Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

With the 30 years old first example of a stable group 4 metallocene bis(trimethylsilyl)acetylene (btmsa) complex Cp2Ti(eta(2)-btmsa) a series of similar complexes like Cp ' M-2(eta(2)-btmsa) (M = Ti, Zr; Cp ' = Cp, Cp* as eta(5)-pentamethylcyclopentadienyl and Cp '(2) = rac-(ebthi) as rac-1,2-ethylene-1,1 '-bis(eta(5)-tetrahydroindenyl) ) represent excellent sources for the generation of the very reactive coordinatively and electronically unsaturated complex fragments [Cp'M-2], which were used in many synthetic and catalytic reactions. Examples for this were oresented in several papers and summarized in some reviews. In this update new reactions of group 4 metallocene bis(trimethylsilyl)acetylene complexes towards symmetrically and unsymmetrically alpha-dihetero-substituted alkynes, reactions with other alkynes, di- and polyynes to metallacyclopentadienes as well as the conversions of the formed products are summarized. Additionally, novel synthetic applications of the formed metallacyclopentadienes on the basis of the zirconocene bis(trimethylsilyl)acetylene complex Cp2Zr(py)(eta(2)-btmsa) are highlighted. Reactions with imines, neutral N-donor ligands, E-H compounds (E = N, O, P), molecular hydrogen, water, phosphino- and aminoboranes, E-Cl compounds (E = C, P), disilylated germylenes and aryloxy ketones were described. Different self-assembly reactions to multinuclear complexes by using group 4 metallocene bis(trimethylsilyl)acetylene complexes in C-C coupling reactions with or without C-H bond activation to tri- or tetranuclear complexes are considered, too. These examples are discussed following the general L-M-S principle for stoichiometric and catalytic reactions, whereby different ligands L (L = Cp ' = Cp, Cp*, rac-ebthi), metals M (M = Ti, Zr, Hf) and substrate substituents S influence the reactivity and the obtained products.