Expanding the Steric Coverage Offered by Bis(amidosilyl) Chelates: Isolation of Low-Coordinate N-Heterocyclic Germylene Complexes

The synthesis and coordination chemistry of a series of dianionic bis(amido)silyl and bis(amido)disilyl, [NSiN] and [NSiSiN], chelates with N-bound aryl or sterically modified triarylsilyl (SiAr3) groups is reported. In order to provide a consistent comparison of the steric coverage afforded by each ligand construct, various two-coordinate N-heterocyclic germylene complexes featuring each ligand set were prepared and oxidative S-atom transfer chemistry was explored. In the cases where clean oxidation transpired, sulfido-bridged centrosymmetric germanium(IV) dimers of the general form [LGe(μ-S)]2 (L = bis(amidosilyl) ligands) were obtained in lieu of the target monomeric germanethiones with discrete GeS double bonds. These results indicate that the reported chelates possess sufficient conformational flexibility to allow for the dimerization of LGeS units to occur. Notably, the new triarylsilyl groups (4-RC6H4)3Si (R = t Bu and i Pr) still offer considerably expanded degrees of steric coverage relative to the parent congener, SiPh3, and thus the use of substituted triarylsilyl groups within ligand design strategies should be a generally useful concept in advancing low-coordination main group and transition-metal chemistry.