The First Boroselenates as new Silicate Analogues. Issue 1 (30th October 2014)

• Record Type: Journal Article
• Authors: Daub, Michael; Hillebrecht, Harald
• Is Part Of: Chemistry. Volume 21:Issue 1(2015)
• Page Start: 298
• Page End: 304
• Publication Date: 2014-10-30
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201404100
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The first boroselenates were obtained as single crystals by the reaction of selenic acid with boron acid and the corresponding alkali carbonates. The structure determinations showed a far‐reaching analogy to very recently described borosulfates and the borophosphates, that is, tetrahedral BO<sub>4</sub> and SeO<sub>4</sub> units linked by common corners. In each case, the BO<sub>4</sub> tetrahedra are surrounded by SeO<sub>4</sub> tetrahedra. As a function of the B/Se ratio, this results in chains (1:3; Cs<sub>3</sub>[B(SeO<sub>4</sub>)<sub>3</sub>], Rb<sub>3</sub>[B(SeO<sub>4</sub>)<sub>3</sub>]), isolated pentamers (1:4; HK<sub>4</sub>[(B(SeO<sub>4</sub>)<sub>4</sub>]), or pentamers with additional isolated SeO<sub>4</sub> tetrahedra (1:5; (H<sub>3</sub>O)Na<sub>6</sub>[B(SeO<sub>4</sub>)<sub>4</sub>](SeO<sub>4</sub>). Compound Rb<sub>3</sub>[B(SeO<sub>4</sub>)<sub>3</sub>] (orthorhombic, <italic>Ibca</italic>, <italic>Z</italic>=8, <italic>a</italic>=7.508(2), <italic>b</italic>=15.249(3), <italic>c</italic>=23.454(5) Å) is isotypic to Rb<sub>3</sub>[B(SO<sub>4</sub>)<sub>3</sub>]) and Ba<sub>3</sub>[B(PO<sub>4</sub>)<sub>3</sub>]. Compound Cs<sub>3</sub>[B(SeO<sub>4</sub>)<sub>3</sub>] (monoclinic, <italic>P</italic>2<sub>1</sub>/<italic>c</italic>, <italic>Z</italic>=4, <italic>a</italic>=11.3552(4), <italic>b</italic>=7.9893(3), <italic>c</italic>=15.7692(6) Å, <italic>β</italic>=101.013(1)°) represents a distorted variant of Rb<sub>3</sub>[B(SeO<sub>4</sub>)<sub>3</sub>]. The isolated pentamers in HK<sub>4</sub>[(B(SeO<sub>4</sub>)<sub>4</sub>]) (triclinic, <italic>P</italic><inline-formula><alternatives><tex-math notation="tex"><![CDATA[$\bar 1$]]></tex-math><inline-graphic xlink:href="ark:/27927/pgh2xpv1b9b" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></alternatives></inline-formula>, <italic>Z</italic>=6, <italic>a</italic>=7.5303(1), <italic>b</italic>=7.5380(1), <italic>c</italic>=42.3659(4) Å, <italic>α</italic>=88.740(1), <italic>β</italic>=89.971(1), <italic>γ</italic>=89.971(1)°) were also found in K<sub>5</sub>[(B(SO<sub>4</sub>)<sub>4</sub>] and Na<sub>5</sub>[(B(SO<sub>4</sub>)<sub>4</sub>]. Compound (H<sub>3</sub>O)Na<sub>6</sub>[B(SeO<sub>4</sub>)<sub>4</sub>](SeO<sub>4</sub>) (tetragonal, <italic>I</italic><inline-formula><alternatives><tex-math notation="tex"><![CDATA[$\bar 4$]]></tex-math><inline-graphic xlink:href="ark:/27927/pgh2xpv19z9" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></alternatives></inline-formula>, <italic>a</italic>=9.9796(1), <italic>c</italic>=18.2614(2) Å) is a super structure of the borophosphates Sr<sub>6</sub>[B(PO<sub>4</sub>)<sub>4</sub>](PO<sub>4</sub>) and Pb<sub>6</sub>[B(PO<sub>4</sub>)<sub>4</sub>](PO<sub>4</sub>). Because the tetrahedra are only connected through apices, there are topological analogies to silicates. Therefore, boroselenates may have a similar variability of crystal structures, such as borosulfates and borophosphates.</p> </abstract>