Synthesis and structural characterization of two-coordinate low-valent 14-group metal complexes bearing bulky bis(amido)silane ligands

Abstract

A series of germylene, stannylene and plumbylene complexes [η²(N,N)-Me₂Si(DippN)₂Ge:] (3a), [η²(N,N)-Ph₂Si(DippN)₂Ge:] (3b), [η²(N,N)-Me₂Si(DippN)₂Sn:] (4), [η²(N,N)-Me₂Si(DippN)₂Pb:]₂ (5a), and [η²(N,N)-Ph₂Si(DippN)₂Pb:] (5b) (Dipp = 2,6-iPr₂C₆H₃) bearing bulky bis(amido)silane ligands were readily prepared either by the transamination of M[N(SiMe₃)₂]₂ (M = Sn, Pb) and [Me₂Si(DippNH)₂] or by the metathesis reaction of bislithium bis(amido)silane [η¹(N),η¹(N)-R₂Si(DippNLi)₂] (R = Me, Ph) with the corresponding metal halides GeCl₂(dioxane), SnCl₂, and PbCl₂, respectively. Preliminary atom-transfer chemistry involving [η²(N,N)-Me₂Si(DippN)₂Ge:] (3a) with oxygen yielded a dimeric oxo-bridged germanium complex [η²(N,N)-Me₂Si(DippN)₂Ge(μ-O)]₂ (6). All complexes were characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, IR, and elemental analysis. X-ray single crystal diffraction analysis revealed that the metal centres in 3b, 4, and 5b are sterically protected to prevent interaction between the metal centre and the nitrogen donors of adjacent molecules while complex 5a shows a dimeric feature with a strong intermolecular Pb⋯N interaction.