Coupling reactions of ferrocenylacetylene with mononuclear metal carbonyls Fe(CO)(5) and M(CO)(6) (M = Mo, W): Synthesis and characterization of [Fe(CO)(2){eta(5)-2,5-Fc(2)C(5)H(2)CO}C(Fc)=CH], [Fe(CO)(2){eta(2):eta(2)-2,5-Fc(2)C(4)H(2)Fe(CO)(3)}-mu-CO], [Fe(CO)(3){eta(2):eta(2)-2,5-Fc(2)C(4)H(2)CO}], 1,2,4-triferrocenylbenzene, 2,5-diferrocenylthiophene, and 2,5-diferrocenylselenophene

Thermolysis of a benzene solution containing Fe(CO)5 and ferrocenylacetylene yielded three new compounds: [Fe(CO)(2){eta(2):eta(5)-2,5-Fc(2)C(4)H(2)CO}C(Fc)=CH] (1), [Fe(CO)(2){eta(2):eta(2)-2,5-Fc(2)C(4)H(2)Fe(CO)(3)}-mu-CO] (2), and [Fe(CO)(3){eta(2):eta(2)-2,5-FC2C4H2CO}] (3). When a benzene solution containing ferrocenylacetylene and M(CO)(6) (M = Mo, W) was refluxed, 1,2,4-triferrocenylbenzene (4) was formed. In contrast to the reaction of ferrocenylacetylene with Fe(CO)(5), which leads to cyclization with insertion of a CO molecule, in the reaction with M(CO)(6) no insertion of CO takes place during cyclization. However, if the reactions with M(CO)(6) are carried out in the presence of S-8-powder or Se-powder, insertion of these chalcogen atoms during cyclization does take place and 2,5-diferrocenylthiophene (5) and 2,5-diferrocenylselenophene (6) are formed respectively, along with 4. All new compounds were characterized by IR and H-1 and C-13 NMR spectroscopy. Structures of 1-5 were established by single-crystal X-ray crystallography