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Mol­ecules of the title compound [systematic name: 2,4,6-(penta­fluorophenyl)-1,3,5,2,4,6-trioxatriborinane], C18B3F15O3, are located on crystallographic twofold rotation axes which run through the boroxine and one of the penta­fluoro­phenyl rings. The boroxine ring (r.m.s. deviation = 0.027 Å) and the penta­fluoro­phenyl rings (r.m.s. deviations = 0.004 and 0.001 Å) are essentially planar. The dihedral angles between the boroxine and the two symmetry-independent benzene rings are 8.64 (10) and 8.74 (12)°. The two benzene rings are mutually coparallel [dihedral angle = 0.80 (11)°]. The packing shows planes of mol­ecules parallel to (\overline{2}01), with an inter­planar spacing of 2.99 Å. Within these planes, all the mol­ecules are oriented in the same direction, whereas in neighbouring planes the direction is inverted. Short B...F contacts of 3.040 (2) and 3.1624 (12) Å occur between planes. The geometric parameters of the boroxine ring in the title compound agree well with those of comparable boroxine structures, while the packing reveals some striking similarities and differences.

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The crystal structures of five dibromo­benzene derivatives, namely dibromo­boryl­benzene, C6H5BBr2, (I), 1-dibromo­bor­yl-4-(trimethyl­silyl)­benzene, C9H13BBr2Si, (II), 4-bromo-1-(di­bromo­boryl)­benzene, C6H4BBr3, (III), dibromo(di­methyl­am­ino)­(phenyl)­borane, C8H12BBr2N, (IV), and dibromo­(di­methyl­sulfanyl)­[4-(trimethyl­silyl)­phenyl]­borane, C11H19BBr2SSi, (V), have been determined. Compounds (I)-(IV) crystallize with one mol­ecule in the asymmetric unit, but the mol­ecule of (V) is located on a crystallographic mirror plane, implying twofold disorder of the central aromatic ring, the S atom and one of the methyl groups bonded to the S atom. In (I), (II) and (III), the B atom is three-coordinated, and in (IV) and (V) it is four-coordinated. The geometric parameters of the -BBr2 group in these five structures agree well with those of comparable structures retrieved from the Cambridge Structural Database. The C-B and B-Br bond lengths in the mol­ecules with a three-coordinated B atom are significantly shorter than those in the mol­ecules with a four-coordinated B atom. In the compounds with a three-coordinated B atom, the -BBr2 group tends to be coplanar with the aromatic ring to which it is attached.
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