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Date: 21-3-2017
1278
Date: 23-3-2017
1331
Date: 3-1-2017
1412
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Polyselenides and polytellurides
Although Se and Te analogues of polysulfanes do not extend beyond the poorly characterized H2Se2 and H2Te2, the chemistries of polyselenides, polytellurides and their metal complexes are well established. Equations 15.43–1.3 illustrate preparations of salts of [Sex]2- and [Tex]2- ; for details of crown ethers and cryptands.
(1.1)
(1.2)
(1.3)
(1.4)
(1.1) (1.1)
Structurally, the smaller polyselenide and polytelluride ions resemble their polysulfide analogues, e.g. [Te5]2- has structure 1.1 with a helically twisted chain. The structures of higher anions are less simple, e.g. [Te8]2- (1.1) can be considered in terms of [Te4]2- and [Te3]2- ligands bound to a Te2+ centre. Similarly, [Se11]2- can be described in terms of two [Se5]2- ligands chelating to an Se2+centre. The coordination chemistry of the [Sex]2- and [Tex]2- chain anions has developed significantly since 1990; examples include [(Te4)Cu(µ-Te4)Cu)Te4(]4- and [(Se4)2In(µ-Se5)In(Se4)2]4- (both of which have bridging and chelating ligands), octahedral [Pt(Se4)3]2- with chelating [Se4]2- ligands, [Zn(Te3)(Te4)]2- and [Cr(Te4)3]3-.
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"تهديد صامت" قد يزيد من خطر إصابة غير المدخنين بسرطان الرئة
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نجاح أول تجربة تجول لبعثة خاصة بالفضاء في التاريخ
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المجمع العلمي يصدر كتابه الحادي عشر ضمن مشروع سلسلة الرسائل الجامعية القرآنية
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