Synthesis and reactivity of a germylene stabilized by a boraguanidinate ligand

Abstract

The germylene [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge (1) was easily accessible by the reaction of the in situ prepared dilithium precursor [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Li₂ with GeCl₂·dioxane complex. The bonding situation in 1 has been also described from the theoretical point of view. This germylene is smoothly oxidized by diphenyldichalcogenides PhEEPh, I₂ or MeI to produce bis(phenylchalcogenato)germanes [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge(EPh)₂ [where E = S (2), Se (3) and Te (4)] and corresponding iodo-derivatives [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]GeI₂ (5) and [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge(Me)I (6). The treatment of 1 with bromine resulted in the unexpected formation of a heteroleptic germylene compound [(i-Pr)₂NB(NH-2,6-Me₂C₆H₃)(N-2,6-Me₂C₆H₃)]GeBr (7) and a germanium(IV) compound [(i-Pr)₂NB(NH-2,6-Me₂C₆H₃)(N-2,6-Me₂C₆H₃)]GeBr₃ (8). The reaction of germylene 1 with 2,3-dimethylbutadiene and 2,3-dibenzylbutadiene resulted in spiro-compounds [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge[CH₂C(R)C(R)CH₂] [where R = Me (10) and benzyl (11)]. Similarly, compound [(i-Pr)₂NB(N-2,6-Me₂C₆H₃)₂]Ge[N(Dip)CHCHN(Dip)] (12) (where Dip = 2,6-i-Pr₂C₆H₃) was obtained by the reaction of 1 with corresponding diimine (Dip)NCHCHN(Dip). All compounds were characterized by multinuclear NMR spectroscopy and their molecular structures were unambiguously established using single-crystal X-ray diffraction analysis.