1, 1′-(3-Oxapentamethylene)dicyclopentadiene [O(CH2CH2C5H5)2] (1), containing a flexible chain-bridged group, was synthesized by the reaction of sodium cyclopentadienide with bis(2-chloroethyl) ether through a slightly modified literature procedure. Furthermore, the binuclear cobalt(III) complex O[CH2CH2(η5-C5H4)Co(CO)I2]2 (3) and insoluble polynuclear rhodium(III) complex {O[CH2CH2(η5-C5H4)RhI2]2}n (8) were obtained from reactions of 1 with the corresponding metal fragments and they react easily with PPh3 to give binuclear metal complexes, O[CH2CH2(η5-C5H4)Co(PPh3)I2]2 (4) and O[CH2CH2(η5-C5H4)Rh(PPh3)I2]2 (9), respectively. Complexes 3, 4 and 9 react with bidentate dilithium dichalcogenolato ortho-carborane to give eight binuclear half-sandwich ortho-carboranedichalcogenolato cobalt(III) and rhodium(III) complexes O[CH2CH2(η5-C5H4)Co(PPh3)(E2C2B10H10)]2 (E = S (5a) and Se (5b)), O[CH2CH2(η5-C5H4)]2Co2(E2C2B10H10) (E = S (6a) and Se (6b)), O[CH2CH2(η5-C5H4)Co(E2C2B10H10)]2 (E = S (7a) and Se (7b)) and O[CH2CH2(η5-C5H4)Rh(PPh3)(E2C2B10H10)]2 (E = S (10a) and Se (10b)). All complexes have been characterized by elemental analyses, NMR spectra (1H, 13C, 31P and 11B NMR) and IR spectroscopy. The molecular structures of 3, 5a, 6a, 6b, 9 and 10b were determined by X-ray diffractometry.