Air-stable liquid clathrates. 1. Crystal structure of [NBu4][Br3] and reactivity of the [NBu4][Br3]·5 C6H6 liquid clathrate

[NBu₄][Br₃] interacts with C₆H₆ to form an air-stable liquid clathrate. The tribromide anion reacts with phenol to give para-bromophenol in>95% yield. The HBr which is generated in the reaction combines with the Br^– anion to form [Br-H-Br]^–. The latter forms the basis for a new liquid clathrate, [NBu₄][Br-H-Br]·n C₆H₆. The parent salt, [NBu₄][Br₃], crystallizes in the monoclinic space group C2/c witha=12.983(5),b=10.380(7),c=16.222(6) Å,=93.93(3)°, andD _c =1.47 g cm^–3 forZ=4. The final R value is 0.068 based on 787 observed reflections.     

Water-assisted self-assembly of harmonic single and triple helices in a polymeric coordination complex

A novel two-dimensional coordination polymer containing infinite, coherently pitched single and triple helical motifs is formed by the self-assembly of Cd2+, succinate, water and a bipyridyl ligand.     

The crystal structure of iododimethyl(trimethylamine)aluminum

The crystal structure of iododimethyl(trimethylamine)aluminium has been determined from single-crystal X-ray diffraction data collected by counter methods. I(CH₃)₂Al · N(CH₃)₃ crystallizes in the othorhombic space group Pnma with cell dimensions a=12.59(1), b=10.75(1), c=7.58(1)å, and p_calc=1.58 g·cm^?3 for Z=4. Least-squares refinement gave a final weighted R Value of 0.071 for 574 independet observed reflections. Each monomeric molecule lies on a crystallographic mirror plane with the trimethylamine and iododimethylaliminium groups in a staggered configuration about the aluminum  nitrogen bond.     

Crystal and molecular structure ofS-methyl(pentafluorosulfanyl)thiocarbamate

The X-ray structure of S-methyl(pentafluorosulfanyl)thiocarbamate, SF₅NHC(O)SCH₃, has been determined from three-dimensional diffractometer data and refined by full-matrix least-squares techniques. The crystals are monoclinic:P2₁/m,a=5.008 (5),b=7.811 (2),c=9.348 (4) Å, =99.08 (7)°, andZ=2; finalR=0.046 for 517 observed reflections. The structure comprises hydrogen-bonded (NHO) chains with the component monomers in thecis, cis-conformation, i.e., the arrangement of the nonhydrogen and nonfluorine atoms is nearly planar, the SF₅ group and the O are in acis position with respect to the C-NH bond, and the O and the CH₃ group are in acis position with respect to the C(O)-S bond. Theoretical methods including MNDO and molecular modeling were used to study the relative stabilities of the four possible conformations of SF₅NHC(O)SCH₃.     

Ammonium hexafluorosilicate salts

The preparation and characterization of the ammonium hexafluorosilicate salts, 2[R]⁺ [SiF₆]²⁻ (where R=piperidinium (2), methylammonium (3), quinolinium (4), acridinium (5), 2,2,6,6-tetramethylpiperidinium (6), and propylammonium (7)) is described.The salts were prepared from the reaction of the corresponding alkylammonium fluoride with silica gel. The compounds were characterized by NMR, IR, mass spectrometry and in the case of 1 (piperidinium fluoride), 2-4 by X-ray crystallography. Compounds 1-3 crystallize in the orthorhombic crystal system (space groups Iba2, Fdd2, and Pnnm, respectively), with Z=8, 14, and 4, respectively. Compound 4 crystallizes in the triclinic space group P-1, with Z=2. Compounds 1-4 exhibit hydrogen bonding.     

Reaction of early transition metal complexes with macrocycles. II. Synthesis and structure of TiCl3(H2O) · 18-crown-6, a compound with a unique bidentate bonding mode for the 18-crown-6 molecule

18-crown-6 reacts with TiCl₃ in CH₂Cl₂ to form a complex in which the crown ether functions as a tridentate ligand. Addition of moist hexane affords a molecular complex in which the crown ether functions as a bidentate ligand. A water molecule is bonded directly to the titanium atom and is further hydrogen bonded to three of the oxygen atoms of the crown. The deep blue crystals of the CH₂Cl₂ adduct belong to the monoclinic space groupP2₁/n witha=13.481(8),b=8.021(5),c=21.425(9) Å, =97.32(5)°, and _calc = 1.51 g cm^–3 forZ=4. Refinement led to a conventionalR value of 0.040 based on 873 observed reflections. The Ti–O bond distances for the crown oxygen atoms are 2.123(8) and 2.154(9) Å, while the oxygen atom of the water molecule is bonded at 2.072(8) Å. The octahedral coordination sphere of the titanium atom is completed by the three chlorine atoms at distances of 2.340(5), 2.352(4), and 2.373(4) Å. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82034 (10 pages).     

From crown ethers to zeolites: Reaction of EtAlCl2 with crown ethers

In contrast to aluminum alkyls, alkyl aluminum halides such as EtAlCl₂ react with crown ethers to form cation-anion pairs which exhibit the liquid clathrate effect. Specifically, [12-C-4·AlCl₂][AlCl₃Et] and [18-C-6·AlCl₂][AlCl₃Et] have been isolated and characterized by X-ray diffraction techniques. The cations show aluminum in an octahedral environment made up of four of the oxygen atoms from the crown and two chlorine atoms. The 12-C-4 derivative crystallizes in the monoclinic space group P2₁/c with cell constants of a=7.497(4), b=22.121(8), c=12.339(5) Å, =94.99(3)^o, and Z=4 for =1.43 g cm^–3. Least-squares refinement based on 1413 observed reflections led to a final conventional R value of 0.093. The 18-C-6 complex belongs to the triclinic space group P1 with a=8.414(4), b=12.193(6), c=12.394(6) Å, =73.14(4), =86.07(4), =81.52(4)^o, and Z=2 for =1.45 g cm^–3. Refinement based on 2605 observed reflections led to R=0.063. The complex aluminum-containing species are related to a class of compounds called aluminoxanes.     

Additions of enantiopure alpha-sulfinyl carbanions to (S)-N-sulfinimines: asymmetric synthesis of beta-amino sulfoxides and beta-alphamino alcohols

The addition of the lithium anions derived from (R)- and (S)-methyl and -ethyl p-tolyl sulfoxides to (S)-N-benzylidene-p-toluenesulfinamide provides an easy access route to enantiomerically pure beta-(N-sulfinyl)amino sulfoxides. Stereoselectivity can be achieved when the configurations at the sulfur atoms of the two reagents are opposite (matched pair), thus resulting in only one diastereoisomer, even for the case in which two new chiral centers are created. The N-sulfinyl group primarily controls the configuration of the carbon bonded to the nitrogen, whereas the configuration of the alpha-sulfinyl carbanion seems to be responsible for the level of asymmetric induction, as well as for the configuration of the new stereogenic C-SO carbon in the reactions with ethyl p-tolyl sulfoxides. An efficient method for transforming the obtained beta-(N-sulfinyl)amino sulfoxides into optically pure beta-amino alcohols, based on the stereoselective non-oxidative Pummerer reaction, is also reported.