Coordination Chemistry of Disilylated Germylenes with Group 4 Metallocenes

Reaction
of the PEt3 adduct of a disilylated five-membered cyclic
germylene with group 4 metallocene dichlorides in the presence of
magnesium led to the formation of the respective germylene metallocene
phosphine complexes of titanium, zirconium, and hafnium. Attempts
to react the related NHC adduct of a disilylated four-membered cyclic
germylene under the same conditions with Cp2TiCl2 did not give the expected germylene NHC titanocene complex. This
complex was, however, obtained in the reaction of Cp2Ti­(btmsa)
with the NHC germylene adduct. A computational analysis of the structure
of the group 4 metallocene germylene complexes revealed the multiple-bond
character of the M–Ge­(II) linkage, which can be rationalized
with the classical σ-donor/π-acceptor interaction. The
strength of the M–Ge­(II) bond increases descending group 4.