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 ), ^TBo L; -N{B(DipNCH)₂ }(SiPh₃ ), ^PhBo L; -N(Dip)(tBu), ^DBu L; Dip=C₆ H₃ iPr₂ -2,6; E=Ge or Sn; X=Cl or Br; n=1 or 2). Reductions of these with a magnesium(I) dimer, {(^Mes Nacnac)Mg}₂ (^Mes Nacnac=[(MesNCMe)₂ CH]^- , Mes=mesityl), afforded singly bonded amido-digermynes (^TBo LGe-Ge^TBo L and ^PhBo LGe-Ge^PhBo L), and an amido-distannyne (^PhBo LSn-Sn^PhBo L), in addition to several low-valent, amido stabilized tetrel-tetrel bonded cluster compounds, (^DBu LGe)₄ , (^DBu LSn)₆ and Sn₅ (^TBo L)₄ . The nature of the products resulting from these reactions was largely dependent on the steric bulk of the amide ligand employed. Cluster (^DBu LGe)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, ^TBo L(H)Ge=Ge(H)^TBo L and the cyclotetragermane, {^DBu L(H)Ge}₄ . Reactions of (^DBu LGe)₄ with a series of unsaturated small molecule substrates yielded ^DBu LGeOGe^DBu L, ^DBu LGe(μ-C₂ H₄ )₂ Ge^DBu L and ^DBu LGe(μ-1,4-C₆ H₈ )(μ-1,2-C₆ H₈ )Ge^DBu L. The latter results imply that (^DBu LGe)₄ can act as a masked source of the digermyne ^DBu LGeGe^DBu L 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.