Determination of rates of optical inversion of aluminum .beta.-diketonate complexes by nuclear magnetic resonance studies of racemic mixtures

Fortman, John J.; Sievers, Robert E.

doi:10.1021/ic50057a020

Cited by 40 publications

(12 citation statements)

References 1 publication

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“…There is also a *H NMR evidence that inversion and diketonate R group exchange in Ti-(R/COCHCOR,)2(OR)2 proceed by a twist mechanism.39 Some support for this proposal, but not a tangible one, might be obtained from the low preexponential factors and negative activation entropies in Table VII. 40 Non-bond-rupture mechanisms for cis «=t trans isomerization of octahedral M(A-B)3 is usually thought to involve a rhombic twist (Scheme II, top). Perhaps this is more assumed than proven.…”

Section: Resultsmentioning

confidence: 99%

Trigonal versus nontrigonal deformation from octahedral geometry in d0 metal six-coordination: two geometrical isomers of [metal tris(norbornane-exo-2,3-dithiolate)]- (metal = niobium, tantalum) and their interconversion

Tatsumi¹,

Matsubara²,

Inoue³

et al. 1989

J. Am. Chem. Soc.

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The tris(norbornane-exo-2,3-dithiolate) complexes of Nbv and Tav, [A][M(ndt)3] (A = Ph4P+, Et4N+, n-Bu4N+), have been synthesized and fully characterized. These tris-chelate complexes can have two unique geometrical forms, synclastic and anticlastic, due to the unsymmetric nature of the ndt ligand in the direction perpendicular to the MS2 coordination plane, and existence of such isomers has been established by the X-ray derived structures of [Ph4P][Ta(ndt)3] (2a) (synclastic) and

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Section: Resultsmentioning

confidence: 99%

Trigonal versus nontrigonal deformation from octahedral geometry in d0 metal six-coordination: two geometrical isomers of [metal tris(norbornane-exo-2,3-dithiolate)]- (metal = niobium, tantalum) and their interconversion

Tatsumi¹,

Matsubara²,

Inoue³

et al. 1989

J. Am. Chem. Soc.

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“…For a model The above conclusion has important consequences in the area of intramolecular rearrangements of Al-(111) p diketonates (3). A number of authors (14)(15)(16) have discussed such mechanisms in detail but have been unable to reach a definite decision a s to whether they involve a bond rupture or a twisting process. The above result eliminates all bond rupture mechanisms.…”

Section: 'Fastmentioning

confidence: 99%

The reactions of metal acetylacetonates with acids

Nixon¹,

Eaton²

1978

Can. J. Chem.

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The reactions of a number of nietal acetylacetonates with trifluoroacetic acid have been investigated using nnir. The initial reaction involves protonation o n the carbon atom of the ligand. In the case of the aluminum compound in coordinating solvents there is further reaction t o give cationic complexes. T h e results are used t o reinterpret the kinetics of ligand exchange for this compound. It is argued that, contrary to previous suggestions, the slow step is the breaking of the first nietal oxygen bond to form a dangling ligand intermediate. A consequence of this conclusion is that intramolecular rearrangements of Al(111) p diketonates must proceed by twisting rather than by bond rupture mechanisms.A. J. C. NIXON et D. R. EATON. Can. J. Chem. 56, 1928(1978.Faisant appel a la rnin, on a etudie les reactions d'un certain nonibre d'acetylacetonates de metaux avec I'acide trifluoroacetique. La reaction initiale iniplique la protonation de I'atonie cle carbone du ligand. Dans le cas du compose d e I'aluniiniuni, dans des solvants permettant la coordination, il y a une reaction subsequente conduisant a des complexes cationiques. O n a utilise ces resultats pour reinterpreter la cinetique d e I'echange d e ligand d e ce c o~n p o s t .On presente des arguments qui, contrairernent aux suggestions anterieures, suggereraient quc I'etape deterniinante correspond aux bris du premier lien metal oxygene pour former un intermediaire coniportant un ligand en suspens. Une consequence de cette conclusion implique que les rearrangements intranioltculaires d e p-dicetonates de AI(1II) doivent proceder p a r dcs torsions plutBt que par un mecanisme de rupture des liaisons.[Traduit par le journal]

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“…ß-diketonate exchange on other metal atoms. [21][22][23][24][25][26][27][28]31 In order to assess the relative importance of enthalpy and entropy contributions to the nonstatistical equilibria, we have measured the temperature dependence of the equilibrium constant for the reaction Ti(bztf)2F2 + Ti(dpm)2F2 <4 2Ti(bztf)(dpm)F2. Among the reactions which exchange ligands that differ by one CF3 group, this is the reaction which exhibits the greatest deviation from random scrambling.…”

Section: Table III Equilibriummentioning

confidence: 99%

Proton magnetic resonance studies of ligand-exchange equilibriums for dihalo- and diethoxybis(.beta.-diketonato)titanium(IV) complexes

Fay¹,

Lowry²

1974

Inorg. Chem.

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Determination of rates of optical inversion of aluminum .beta.-diketonate complexes by nuclear magnetic resonance studies of racemic mixtures

Cited by 40 publications

References 1 publication

Trigonal versus nontrigonal deformation from octahedral geometry in d0 metal six-coordination: two geometrical isomers of [metal tris(norbornane-exo-2,3-dithiolate)]- (metal = niobium, tantalum) and their interconversion

Trigonal versus nontrigonal deformation from octahedral geometry in d0 metal six-coordination: two geometrical isomers of [metal tris(norbornane-exo-2,3-dithiolate)]- (metal = niobium, tantalum) and their interconversion

The reactions of metal acetylacetonates with acids

Proton magnetic resonance studies of ligand-exchange equilibriums for dihalo- and diethoxybis(.beta.-diketonato)titanium(IV) complexes

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