Cationic aza-macrocyclic complexes of germanium(ii) and silicon(iv)

Abstract

[GeCl₂(dioxane)] reacts with the neutral aza-macrocyclic ligands L, L = Me₃tacn (1,4,7-trimethyl-1,4,7-triazacyclononane), Me₄cyclen (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) or Me₄cyclam (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and two mol. equiv. of Me₃SiO₃SCF₃ in thf solution to yield the unusual and hydrolytically very sensitive [Ge(L)][O₃SCF₃]₂ as white solids in moderate yield. Using shorter reaction times [Ge(Me₃tacn)]Cl₂ and [Ge(Me₃tacn)]Cl[O₃SCF₃] were also isolated; the preparation of [Ge(Me₄cyclen)][GeCl₃]₂ is also described. The structures of the Me₃tacn complexes show κ³-coordination of the macrocycle, with the anions interacting only weakly to produce very distorted five- or six-coordination at germanium. In contrast, the structure of [Ge(Me₄cyclen)][O₃SCF₃]₂ shows no anion interactions, and a distorted square planar geometry at germanium from coordination to the tetra-aza macrocycle. Crystal structures of the Si(IV) complexes, [SiCl₃(Me₃tacn)]Y (Y = O₃SCF₃, BAr^F; [B{3,5-(CF₃)₂C₆H₃}₄]) and [SiHCl₂(Me₃tacn)][BAr^F], obtained from reaction of SiCl₄ or SiHCl₃ with Me₃tacn, followed by addition of either Me₃SiO₃SCF₃ or Na[BAr^F], contain distorted octahedral cations, with facial κ³-coordinated Me₃tacn. The open-chain triamine, Me₂NCH₂CH₂N(Me)CH₂CH₂NMe₂ (pmdta), forms [SiCl₃(pmdta)][BAr^F] and [SiBr₃(pmdta)][BAr^F] under similar conditions, containing mer-octahedral cations.