Synthesis, Characterization, and Theoretical Studies of New Alkynylferrocene and -biferrocene Ligands and Their Platinum-Containing Dimers and Oligomers

A series of disubstituted alkynylferrocenyl and -biferrocenyl ligands (1−4) have been synthesized and these then utilized to form a number of di-, tri-, and oligomeric platinum-containing alkynyl species (5−10). Characterization by spectroscopy and X-ray crystal structure determinations of [{C₅H₄FeC₅H₄C⋮CH}₂] (3), [C₆H₅{(C₂H₅)₃P}₂PtC⋮CC₅H₄FeC₅H₄C⋮CPt{P(C₂H₅)₃}₂C₆H₅] (5), and [(C₆H₅Pt{P(C₂H₅)₃}₂C⋮C{C₅H₄Fe(C₅H₄)₂FeC₅H₄}C⋮CPt{P(C₂H₅)₃}₂C₆H₅)] (8) illustrates their “rigid-rod” symmetrical geometries, featuring staggered cyclopentadienyl rings and almost perfect anti geometry of the ethynyl linkages in each case. Electrochemical and theoretical (extended Hückel calculations) studies on the metal complexes indicate that there is no metallocene−metallocene interaction through the alkynyl−platinum bridges.