Alkaline earth cryptates: dynamics and stabilities in different solvents

Cox, Brian G.; Truong, Ng. van; Schneider, Hermann

doi:10.1021/ja00317a017

Cited by 36 publications

(7 citation statements)

References 10 publications

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“…Ion binding to calcium signaling proteins 265 constant increases 100-fold as the ionic radius grows from Ca 2+ to Ba 2+ (Cox et al 1984). Dramatic effects are also seen for ions of different charge.…”

Section: Principles Of Kinetic Tuning Illustrated By Chelatorsmentioning

confidence: 99%

Molecular Tuning of Ion Binding to Calcium Signaling Proteins

Falke¹,

Drake²,

Hazard³

et al. 1994

Quart. Rev. Biophys.

359

407

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Section: Principles Of Kinetic Tuning Illustrated By Chelatorsmentioning

confidence: 99%

Molecular Tuning of Ion Binding to Calcium Signaling Proteins

Falke¹,

Drake²,

Hazard³

et al. 1994

Quart. Rev. Biophys.

359

407

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“…A striking difference between the monensin complexes and those of the neutral cryptand [e.g. (2,2,37] and the crown ether (e.g. dibenzo-I 8-C-638) ligands is the variation in stability constants on transfer from the protic solvents, MeOH and EtOH, to the aprotic solvents.…”

mentioning

confidence: 99%

Stability constants of complexes of monensin and lasalocid with alkali-metal and alkaline-earth-metal ions in protic and polar aprotic solvents

Cox¹,

Trưởng²,

Rzeszotarska³

et al. 1984

J. Chem. Soc., Faraday Trans. 1

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Measurements have been made of the stability constants of complexes of the anionic ionophores monensin and lasalocid with alkali-metal cations, alkaline-earth-metal cations and Ag+ in several solvents, both protic and polar aprotic. The complexes of monensin are very stable and show a sharp stability maximum among the alkali-metal cations for the Na+ complex in all solvents. Compared with complexes of various neutral ionophores, the stability constants of monensin complexes are relatively much higher in aprotic than protic solvents. This may be attributed to a loss of solvation altering the free energy and conformation of the monensin anion on transfer from protic to aprotic solvents. Complexes of the smaller lasalocid ion are less stable, less sensitive to solvent variation and show a different selectivity pattern to those of monensin. Structural features of the two ligands responsible for the different complexing properties are discussed.

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“…Reaction of RMo(CO)3C5H5 with a number of phosphines and phosphites proceeds rapidly and quantitatively according to reaction 5. This reaction has been widely studied12 RMo(CO)3C5H5 + PR3 -RC(0)Mo(CO)2(PR3)C5H5 (5) as have analogous reactions of RMn(CO)5,13 RCo(CO)4,14 and a number of other alkylmetal carbonyls. Ligand-induced carbonyl insertion is best viewed thermodynamically (but not mechanistically) as occurring in two steps, phosphine substitution and carbonyl insertion: RMo(CO)3C5H5 + PR3 -RMo(CO)2(PR3)C5Hj + CO (6) RMo(CO)2(PR3)C5H5 + CO -* RC(0)Mo(CO)2(PR3)C5H5 (7) The enthalpy of eq 6 reflects the difference in the Mo-CO and Mo-PR3 bond strengths.…”

Section: Resultsmentioning

confidence: 99%

Heats of reaction of RMo(CO)3C5H5 (R = H, Me, Et) with phosphines and phosphites: thermodynamic study of the carbonyl-insertion reaction

et al. 1986

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The heats of reaction of HMo(CO)3C5H5 with a series of phosphines and phosphites, producing HMo(CO)2(PR3)C5H5, have been measured by solution calorimetry. The order of relative Mo-PR3 bond strengths, PMe3 = P-h-Bu3 > P(OMe)3 > PMe2Ph > PMePh2, closely resembles that determined earlier for the complexes/ac-(PR3)3Mo(CO)3. The heats of reaction of RMo(CO)3C5H5 (R = CH3, C2H5), producing the phosphine-substituted acyl complexes RC(0)Mo(CO)2(PR3)C5Hs, were also studied thermochemically. This reaction can be viewed as involving both phosphine substitution and carbonyl insertion. With use of the enthalpy of phosphine substitution of HMo(CO)3C5H5 as a model, the enthalpy of carbonyl insertion is calculated. For both R = CH3 and R = C2FI5 the carbonyl-insertion reaction is favored for more basic phosphines with a difference of about 2 kcal/mol between PMe3 (most favored) and P(OMe)3 (least favored). Carbonyl insertion into the Mo-Et bond is about 3 kcal/mol more favorable than into the Mo-CH3 bond. Attempts to prepare the unsubstituted acyls RC(0)Mo(CO)3C5H5 by carbonylation of the alkyls in THF led to facile reductive elimination of RC(0)C5H5 (35 °C, 1 atm of CO), producing Mo(CO)6. Migration of the acyl group to the coordinated cyclopentadienyl ring in the presence of CO pressure and thermodynamic instability in the absence of CO pressure explain the lack of success in preparing RC(0)Mo(CO)3C5H5 for simple alkyl groups.

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Alkaline earth cryptates: dynamics and stabilities in different solvents

Cited by 36 publications

References 10 publications

Molecular Tuning of Ion Binding to Calcium Signaling Proteins

Molecular Tuning of Ion Binding to Calcium Signaling Proteins

Stability constants of complexes of monensin and lasalocid with alkali-metal and alkaline-earth-metal ions in protic and polar aprotic solvents

Heats of reaction of RMo(CO)3C5H5 (R = H, Me, Et) with phosphines and phosphites: thermodynamic study of the carbonyl-insertion reaction

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