Read More
Date: 12-1-2017
1052
Date: 17-11-2020
2547
Date: 24-1-2018
1284
|
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-.
|
|
15 نوعا من الأطعمة تساعدك على ترطيب جسمك خلال موجة الحر
|
|
|
|
|
دول عربية تقرر قطع الكهرباء لساعات محددة يوميا بسبب الحرارة
|
|
|
|
|
بالصور: بمناسبة عيد الغدير الاغر.. قراءة خطبة النبي الأكرم (ص وآله) بالمسلمين في يوم (غدير خم)
|
|
|