D.N. Reinhoudt

Chemistry of crown ethers: Synthesis of crown ethers based on α,β-bis(halomethyl)- or α,β-bis(hydroxymethyl)-substituted aromatics

Abstract Two types of novel crown ethers in which a polyether chain is linked, via C atoms, with two adjacent C atoms of an aromatic or heteroaromatic ring have been synthesized by reaction of α,β-bis(halomethyl)-substituted aromatics with polyethylene glycolates. Both 1:1 and 2:2 cyclic reaction products were formed, in yields varying from 1 to 53% and from 0 to 24%, respectively. The relatively high yields of these macrocyclic polyethers (rings containing from 11 to 34 atoms), obtained without operating at high dilution, depend both on the chain length of the glycol and on the nature of the cation. This can be explained in terms of a “template” effect of the cation in the cyclization step. Experimental evidence supporting such an effect was obtained from the relationship between the 1:1 product selectivity and the glycol chain length for cations with different ionic radii (L + , Na + and K + ). Furthermore, a correlation has been established between the ratio of the yields of 1:1 and 2:2 cyclic products from the reaction of 1,2-bis(bromomethyl)benzene and dipotassium triethylene glycolate and the ratio of the relative complexation constants of these compounds with potassium salts.

Chemistry of crown ethers: Complexation with alkali metal trichloro(ethylene)platinum(II) salts

Abstract A novel method has been developed for the determination of the complexation constants of crown ethers with alkali salts. It comprises the equilibration of crown ether ( 1–7 ) solutions in deuterochloroform with solid trichloro(ethylene)platinum(II) salts (Na + , K + , Rb + , Cs + ) and the PMR spectroscopic determination of the equilibrium ratio of complex to free crown ether from the relative intensities of the ethylene and crown ether protons. The solubility of uncomplexes salt was determined independently by atomic absorption spectrometry. The major advantages of this method over others are: (i) complexation constants in apolar solvents are obtained from a direct solid-liquid transition, (ii) the cation in the salt can be varied, and (iii) a simple detection technique can be used for monitoring the complexation. The PMR spectra indicate that there are three types of complex, depending on the ratio of the diameter of the crown ether cavity to that of the cation. If this ratio is small ( 1.0) the polyether ring is twisted around the cation.

Interaction of thiirene 1,1-dioxides with transition metal complexes

Abstract The decomposition of thiirene 1,1-dioxides into sulphur dioxide and the corresponding acetylenes is catalysed by certain transition metal complexes [Pd 0 Pt 0 and Ir 1 ]. The metal complexes of the substrate are key intermediates in the decomposition. A possible pathway is suggested.