A SYNTHETIC, STRUCTURAL AND NMR SPECTROSCOPIC STUDY ON 1,3-DISTANNA-2-CHALCOGENA-[3]FERROCENOPHANES

Three synthetic routes to the first 1,3-distanna-2-chalcogena-[3]ferro cenophanes are described and their H-1, C-13, Se-77, Sn-119 and Te-125 NMR solution spectra are reported The reaction of either 1,1'-bis(chl orodimethylstannyl)ferrocene (1) with the chalcogenide Li2E (E = O, S, Se, Te) or 1,1'-bis(dimethylstannyl)ferrocene (2) with the chalcogen E (E = O, S, Se, Te) as well as the insertion of chalcogen into the ti n-tin bond of 1,1,2,2-tetramethyl-1,2-distanna-[2]ferrocenophane (3) a ll give the corresponding 1,3-distanna-2-chalcogena-[3]ferrocenophane, Fe(C5H4SnMe2)(2)E (E = O (4), S (5), Se (6) and Te (7)), in reasonabl e yields (> 50%). The X-ray structure determinations of 6 and 7 indica te that the size of the chalcogen has a decisive influence upon the ge ometry of the sandwich moiety. Thus, the cyclopentadienyl rings are bo th bent away from the SnESn bridge in 6 (alpha = 3.4 degrees) and 7 (a lpha = 4.3 degrees). The rings adopt a nearly staggered conformation i n the selenium complex 6 (twist angle tau = 27.5 degrees) but are almo st eclipsed in the two crystallographically independent molecules of t he tellurium compound, 7A (tau = 4.8 degrees) and 7B (tau = 4.4 degree s).