Crown thioether chemistry: structural and conformational studies of tetrathia-12-crown-4, pentathia-15-crown-5, and hexathia-18-crown-6. Implications for ligand design

Abstract

Both compounds had NMR spectra in CDC13 identical with those of the corresponding pure enantiomers.Mineral Acid Catalyzed Asymmetric Transformations: Synthesis of (R*,S*)-1. A solution of (R*,R*)-1 (2.5 g) in chloroform (100 mL) was treated with a mixture of methanol (5 mL) and hydrochloric acid (5 mL, 10 M). After two weeks, 2.2 g (88% yield) of pure (R*,S*)-1 had separated from the mixture as long colorless needles:

Preparations for 1,4,7,11,14,17-hexa-thiacycloeicosane, 1,4,7-trithiecan-9-ol, 1,11 -dioxa-4,8,14,18-tetrathia-cycloeicosane, 1 -oxa-4,8-dithiacyclo-decane, and some complexes of iron, cobalt, nickel, and palladium

“…In [Ni(24s6)l2+, which has all six-membered chelate rings, there are two meridional loops and all others are facial as in our cation. These preferences can be related to ligand dihedral angles that are in turn influenced by intramolecular nonbonding interactions (6 (Fig. 3), the Ni-S lengths and coordination s here bond angles (Table 4) (38).…”

“…Co-S 2.444(2) C o a 2.098 (6) in [ c o (~o s~) , ]~+ , the "small ring" analogue of L3 (45) (2.320(3), 2.257(3), and 2.395(3) A), which display the expected Jahn-Teller distortion of a low-spin Co(I1) species. In the case of [co(L3)12+, which is high spin (vide infra), such distortion is not apparent.…”

“…In L1, they occur about the sulfur that separates the six-membered and the five-membered chelate rings whereas in L3 they occur about the oxygen atoms, which correspond to separators between adjacent five-membered rings. The changed arrangement of the six-membered rings undoubtedly reflects the different intramolecular nonbonded interactions in the S402 ligand (L3) compared to those in the S6 ligand (L1) (6).…”

Crystal structure of 1,2,6,7,11,12-hexathia-cyclopentadecane, C9H18S6

“…Previous studies revealed that crown thioethers possess unusual conformation behavior differing from that of oxa-crown ethers, what has important ramifications for coordination chemistry [1]. The title molecule is a new fifteen-membered macrocyclic polydisulfide composed of three repeated 1,3-propanedithiol units connected via three sulfur-sulfur bonds.…”

Metal binding studies with macrocyclic hexathioethers: Transition metal complexes of 22S6 and 20S6

“…The unusual complexation behavior of the tridentate macrocycle 1,4,7-trithiacyclononane (9S3) and related crown thioethers has also been an impetus for this development, and some specific examples of these unexpected properties include their large ligand field strengths [10,11], their ability to reduce electron-electron repulsions and thereby form low spin complexes [12][13][14][15][16][17][18][19], their ability to stabilize unusual oxidation states and coordination geometries [20][21][22][23][24][25][26][27][28] and a rapidly emerging organometallic chemistry [29][30][31][32][33][34]. Several of these thioether macrocycles including 20S6 (1,4,7,11,14,17-Nov-Dec 2001 1281 macrocycles where the exodentate conformation predominates [36][37][38]. The effect highlights the importance of pre-organization in determining the complexation mode of 9S3 and other macrocyclic thioether ligands.…”