ORGANOMETALLIC COMPOUNDS AS COMPLEXING AGENTS - A RARE EXAMPLE OF A CRYSTALLINE ALKALI-METAL PODATE

The tentacle-bearing ferrocenes [Fe{R(4)C(5)SiMe(2)(OCH2CH2)(n)OMe}(2) ] (4a: R = H, n = 2; 4b: R = Me, n = 2, 4c: R = H, n = 3, 4d:R = Me, n = 3) and [Fe{Me(4)C(5)(CH2)(3)(OCH2CH2)(3)OMe}(2)] (5) act as podands for alkali metal cations; 4b, 4d, and 5 are much better podands than 4a and 4c. Compound 5 and [(C5K5)Fe{Me(4)C(5)(CH2)(3)(OCH2CH2)(3)OMe}] (8) are oxidized to 5(+) [PF6](-) and 8(+) [PF6](-), respectively, wh ich both show no tendency to crystallize. The cobaltocenium species o{ Me(4)C(5)(CH2)(3)(OCH2CH2)(3)OMe}(2)](+)[PF6](-) (11(+) [PF6](-)) is a selective podand, which prefers potassium over lithium cations; its p otassium pedate 11(+) [PF6](-) K+[PF6](-) is the first example of a crystalline oligoethylene glycol ether podate, whose crystallinity doe s not rely on the rigid end-group principle. (C) 1997 Elsevier Science Ltd.