Paul A. Cooke

Copper(I) iodide coordination networks–controlling the placement of (CuI)∞ ladders and chains within two-dimensional sheets

Abstract Reaction of copper(I) iodide with a range of bridging bidentate N-donor ligands is reported. CuI reacts with L [L = pyrazine (pyz) 1, 1,2-trans-(4-pyridyl)ethene (bpe) 2, quinoxaline (quin) 3, 4,4′-bipyridyl (4,4′-bipy) 4, pyrimidine (pym) 5, 4,7-phenanthroline (4,7-phen) 6] in MeCN to afford insoluble yellow powders of stoichiometry [(CuI)2(L)]∞ 1–6, respectively. Single crystal structure determinations on compounds 1–3, 5, and 6 confirm constructions based on (CuI)∞ staircase ladders linked by bridging ligands to afford two-dimensional sheets. The separation of the (CuI)∞ ladders can be controlled by simple variation of the length of the ligands. In 5 and 6 the two-dimensional sheets undulate due to the angle between the N-donors of the ligand. [(CuI)(diaz)]∞ 7 (diaz = 2,7-diazapyrene), formed by reaction of CuI with diaz in PhCN and CH2Cl2, has a split-staircase motif for the (CuI)∞ moiety, while [(CuI)(4,4′-bipy)]∞ 8, formed by the reaction of CuI with the ligand in DMSO and CH2Cl2, shows rhomboid dimers of (CuI)2 linked by bridging ligands to give honeycomb sheets that are perpendicularly interpenetrated.

Poly-orthophenylenes: Synthesis by suzuki coupling and solid state helical structures

Abstract The preparation of ortho-polyphenylene oligomers, having 3–9 rings, using a rational Suzuki coupling strategy, has been achieved, and a helical structure determined for a number of these products by X-ray crystallography.

Highly enantioselective synthesis of chiral imides and derived products via chiral base desymmetrisation

The enantioselective deprotonation of several ring-fused imides with a chiral base, followed by electrophilic quenching, gives a range of chiral products in good yield and in ≥91% ee. The absolute stereochemistry of two of the products was determined by X-ray crystallography. A number of the imide products were subjected to further, highly regioselective, transformations, including enolate substitution, reduction and thionation.

S-CYLINDROPHANES : FROM METAL TWEEZERS TO METAL SANDWICHES

Inclusion of AgIand CuIions by the preorganized cylindrophane cage compound 1 provides the first examples of bis(η6) sandwich complexes of these metals. Locked in a trigonal-planar heteroatom ligand field, the guest ions are shown by NMR spectroscopy to withdraw electron density from the aromatic rings. A statistical study of η6 coordination in the solid state supports the description of arene–metal contacts between 2.5 and 3.5 A as bonds.

Synthesis of a chiral adamantoid network— the role of solvent in the construction of new coordination networks with silver(I)

Depending on the crystallisation solvent used, reaction of 2,2′-bipyrazine with AgBF4 results in the formation of either a chiral three-dimensional adamantoid coordination network or a two-dimensional sheet incorporating five coordinate Ag(I) ions.

Silver(I)–3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine coordination polymers: a diversity of chain motifs

Abstract The influence of solvent and anion on the formation of coordination polymers between silver(I) and 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3′-pytz), a bridging ligand that can adopt both cisoid and transoidconformations, is reported. Reaction of AgPF6 in MeCN with 3,3′-pytz in CH2Cl2 gives ([{Ag(NCMe)2}(μ-3,3′-pytz)][PF6]·MeCN)∞, 1, of AgPF6 in MeNO2 and 3,3′-pytz in CH2Cl2 gives ([{Ag2(μ-3,3′-pytz)2}(μ-3,3′-pytz)][PF6]2·4MeNO2)∞, 2, and of AgCF3SO3 in MeCN and 3,3′-pytz in CH2Cl2 gives {[Ag(μ-3,3′-pytz)]CF3SO3}∞, 3. These cationic coordination polymers exclusively form chain structural motifs. That in 1, ([{Ag(NCMe)2}(μ-3,3′-pytz)]+)∞, has a castellated construction with each tetrahedral silver(I) center coordinated by two solvent molecules as well as two linking transoid-oriented 3,3′-pytz bridges (Ag⋯Ag 13.210 A) in a 1:1 polymeric chain. That in 2, ([{Ag2(μ-3,3′-pytz)2}(μ-3,3′-pytz)]2+)∞, is novel. It is the first coordination polymer to exhibit both cisoid and transoid conformations of a bridging ligand coordinated to the same metal center. Pairs of silver(I) centers are linked by pairs of cisoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 11.695 A) to form [Ag2(μ-3,3′-pytz)2] motifs, which are bridged, in turn, by transoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 13.318 A) to form a 3:2 ligand:metal infinite polymeric zigzag chain. That in 3, {[Ag(μ-3,3′-pytz)]+}∞, has a zigzag architecture despite being based on linear silver(I) centers. Transoid-oriented 3,3′-pytz molecules link silver(I) centers (Ag⋯Ag 13.225 A) to give a 1:1 ligand:metal infinite polymeric zigzag chain. The chains aggregate in parallel pairs linked by weak Ag⋯Ag contacts (Ag⋯Ag = 3.220 A), which are supported by (μ2-κO,κO′) bridging CF3SO3− anions.

Contrasting Nonclassical Silicon−Hydrogen Interactions in Niobium and Tantalum Half-Sandwich Complexes: Si−H···M Agostic versus M−H···Si−Cl Interligand Hypervalent Interactions

Reaction of [CpM(NAr)(PMe3)2] (M = Nb, Ta; Ar = 2,6-C6H3iPr2) with HSiClMe2 gives two remarkably different nonclassical Si···H···M products depending only on the identity of M; [CpTa(NAr)(H)(SiMe2Cl)(PMe3)] possesses an unusual electron-rich M−H···Si interligand hypervalent interaction while [CpNb{η3-N(Ar)SiMe2−H}Cl(PMe3)] is the first example of a β-agostic silylamine Si−H···M interaction showing a “stretched” Si−H bond.

S-Cylindrophane: von pinzettenähnlich strukturierten Metallkomplexen zu Sandwichkomplexen

Der Einschlus von AgI- und CuI-Ionen durch das praorganisierte Cylindrophan 1 fuhrte zu den ersten Bis(η6)-Sandwichkomplexen dieser Metalle. NMR-spektroskopisch wurde nachgewiesen, das die durch die Heteroatome trigonal-planar koordinierten Gast-Ionen die Elektronendichte an den aromatischen Ringen verringern. Nach den Ergebnissen einer statistischen Studie der η6-Koordination in Festkorpern konnen Aren-Metall-Wechselwirkungen mit Abstanden von 2.5 bis 3.5 A tatsachlich als Bindungen angesehen werden.

Structure and total synthesis of benzylthiocrellidone, a novel dimedone-based vinyl sulfide from the sponge Crella spinulata

A concise synthesis of the yellow pigment benzylthiocrellidone 1, based on a Michael addition–elimination of dimedone 2 to the ketene thioacetal 7 derived from dimedone, benzyl bromide and carbon disulfide, is described. The synthetic pigment had an X-ray crystal structure identical to that measured for the natural product.

Rearrangement of ammonium ylides produced by intramolecular reaction of catalytically generated metal carbenoids. Part 2. Stereoselective synthesis of bicyclic amines

Ammonium ylides produced by intramolecular reaction of copper carbenoids tethered to cyclic allylic amines undergo [2,3]-rearrangement to deliver bicyclic amines. The reaction can be performed using a cyclic N-allylamine in which the diazo group is tethered adjacent to nitrogen, or a vinyl-substituted cyclic amine in which the diazo group is N-tethered to the ring. In the former type of reaction, stereoselective ylide formation and rearrangement usually delivers high levels of diastereocontrol. In the latter case, efficient ‘chirality transfer’ can be accomplished when the reaction is performed using an enantiomerically pure substrate. The reactions have been used to construct pyrrolizidine, indolizidine and quinolizidine systems, and the CE sub-unit found in the manzamine and ircinal alkaloids.