Phosphorus-containing podands

1.	Using a conductometric method in a mixed THF-CHCl3 solvent, the complex-forming abilities of bis(ortho-(diethoxyphosphinylmethoxy)phenyl) ethers of oligoethylene glycols towards alkali metal cations have been studied. Complex-forming ability towards Li+, Na+, K+, and Rb+ cations depends very much on the length of the polyether chain. In the case of the Cs+ cation the effectiveness increases monotonically with increase in the number of ethylene glycol units.
2.	The complex-forming abilities of the higher members of the series of podands studied — bis(ortho-(diethoxyphosphinylmethoxy)phenyl) ethers of tetraethylene glycol and pentaethylene glycol — towards K+, Rb+, and Cs+ cations are comparable with, and in some cases exceed, those for 18-crown-6 and dibenzo-18-crown-6.
3.	The enhanced effectiveness of the present class of podands (in comparison with podands with ortho-diethoxyphosphinylphenyl terminal groups) towards alkali metal cations of greater radius (K+, Rb+, Cs+) is explained by the participation of the O atom located at the -position to the phosphoryl group in the coordination.

For previous communications, see 1, 2].