Structural characteristics of dibromoborylated benzene derivatives.

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.

Copper complexes of mono- and ditopic [(methylthio)methyl]borates: missing links and linked systems en route to copper enzyme models.

TMEDA-free (TMEDA: tetramethylethylenediamine) LiCH(2)SMe is a suitable reagent for the selective introduction of (methylthio)methyl groups into PhBBr(2) and its p-silylated derivative Me(3)Si--C(6)H(4)--BBr(2). The resulting compounds, R*--C(6)H(4)--B(Br)(CH(2)SMe) (R*=H: 2; R*=SiMe(3): 7) and PhB(CH(2)SMe)(2) (3), form cyclic dimers through B--S adduct bonds in solution and in the solid state. Compounds 2 and 3 have successfully been used for preparing the (N(2)S) scorpionate [PhBpz(2)(CH(2)SMe)](-) ([5](-)) (pz: pyrazol-1-yl) and the (NS(2)) scorpionate [PhBpz(CH(2)SMe)(2)](-), respectively. Compound 7 proved to be an excellent building block for the heteroditopic poly(pyrazol-1-yl)borate p-[pz(3)B--C(6)H(4)--Bpz(2)(CH(2)SMe)](2-) ([10](2-)) that mimics the two ligation sites of the copper enzymes peptidylglycine alpha-hydroxylating monooxygenase and dopamine beta-monooxygenase. Treatment of the monotopic tripod [5](-) with CuCl and CuBr(2) results in the formation of complexes K[Cu(5)(2)] and [Cu(5)(2)]. An X-ray crystallography study of K[Cu(5)(2)] revealed a tetrahedral (N(2)S(2)) coordination environment for the Cu(I) ion, whereas the Cu(II) ion of [Cu(5)(2)] possesses a square-pyramidal (N(4)S) ligand sphere (S-atom in the axial position). The remarkable redox properties of K[Cu(5)(2)] and [Cu(5)(2)] have been assessed by cyclic voltammetry and quantum chemical calculations. The reaction of K[Cu(5)(2)] with dry air leads to the Cu(II) species [Cu(5)(2)] and to a tetranuclear Cu(II) complex featuring [PhB(O)pz(2)](2-) ligands. Addition of CuCl to K(2)[10] gives the complex K(3)[Cu(10)(2)] containing two ligand molecules per Cu(I) center. The Cu(I) ion binds to both heteroscorpionate moieties and thereby establishes a coordination environment similar to that of the Cu(I) ion in K[Cu(5)(2)].

µ-Hydroxido-bis-[(2,2'-bipyridine)tricarbonyl-rhenium(I)] perrhenate.

The title compound, [Re(2)(OH)(C(10)H(8)N(2))(2)(CO)(6)][ReO(4)], is a mixed-valence rhenium compound containing discrete anions and cations. The Re(I) atoms are in a slightly distorted octa-hedral environment, whereas the Re(VII) atoms show the typical tetra-hedral coordination mode. The dihedral angle between the two bipyridine groups is 34.3 (7)°.

Setting ambiguity in C2/c with dibromidotetrakis(1H-pyrazole-kappaN2)manganese(II) as an example.

trans-Dibromidotetrakis(1H-pyrazole-kappaN(3))manganese(II), [MnBr2(C3H4N2)4], crystallizes in the C2/c space group with the Mn atom located on a centre of inversion. As a result, there is just one half-molecule in the asymmetric unit. Geometric parameters are in the usual ranges. The Mn centre is octahedrally coordinated by four pyrazole residues in the equatorial plane and by two bromide ligands in the axial positions. The molecular conformation is stabilized by N-H...Br hydrogen bonds. The structure of the title compound had already been described [Lumme & Lindell (1987). J. Coord. Chem. 15, 383-392] in a different setting, with the Mn atoms located on inversion centres on Wyckoff position d (1/4, 1/4, 1/2; 3/4, 1/4, 0; 3/4, 3/4, 1/2; 1/4, 3/4, 0). In the conventional setting, however, the Mn atoms are situated on Wyckoff position a (0, 0, 0; 0, 0, 1/2; 1/2, 1/2, 0; 1/2, 1/2, 1/2). In this special case, if the c axis has the same length as the short diagonal of the ac plane, the transformation from one setting into the other yields almost indistinguishable cell parameters, and the possibility of confusion arises. This setting ambiguity could be the reason why two structures in different settings might be taken as polymorphs even though they can easily be transformed. As a result of this, care should always be taken to use the conventional setting.

Solvent-free methylthiomethyllithium [LiCH2SMe]infinity: solid state structure and thermal decomposition.

Solvent-free [LiCH2SMe]infinity forms a layer structure consisting of four- (Li2C2), five- (Li2CS2), and six-membered (Li2C2S2) rings in the solid state; the compound violently explodes upon heating to T=160+/-5 degrees C under an argon atmosphere.