James F. Britten

Supramolecular macrocycles reversibly assembled by Te … O chalcogen bonding

Organic molecules with heavy main-group elements frequently form supramolecular links to electron-rich centres. One particular case of such interactions is halogen bonding. Most studies of this phenomenon have been concerned with either dimers or infinitely extended structures (polymers and lattices) but well-defined cyclic structures remain elusive. Here we present oligomeric aggregates of heterocycles that are linked by chalcogen-centered interactions and behave as genuine macrocyclic species. The molecules of 3-methyl-5-phenyl-1,2-tellurazole 2-oxide assemble a variety of supramolecular aggregates that includes cyclic tetramers and hexamers, as well as a helical polymer. In all these aggregates, the building blocks are connected by Te…O–N bridges. Nuclear magnetic resonance spectroscopic experiments demonstrate that the two types of annular aggregates are persistent in solution. These self-assembled structures form coordination complexes with transition-metal ions, act as fullerene receptors and host small molecules in a crystal.

Structure of an unusual 5:2 methylmercury: adenine complex

The [(CH 3 Hg) 5 Ad 2 ](NO 3 )3·3H 2 O compound is monoclinic, P 2 1 / c , a = 10.717(7), b = 26.680(8), c = 11.778(2) A, β= 102.59(4)°, Z =4. The structure was solved on 2841 observed reflections to R = 0.045. The crystal contains an equal number of N7, N9-bonded [(CH 3 Hg) 2 Ad] + ions and N3,N7,N9- bonded [(CH 3 Hg) 3 Ad] 2+ ions joined into dimers via pairs of complementary N6ue5f8H⋯1 hydrogen bonds. The [(CH 3 Hg) 3 Ad] 2+ ion is also found in crystals of [(CH 3 Hg) 3 Ad] (NO 3 ) 2 ·H 2 0: triclinic, P , a = 7.017(3), b = 11.345(6), c = 12.722(3) A, α= 64.91(3), β = 87.50(3), γ= 89.59(4)°, Z = 2, R = 0.057, 1960 observed reflections. The 1 H and 13 C NMR spectra of the 5:2 complex in DMSO-d 6 contain only one set of proton signals for the adenine ring and the CH 3 Hg + ions. This indicates that the complexes exchange their stoichiometries rapidly on the NMR time scale. In addition, the CH 3 Hg + cations are shuffled among the five unequivalent coordination sites.

N,N-dimethylacetamide adducts of mixed iodo-ammine complexes of platinum(II) and platinum(IV)

Abstract As a route to purify mixed iodo-ammine complexes of Pt, the N,N -dimethylacetamide (DMA) solvates cis -(NH 3 ) 2 PtI 2 ·DMA, trans -(NH 3 ) 2 PtI 2 ·3DMA, cis - and trans -(NH 3 ) 2 PtI 4 ·3DMA, and the mixed-valence compound cis -(NH 3 ) 2 PtI 2 · cis -(NH 3 ) 2 PtI 4 ·2DMA were prepared. Crystals of cis -(NH 3 ) 2 PtI 2 ·DMA are monoclinic, P 2 1 / c , a = 8.443(4), b = 12.691(6), c = 12.150(9) A, β = 105.12(7) A, Z = 4. The structure was solved on 2035 unique Mo K α reflections to R = 0.044. The compound reveals well separated square planar cis -(NH 3 ) 2 PtI 2 and DMA units. The crystals are unstable to loss of DMA. A three-dimensional hydrogen-bonding network involving the ammines, the iodine atoms, and the carbonyl groups of DMA determines the crystal structure. The infrared spectra indicate that the DMA molecule is not coordinated to platinum in these compounds.

An investigation of (C5H5)Fe(C5H4–C(OBF3)–CH3)1,2

Acetylferrocene readily forms an adduct with BF3. The product is a neutral model for protonated acetylferrocene, a species that is a crucial intermediate in the formation of 1,3,5-trisferrocenyl-benzene and other conjugated heterometallic derivatives by cyclocondensation. The title compound’s structure was determined in the solid state by X-ray diffraction and its spectroscopic properties were examined in detail, particularly the electronic excitation spectrum, which confirms the previous identification of the in situ generated protonated ketone.

3,4-Dimethyl-1,1-bis[4-(trifluoromethyl)phenyl]-2,5-dihydro-1H-germole

The interxadnal C—Ge—C bond angle in the germacycloxadpentene ring of the title compound, C20H18F6Ge or [Ge(C6H10)(C7H4F3)2], is 93.17u2005(9)°.

Tetrakis(cyclopentamethylenedithiocarbamate-S,S ′)technetium(v) bromide, an unusual eight-coordinate complex of technetium(v)

Reaction of the ligand dicyclopentamethylenethiuram disulfide with n[NBu n 4 n][TcOCl n 4 n] results in the formation of a unique neight-coordinate technetium(V) species.