Coordination Chemistry of Disilylated Germylenes with Group 4 Metallocenes.

Reaction of the PEt 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 CpTiCl did not give the expected germylene NHC titanocene complex. This complex was, however, obtained in the reaction of CpTi(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.