THE RATES OF EXCHANGE OF WATER MOLECULES FROM AL(III)-METHYLMALONATE COMPLEXES: THE EFFECT OF CHELATE RING SIZE - ACIDITY CONSTANTS OF SILICIC ACID AND THE IONIC PRODUCT OF WATER IN THE MEDIUM RANGE 0.5-2.0 M NA(CL) AT 25 C
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dc.contributor.author | Casey W.H. | |
dc.contributor.author | Phillips B.L. | |
dc.contributor.author | Nordin J.P. | |
dc.contributor.author | Sullivan D.J. | |
dc.date.accessioned | 2020-12-29T10:10:02Z | |
dc.date.available | 2020-12-29T10:10:02Z | |
dc.date.issued | 1998 | |
dc.identifier | https://elibrary.ru/item.asp?id=86569 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 1998, , 16, 2789-2797 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/21652 | |
dc.description.abstract | Rate coefficients are reported for exchange of hydration waters in the inner-coordination-sphere of Al(III)-methylmalonate complexes with bulk solution as determined via 17O-NMR. Surprisingly, water molecules in the thermodynamically less-stable complexes containing six-membered chelates are much more labile than those in five-membered oxalate-Al(III) complexes. The rate parameters for the Al(mMal)+ complex are: kex298=6.6.102 s-1,ΔH#=66(+/-1) kJ mol-1;ΔS#=30.6(+/-2) J mol-1 K-1 and for the Al(mMal)2- complex are kex298=6.9.103 s-1,ΔH#=55(+/-3) kJ mol-1;ΔS#=12.8(+/-11) J mol-1 K-1 The surprising trend in reactivity is attributable either to differences in the Lewis basicities of oxygens in bidentate oxalate and methylmalonate ligands, or to rapid dissociation/reassociation of one of the acetate groups to the metal center. These results identify a useful case where trends in the apparent labilities of dissolved and presumed surface complexes deviate sharply. This deviation could be usefully exploited to probe surfaces if ligand-promoted dissolution rates could be compared at conditions where inner-sphere and outer-sphere chelate complexes could be distinguished spectroscopically. We expect inner-sphere oxalate to have a smaller labilizing effect than malonate or methylmalonate. A contrary result would indicate structural dissimilarity between complexes on the surface and in solution, or perhaps steric hindrance. | |
dc.title | THE RATES OF EXCHANGE OF WATER MOLECULES FROM AL(III)-METHYLMALONATE COMPLEXES: THE EFFECT OF CHELATE RING SIZE - ACIDITY CONSTANTS OF SILICIC ACID AND THE IONIC PRODUCT OF WATER IN THE MEDIUM RANGE 0.5-2.0 M NA(CL) AT 25 C | |
dc.type | Статья |
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