Experimental and Theoretical Studies of Unusual Four‐Membered Metallacycles from Reactions of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes with the Sulfurdiimide Me 3 SiN=S=NSiMe 3

The use of the sulfurdiimide RN=S=NR′ (R = R′ = SiMe 3 , 3 ) in reactions with group 4 metallocene bis(trimethylsilyl)acetylene complexes of the type [Cp 2 M(L)(η 2 ‐Me 3 SiC 2 SiMe 3 )] ( 1 : M = Ti, no L; 2 : M = Zr, L = pyridine) has led to the formation of four‐membered metallacycles 4M containing the group 4 metal, nitrogen and sulfur. DFT calculations performed on compound 4Ti indicate that this complex is best described as a σ‐complex with cyclic delocalisation of the ring electrons. Moreover, pseudo‐Jahn–Teller distortion plays a significant role in stabilising this complex.