A complete series of N-heterocyclic tetrylenes (Si-Pb) with a 1,1'-ferrocenediyl backbone enabled by 1,3,2-diazaborolyl N -substituents.

The use of bulky 1,3,2-diazaborolyl N -substituents has allowed the synthesis of the complete series of ferrocene-based N-heterocyclic tetrylenes fc[(N{B}) 2 E] (fc = 1,1'-ferrocenediyl, {B} = (HCNC 6 H 3 -2,6- i Pr 2 ) 2 B, E = Si-Pb). The silylene fc[(N{B}) 2 Si] is inert towards NH 3 , CO 2 or N 2 O under ambient conditions and thus significantly less reactive than the N -aryl homologue fc[(NC 6 H 3 -2,6- i Pr 2 ) 2 Si]. In accord with its higher reactivity, computational results indicate a more pronounced ambiphilicity of fc[(NC 6 H 3 -2,6- i Pr 2 ) 2 Si]. Our computational investigation of the model compound fc[(NBMe 2 ) 2 Si] suggests that silylenes of this type may be superior to fc[(NC 6 H 3 -2,6- i Pr 2 ) 2 Si] in terms of ambiphilicity.