Structural characteristics of dibromo­borylated benzene derivatives

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.