A new type of chiral pentacoordinated silicon compounds with azomethine ligands made from acetylacetone and amino acids

The crystal structure of trichlorido[N-[(2-oxyphenyl)methylidene]phenylglycinemethylester-κ3 O,N,O′]-tin(IV) – methylene chloride (1/1), C16H14Cl3NO3Sn·CH2Cl2

C16H14Cl3NO3Sn·CH2Cl2, monoclinic, P21/n (no. 14), a = 11.1341(4) Å, b = 10.5867(2) Å, c = 18.6979(6) Å, β = 93.126(3)°, V = 2200.7(1) Å3, Z = 4, R gt(F) = 0.0405, wR ref (F 2) = 0.0847, T = 213 K.

A stable zinc–organic framework with luminescence detection of acetylacetone in aqueous solution

A stable Zn-based MOF has been prepared, presenting the first example of a recyclable luminescent sensor for recognizing acetylacetone in aqueous solution.

Chiral Control in Pentacoordinate Systems: The Case of Organosilicates

Chirality at the central element of pentacoordinate systems can be controlled with two identical bidentate ligands. In such cases the topological Levi-Desargues graph for all the Berry pseudorotations (BPR, max. 20) reduces to interconnected inner and outer "circles" that represent the dynamic enantiomer pair. High enough barriers of the BPR crossovers between the two circles is all what is needed to ascertain chiral integrity. This is illustrated computationally and experimentally for the organosilicates 7 and 10 that carry besides a Me (a), Et (b), Ph (c), or F (d) group two bidentate 2-(phenyl)benzo[ b]-thiophene or 2-(phenyl)naphthyl ligands, respectively. The enantiomers of tetraorganosilane precursor 9 could be separated by column chromatography. Their chiral integrity persisted on forming the silicates. CD spectra are reported for 10c. Fluoro derivative 10d is shown to have its electronegative F substituent in an equatorial position, is stable toward hydrolysis, and its enantiomers do not racemize at ambient temperatures, while those of 10c racemize slowly.

2-Acylpyrroles as mono-anionic O,N-chelating ligands in silicon coordination chemistry

Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole (L(1)H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L(1)2SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L(1)2SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L(1)2SiCl2, L(1)2SiF2, L(1)2Si(OTf)2, L(1)2SiPhCl, and L(1)2SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L(1)3Si(+) and L(1) SiPh(+) were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L(1)2SiCl2 with a third equivalent of L(1)H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated C-C coupling of two ligands L(1).