Titanium Germylidenes.

Two novel 18-electron titanium germylene complexes, Cp2 Ti(L)=Ge[Si3 (SiMet Bu2 )4 ] 3 b (L=Me3 P) and 3 c (L=XylNC), were synthesized, isolated, and structurally characterized. The length of the titanium-germanium bonds of 2.5387(3) Å and 2.5276(3) Å (in 3 b and 3 c, respectively) well match those expected for the double bond, which was further supported by the DFT study. Based on their structural characteristics, as well as their atomic charges calculations which revealed Ti(δ+)=Ge(δ-) bond polarization, both 3 b and 3 c are classified as the Schrock-type titanium germylidenes, as the germanium analogues of the widely known titanium alkylidenes. By contrast, germylene complexes of the group 6 metals 8 a (M=Mo) and 8 b (M=W) are better described as Fischer-type germylene complexes.