Synthesis and Reactivity Studies of Amido-Substituted Germanium(I)/Tin(I) Dimers and Clusters

Three amide ligands of varying steric bulk and electronic properties were utilized to prepare a series of amido-germanium(II)/tin(II) halide compounds, (LEX)_n, (L= -N{B(DipNCH)₂}(SiMe₃), ^TBoL; -N{B(DipNCH)₂}(SiPh₃), ^PhBoL; -N(Dip)(tBu), ^DBuL; Dip=C₆H₃iPr₂-2,6; E=Ge or Sn; X=Cl or Br; n=1 or 2). Reductions of these with a magnesium(I) dimer, {(^MesNacnac)Mg}₂ (^MesNacnac=[(MesNCMe)₂CH]⁻, Mes=mesityl), afforded singly bonded amido-digermynes (^TBoLGe−Ge^TBoL and ^PhBoLGe−Ge^PhBoL), and an amido-distannyne (^PhBoLSn−Sn^PhBoL), in addition to several low-valent, amido stabilized tetrel–tetrel bonded cluster compounds, (^DBuLGe)₄, (^DBuLSn)₆ and Sn₅(^TBoL)₄. The nature of the products resulting from these reactions was largely dependent on the steric bulk of the amide ligand employed. Cluster (^DBuLGe)₄ possessed an unusual folded butterfly structure, the bonding and electronic of which were examined using DFT calculations. Reactions of the amido-germanium(I) compounds with H₂ were explored, and gave rise to the amido-digermene, ^TBoL(H)Ge=Ge(H)^TBoL and the cyclotetragermane, {^DBuL(H)Ge}₄. Reactions of (^DBuLGe)₄ with a series of unsaturated small molecule substrates yielded ^DBuLGeOGe^DBuL, ^DBuLGe(μ-C₂H₄)₂Ge^DBuL and ^DBuLGe(μ-1,4-C₆H₈)(μ-1,2-C₆H₈)Ge^DBuL. The latter results imply that (^DBuLGe)₄ can act as a masked source of the digermyne ^DBuLGeGe^DBuL in these reactions. All further reactivity studies indicated that the germanium(I) compounds exhibit a “transition-metal-like” behavior, which is closely related to that previously described for bulky digermynes and related compounds.