Medium size macrocycles incorporating combinations of coordinated-1,3-diyne units, oxygen donors and group 14 elements

Two approaches have been employed to prepare medium size macrocycles incorporating combinations of coordinated-1,3-diyne units, oxygen donors and group 14 elements. In the first approach, the acid-catalysed reaction of [{Co2(CO)6(μ-η2-HOCH2Ctriple bond; length of mdashCsingle bond)}2] (1a) with either C6H5OH, C6H4-1,4-(OH)2 or C6H4-1,2-(OH)2 was found to form in good to moderate yield the nine-membered [{Co2(CO)6}2{cyclo-μ-η2:μ-η2-CH2C2C2CH2OC6H4}2] (2) and the eight-membered macrocycles, [{Co2(CO)6}2{cyclo-μ-η2:μ-η2-CH2C2C2CH2-2,3-C6H2-1,4-(OH)2}] (3) and [{Co2(CO)6}2{cyclo-μ-η2:μ-η2-CH2C2C2CH2-3,4-C6H2-1,2-(OH)2}] (4), respectively. In contrast, treatment of the bis-lithiated derivative of 1a with Cl2SiR1R2 affords the silicon-containing nine-membered macrocycles [{Co2(CO)6}2{cyclo-μ-η2:μ-η2-OCH2C2C2CH2OSiR1R2}] (5a R1 = R2 = Me; 5b R1 = R2 = Ph; 5c R1 = Me, R2 = Ph). Similarly, the germanium analogue of 5b, [{Co2(CO)6}2{cyclo-μ-η2:μ-η2-OCH2C2C2CH2OGePh2}] (6) can be prepared from Cl2GePh2. Single crystal X-ray diffraction studies have been reported on 2, 3, 5a, 5b and 6.