Structural characteristics of dibromoborylated benzene derivatives

Abstract

The crystal structures of five dibromobenzene derivatives, namely dibromoborylbenzene, C(6)H(5)BBr(2), (I), 1-dibromoboryl-4-(trimethylsilyl)benzene, C(9)H(13)BBr(2)Si, (II), 4-bromo-1-(dibromoboryl)benzene, C(6)H(4)BBr(3), (III), dibromo(dimethylamino)(phenyl)borane, C(8)H(12)BBr(2)N, (IV), and dibromo(dimethylsulfanyl)[4-(trimethylsilyl)phenyl]borane, C(11)H(19)BBr(2)SSi, (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 -BBr(2) 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 -BBr(2) group tends to be coplanar with the aromatic ring to which it is attached.

Synthesis and characterisation of the complete series of B–N analogues of triptycene

“…Combustion analyses were performed by the Microanalytical Laboratory of the Goethe University Frankfurt; HRMS measurements were performed on a MALDI LTQ Orbitrap spectrometer (Thermo Scientific). The compounds Li 2 [7]•OEt 2 , 23 44 4-iodopyrazole, 45 nBu 3 SnCuCtBu, 46 4-(trimethylsilyl)pyrazole, 47 and 3,5-di(tert-butyl)pyrazole 48 are literature known; the amount of OEt 2 present in the samples of Li 2 [1,1′-fc(BH 3 ) 2 ]•(OEt 2 ) 0.25 after prolonged storage in a screwcapped vial in the glove-box was determined by 1 H NMR spectroscopy.…”