Aliphatic polyketones as classic yet new molecular ropes for structural diversity in organic synthesis

Polyketone compounds play an important role in organic chemistry as a prominent source of reactivity and functionality. Their chemical properties vary widely depending on the ketone sequence in carbon chains. Although vicinal and β-polyketones have been used for more than 150 years, the recent development of new ketone sequences composed of alternating 1,3- and 1,4-diketones has demonstrated the further potential of polyketones as structurally flexible molecular ropes capable of derivatization to π-conjugated chromophores and molecular assemblies. In this Feature Article, we review the synthetic strategies and reactivities of polyketones with respect to their ketone sequence. Furthermore, recent research on polyketones with hybrid ketone sequences is also discussed, focussing on their structural diversity in chemical transformations including intramolecular cyclization and stereoselective oxidation.

Coordination polymers of CdII and PbII with croconate show remarkable differences in coordination patterns: a structural and spectroscopic study

The croconate dianion is a highly versatile ligand with two tautomeric forms making it useful for building large superstructures in the solid state. The single-crystal X-ray structures of Pb^II- and Cd^II-croconate coordination polymers, namely catena-poly[[[diaqualead(II)]-μ-croconato-κ⁴O¹,O²:O³,O⁴] monohydrate], {[Pb(C₅O₅)(H₂O)₂]·H₂O}_n, 1, and catena-poly[[triaquacadmium(II)]-μ-croconato-κ⁴O¹,O²:O³,O⁴], [Cd(C₅O₅)(H₂O)₃]_n, 2, have been determined. Both polymers form one-dimensional (1D) structures; 1 is a nonplanar 1D zigzag coordination polymer extended along the crystallographic b axis, whereas 2 is a planar 1D ribbon parallel to the [101] direction. In 2, three H₂O molecules are coordinated directly to the metal atom, while in 1, only two H₂O molecules are directly coordinated to the metal atom. A third interstitial H₂O molecule is involved in hydrogen bonding with O atoms of the croconate ligands of an adjacent layer and other H₂O molecules, resulting in stacked double layers parallel to the [105] plane. Solid-state FT-IR and solution UV-Vis spectra also substantiate the croconate coordination.

Crystal structure of dimethanol-(μ2-squarato-κ2 O:O′)-tetrakis(tri-p-tolylphosphane-κP)disilver(I) – methanol (1/2), C92H98Ag2O8P4

C92H98Ag2O8P4, triclinic, P1̄ (no. 2), a = 11.179(3) Å, b = 12.623(3) Å, c = 15.656(4) Å, α = 83.607(8)°, β = 78.636(9)°, γ = 83.128(9)°, V = 2141.6(10) Å3, Z = 2, R gt(F) = 0.0398, wR ref(F 2) = 0.1034, T = 294(2) K.

Crystal structure of poly[μ2-aqua-aqua-(μ2-4-nitro-2,5,6-trioxo-1,2,5,6-tetra-hydro-pyridin-3-olato)hemi-μ4-oxalato-barium(II)]

In the title coordination polymer, [Ba(C5HN2O6)(C2O4)0.5(H2O)2] n , the tenfold coordination of the Ba centre consists of four O atoms from the two 4-nitro-2,5,6-trioxo-1,2,5,6-tetra-hydro-pyridin-3-olate (L) anions, three O atoms of two oxalate anions and three water mol-ecules. The Ba-O bond lengths fall in the range 2.698 (3)-2.978 (3) Å. The L ligand chelates two Ba atoms related by a screw axis, leading to formation of fused five- and six-membered chelate rings. Due to the bridging function of the ligands and water mol-ecules, the complex monomers are connected into polymeric two-dimensional layers parallel to the bc plane. Inter-molecular O-H⋯O hydrogen bonds link these layers into a three-dimensional supra-molecular framework.

An organic anion template: a 24-nucleus silver cluster encapsulating a squarate dimer

An unprecedented organic anion templated silver cluster has been isolated, leading to unusual π–π interaction within the encapsulated squarate dimer.