral and non-Lewis acidic. Herein, we describe the first planar tetracoordinate aluminum anion. The anion is isolated in its free form, representing a new “anti-van’t Hoff/Le Bel” case. Despite its negative charge, it remains Lewis acidic and permits the formation of various unique adducts, e.g., a dianionic p-block metal hydride. Turning an inert spectator anion into a Lewis acid by planarization verifies theoretical predictions made 40 years ago, ultimately connects “anti-van’t Hoff/Le Bel” structure with reactivity, and pushes further the field of geometrically enhanced p-block element reactivity.

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“…Numerous potentiometric and NMR studies have addressed the problem of aqueous Al 3+ speciation and Al 3+ −organic complexation. − Most of these studies observed broad shoulders forming next to the Al 3+ (aq) peak at 0 ppm with formation of Al 3+ −carboxylate complexes. Commonly, these peaks in the 0−20 ppm chemical shift range are assigned to bi- and tridentate complexes whenever there are two or more O-bearing functional groups within the acid molecule.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Calculation of Aqueous Aluminum and Aluminum−Carboxylate Complex Energetics and ²⁷Al NMR Chemical Shifts

1999

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Al3+ hydrolysis in aqueous solution was modeled with ab initio calculations. Structural changes surrounding the cation as protons are removed from the initial Al3+(H2O)6 molecular cluster were predicted. A correlation of the model energy changes and experimental equilibrium constants for these reactions was also found. Calculations of the 27Al NMR chemical shift between the species Al3+(H2O)6 and [Al(OH)4]- were performed to test the feasibility of predicting 27Al NMR chemical shifts in aqueous solution with gas-phase molecular orbital calculations on small clusters. Energetics of Al3+−carboxylic acid complex formation in solution were also calculated using the self-consistent isodensity polarized continuum model (SCIPCM) to account for long-range solvation effects. Comparisons of calculated 27Al NMR chemical shifts in model Al3+−carboxylate complexes to experimentally assigned values were made to test this methodology and previous peak assignments in 27Al NMR spectra of Al3+−carboxylic acid solutions. Results suggest that NMR peaks observed in acidic solutions of carboxylic acids should be re-interpreted in terms of monodentate or protonated bidentate species. Peaks observed as solution pH increases are likely due to formation of aluminum oligomers complexing with ligands and not bidentate complexes with isolated Al3+ cations as previously interpreted.

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Multinuclear magnetic resonance studies on aluminium chelates. Part i. Chelates with catechol and disodium 4,5-dihydroxybenzene-1,3-disulfonate

Cited by 8 publications

References 17 publications

Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

Calix[4]pyrrole Aluminate: A Planar Tetracoordinate Aluminum(III) Anion and Its Unusual Lewis Acidity

Ab Initio Calculation of Aqueous Aluminum and Aluminum−Carboxylate Complex Energetics and ²⁷Al NMR Chemical Shifts

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Multinuclear magnetic resonance studies on aluminium chelates. Part i. Chelates with catechol and disodium 4,5-dihydroxybenzene-1,3-disulfonate

Cited by 8 publications

References 17 publications

Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

Calix[4]pyrrole Aluminate: A Planar Tetracoordinate Aluminum(III) Anion and Its Unusual Lewis Acidity

Ab Initio Calculation of Aqueous Aluminum and Aluminum−Carboxylate Complex Energetics and 27Al NMR Chemical Shifts

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Ab Initio Calculation of Aqueous Aluminum and Aluminum−Carboxylate Complex Energetics and ²⁷Al NMR Chemical Shifts