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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Kinetic iron stable isotope fractionation between iron (-II) and (-III) complexes in solution
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Kinetic iron stable isotope fractionation between iron (-II) and (-III) complexes in solution

机译：溶液中铁（-II）和（-III）配合物之间的动力学铁稳定同位素分馏

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摘要

Iron stable isotope fractionation between tris(2,2'-bipyridine) iron-II ([Fe~(II)(bipy)_3]~(2+)) and iron-III chloride complexes has been measured using plasma source mass spectrometry. The experimental protocol involves complexing Fe~(II) ion with 2,2'-bipyridine in a Fe~(II)/Fe~(III) chloride solution and then separating the Fe~(II) and Fe~(III) solution species in 6 M HCl on an anion exchange resin. Large isotopic variations of ε~(57)Fe and ε~(56)Fe are experimentally measured in the two separated solution fractions, with isotopic fractionations increasing from Δ(Fe~(II)-Fe~(III)) = 25 to 174 ε units for ~(57)Fe/~(54)Fe and 17 to 117 ε units for ~(56)Fe/~(54)Fe. The increase in fractionations correlates with a decrease in the mole fraction of Fe~(II) in the solution (Fe~* = (Fe~(II))/[(Fe~(II)) + (Fe~(III))]) that results from the dissociation and breakdown of [Fe~(II)(bipy)_3]~(2+) complex in 6 M HCl solution. The data variations are mainly ascribed to a kinetic fractionation occurring during this dissociation reaction. Mass balance calculations, assuming that a Rayleigh law describes the overall isotopic trends, suggest a kinetic fractionation of ca. 1.010 (～100 ε units). The magnitude of this fractionation is attributed to the rupturing of the strong covalent bonds between 2,2'-bipyridine and Fe~(II) ion. The experimental data confirm that the coordination chemistry of iron exhibits a profound control on its isotopic behaviour and that kinetic fractionations may play an important role in its isotope geochemistry, as was also found in the pioneering experimental studies of the sulphur isotopic system is solution.
机译：已经使用等离子体源质谱法测量了三（2,2'-联吡啶）铁-II（[Fe〜（II）（bipy）_3]〜（2+））和铁-III氯化物络合物之间的铁稳定同位素分馏。实验方案涉及在Fe〜（II）/ Fe〜（III）氯化物溶液中将Fe〜（II）离子与2,2'-联吡啶络合，然后分离Fe〜（II）和Fe〜（III）溶液种类在阴离子交换树脂上的6 M HCl中溶解。实验测量了两个分离的溶液馏分中ε〜（57）Fe和ε〜（56）Fe的大同位素变化，同位素分馏从Δ（Fe〜（II）-Fe〜（III））= 25增至174 〜（57）Fe /〜（54）Fe的ε单位和〜（56）Fe /〜（54）Fe的17到117ε单位。分馏的增加与溶液中Fe〜（II）的摩尔分数的降低有关（Fe〜* =（Fe〜（II））/ [（Fe〜（II））+（Fe〜（III）） ]）是[Fe〜（II）（bipy）_3]〜（2+）络合物在6 M HCl溶液中的解离和分解所致。数据变化主要归因于在该离解反应期间发生的动力学分级分离。假设瑞利定律描述了整个同位素趋势，则质量平衡计算表明，约有动力学分数。 1.010（〜100ε单位）。该分级的大小归因于2，2'-联吡啶和Fe〜（II）离子之间的强共价键的断裂。实验数据证实，铁的配位化学对其同位素行为表现出深远的控制，动力学分级分离可能在其同位素地球化学中起重要作用，硫磺同位素系统的开创性实验研究也发现溶液是铁。

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