The coordination of an electron-donating ligand which is essential for the thermal stability of all the above zirconocene acetylene complexes can, in principle, be substituted by the electron-donation effect of methyl substituents at the cyclopentadienyl ligands. 11 Such an effect has been clearly demonstrated in the series of methylated titanocene monohalides (C 5 H 5 - n Me n ) 2 TiX (n = 0, 1, 3−5; X = Cl, Br, I) by the increasing reluctance to dimerize or to ...
