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 drop CH}(2)] (3), [C6H5{(C2H5)(3)P}(2)PtC drop CC5H4-FeC5H4C drop CPt{P(C2H5)(3)}(2)C6H5] (5), and [(C6H5Pt{P(C2H5)(3)}(2)C drop C{C5H4Fe(C5H4)(2)FeC5H4}C drop CPt{P(C2H5)(3)}(2)C6H5)] (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 Huckel calculations) studies on the metal complexes indicate that there is no metallocene-metallocene interaction through the alkynyl-platinum bridges.