<Emphasis Type="Italic">Trans</Emphasis>-dibromodioxodimethylformamide molybdenum(VI) MoO<Subscript>2</Subscript>Br<Subscript>2</Subscript>(OCHNMe<Subscript>2</Subscript>)<Subscript>2</Subscript>

The molecular structure of trans-dibromodioxodimethylformamide molybdenum(VI), MoO₂Br₂(OCHNMe₂)₂ has been determined. Crystal data: Triclinic, P-1, a = 12.3005(2), b = 15.8763(4), c = 21.1653(6) ?, α = 71.992(1)°, β = 88.966(2)°, γ = 89.999(1)°, V = 3930.1(2) ?, Z = 12. Trans-dibromodioxodimethylformamide molybdenum(VI) was obtained by the reaction of sodium molybdate, HBr and dimethylformamide and was characterized by IR, and ¹H NMR spectroscopy and elemental analysis.     

Synthesis and crystal structure of bis(2,2′-bipyridyl)mononitritozinc(II) perchlorate. An example of a six-coordinate cis-octahedral ZnN4O2 chromophore

The crystal structure of bis(2,2-bipyridyl)mononitritozinc(II) perchlorate, [Zn(bipy)₂ (ONO)][ClO₄] (1) has been determined. The complex is monoclinic, with a = 10.9195(4) Å, b = 12.2320(5) Å, c = 16.5477(8) Å, = 105.6150(10), P2₁/n space group, with final R1 = 0.0657 and wR2 = 0.1630. The complex involves a [Zn(bipy)₂ (ONO)]⁺ cation and a [ClO₄]^– anion. The ZnN₄O₂ chromophore is six-coordinate, with a cis-distortion of the two oxygens of the nitrite, O(1) and O(2), at distances 2.216(5) and 2.197(5) Å from the zinc (Zn– O _mean = 2.206(5) Å, O = 0.019(5) Å) and two out of plane Zn–N bonds, Zn–N(2) and Zn–N(3), at 2.129(4) and 2.135(4) Å (Zn–n _mean/out = 2.132(4) Å, n _2,3 = 0.006(4) Å). The two inplane nitrogens, N(1) and N(4), at distances Zn–N(1) = 2.090(4) and Zn–N(4) = 2.085(4) Å (Zn–n _mean/in = 2.087(4) Å, n _1,4 = 0.005(4) Å) are greater than 2.0 Å, but slightly shorter than the axial bonds. The inplane angles ₁, ₂, and ₃ in 1 have values 150.33(18), 108.98(17), and 99.73(18) respectively. The stereochemistry is cis-distorted octahedral, with an ₃ = 99.37(18), which is lower than ₃ = 103.4(1) observed in [Zn(bipy)₂(ONO)][NO₃] (5). Comparison with the corresponding [Cu(bipy)₂(ONO)][Y] complexes suggested that the cis-distortion of the CuN₄O₂ chromophore in the copper(II) series does not originate in the Jahn–Teller or pseudo-Jahn–Teller effect.     

Crystal structure of [WI2(CO)3{P(OMe)3}2]

[WI₂(CO)₃{P(OMe)₃}₂]crystallizes in the orthorhombic space group Pca2₁, with a = 26.924(5), b = 10.726(2), c = 14.136(3) Å, and Z = 8. There are two molecules in the asymmetric unit, the metal atoms in each case being seven-coordinate with a capped fac-(CO)₃ octahedral geometry. The molecular dimensions in the two molecules are nearly identical. The W–P distance to the capping atom 2.397 Å (average) is significantly shorter than the other W–P distance, 2.525 Å (average).     

On the highly stereoselective addition of lithio-acetylides to α-hydroxy-ketones

Addition of 2 equiv of a lithio-acetylide to an unprotected α-hydroxy ketone is extremely stereoselective in examples where the two ketone substituents are relatively large.     

Fluorinated tertiary alkoxides of some lanthanides: tris-trifluorotertiarybutoxides of lanthanum, praseodymium and europium

From reactions involving M{N(SiMe₃)₂}₃ (M = La, Pr and Eu) and triflurotertiary butano[(CF₃)Me₂COH; tftb.H], the compounds [La(tftb)₃(thf)_1.5] (1), [Pr(tftb)₃ (2) and [Eu(tftb)₃] (3) have been isolated. From variable temperature ¹H and ¹⁹F NMR studies it is suggested that 1 is a mixture of [La₃(tftb)₉(thf)₂] (1a) and [La₂(tftb)₆(thf)₄] (1b). X-ray crystallography has shown that 2 is the trimer [Pr₃(tftb)₉] and variable temperature ¹H and ¹⁹F NMR suggests that 3 is also a trimer, [Eu₃(tftb)₉].     

The crystal and molecular structure of hexadecaphenyloctasiloxyspiro(9,9)titanate(IV)

The crystal and molecular structures of the title compound have been determined by single crystal X-ray diffraction methods. In the spiro molecule, the metal atom has a geometry very close to tetrahedral, with OTiO angles of 107.9–111.0(2)° and very short TiO bonds of length 1.777–1.791(5)Å. The two TiO₅Si₄ rings have different, ill-defined conformations; the SiO bond lengths and SiOSi angles are similar to those in (SiO)_n rings.     

The X-ray crystal structure of the organoplatinum bridging diselenide complex [(PtMe3I)2MeSeSeMe]

An X-ray crystal structure determination of the dinuclear complex [(PtMe₃I)₂MeSeSeMe] confirms the retention of the Se—Se bond and the presence of a bridging diselenide ligand.