Bidentate Phosphanyl- and Arsanylboranes

Insight into the Decomposition Mechanism of Donor-Acceptor Complexes of EH2 (E = Ge and Sn) and Access to Germanium Thin Films from Solution

Electron-donating N-heterocyclic carbenes (Lewis bases, LB) and electron-accepting Lewis acids (LA) have been used in tandem to yield donor-acceptor complexes of inorganic tetrelenes LB·EH₂·LA (E = Si, Ge, and Sn). Herein, we introduce the new germanium (II) dihydride adducts ImMe₂·GeH₂·BH₃ (ImMe₂ = (HCNMe)₂C:) and ImⁱPr₂Me₂·GeH₂·BH₃ (ImⁱPr₂Me₂ = (MeCNⁱPr)₂C:), with the former complex containing nearly 40 wt % germanium. The thermal release of bulk germanium from ImMe₂·GeH₂·BH₃ (and its deuterated isotopologue ImMe₂·GeD₂·BD₃) was examined in solution, and a combined kinetic and computational investigation was undertaken to probe the mechanism by which Ge is liberated. Moreover, the thermolysis of ImMe₂·GeH₂·BH₃ in solution cleanly affords conformal nanodimensional layers of germanium as thin films of variable thicknesses (20-70 nm) on silicon wafers. We also conducted a computational investigation into potential decomposition pathways for the germanium(II)- and tin(II)-dihydride complexes NHC·EH₂·BH₃ (NHC = [(HCNR)₂C:]; R = 2,6-ⁱPr₂C₆H₃ (Dipp), Me, and H; and E = Ge and Sn). Overall, this study introduces a mild and convenient solution-only protocol for the deposition of thin films of Ge, a widely used semiconductor in materials research and industry.

Monomeric β-Diketiminato Group 13 Metal Dipnictogenide Complexes with Two Terminal EH2 Groups (E=P, As)

The pnictogenyl Group 13 compounds (Dipp2 Nacnac)M[E(SiMe3 )2 ]Cl and (Dipp2 Nacnac)M(EH2 )2 (Dipp2 Nacnac=HC[C(Me)N(Ar)]2 , Ar: Dipp=2,6-iPr2 C6 H3 ; M=Al, Ga, In; E=P, As) were successfully synthesized. The salt metathesis between (Dipp2 Nacnac)MCl2 and LiE(SiMe3 )2 only led to monosubstituted compounds (Dipp2 Nacnac)M[E(SiMe3 )2 ]Cl [E=P, M=Ga(1), In (2); E=As, M=Ga (3), In (4)], regardless of the stoichiometric ratios used. In contrast to the steric effect of the SiMe3 groups in 1-4, the reactions of the corresponding halides with LiPH2 ⋅DME (or KAsH2 ) facilely yielded the dipnictogenide compounds (Dipp2 Nacnac)M(EH2 )2 (E=P, M=Al (5), Ga (6), In (7); E=As, M=Al (8), Ga (9)), avoiding the use of flammable and toxic PH3 and AsH3 for their synthesis. The compounds 5-9 are the first examples of monomeric Group 13 diphosphanides and diarsanides in which the metal center is bound to two terminal PH2 and AsH2 groups, respectively. In contrast to the successful synthesis of the indium diphosphanide (Dipp2 Nacnac)In(PH2 )2 , the reaction of (Dipp2 Nacnac)InCl2 with KAsH2 led to an indium mirror due to the instability of the target product.