The Parent GaH2SbH2 Monomer Stabilized by an N-Heterocyclic Carbene

Abstract

The synthesis and characterization of the stibanyltrielanes IDipp·GaH₂Sb(SiMe₃)₂ (1a) and IDipp·BH₂Sb(SiMe₃)₂ (1b) are presented. 1a represents the first example for the isolation of a molecular stibanylgallane monomer stabilized only by a Lewis base (LB). While methanolytic cleavage of the {SiMe₃} residues in 1a cannot be achieved, the direct salt metathesis reactions of K(18c6)SbH₂ with LB·EH₂X (LB = IDipp, NMe₃; E = B, Ga; X = I, OTf) afford the isolation of the parent compounds IDipp·BH₂SbH₂ (2a), Me₃N·BH₂SbH₂ (2b), and IDipp·GaH₂SbH₂ (3) for the first time in moderate yields. Specifically, the synthesis of 3 not only represents the first stabilization of the {GaH₂SbH₂} motif as the so far heaviest known ethylene-like parent group 13/15 element combination but also validates its stabilization procedure by a LB to access a first sterically unhindered primary stibane. All compounds display drastic sensitivity toward air, light, and temperature. The products are characterized by NMR and infrared spectroscopy, as well as by single-crystal X-ray structure determination and mass spectrometry and the electronic structure is investigated by density functional theory calculations. Furthermore, the reaction of IDipp·GaCl₃ with K(18c6)SbH₂ yields a product mixture, in which 3 and the unprecedented IDipp·GaH(SbH₂)₂ (4) can be identified.