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

Abstract

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.

Frustrated Lewis Pair Chelation as a Vehicle for Low‐Temperature Semiconductor Element and Polymer Deposition

“…Oxidation of deposited Ge is likely due to brief exposure to air during sample transfer. [19] Raman spectroscopy confirmed the presence of amorphous Si and Ge, with broad Si-Si (485 cm À1 ) and Ge-Ge (280 cm À1 ) peaks present ( Figures S26 and S27). [9] Our strategy also enables the formation of FLP-diorganosilylene complexes, as demonstrated by the synthesis of [PB{SiMe 2 }] (5) (Figure 3 a) in a 70 % yield from the reaction between 3 and two equiv of MeLi.…”

“…[8]: 2: Ge1-P1 2.3447(3), Ge1-B1 2.1490- (15), Ge1-H1A 1.49(2), Ge1-H1B 1.58(2); P1-Ge1-B1 92.32 4, H1A-Ge1-H1B 102.99 (11). 4: Si-P 2.2787 5, Si-B 2.0769 15, Si-H1SI 1.414 (19), Si-H2SI 1.415 (19); P-Si-B 94.09 4, H1SI-Si-H2SI 102.9-(11). [9] Angewandte Chemie…”

Frustrated Lewis Pair Chelation as a Vehicle for Low‐Temperature Semiconductor Element and Polymer Deposition

“…The oxidation state of the deposited Si and Ge was probed using XPS, which showed one Si 0 environment for the Si films (Figure 2 c), while both Ge 0 and Ge II environments were identified for the Ge films (Figure S23) [9] . Oxidation of deposited Ge is likely due to brief exposure to air during sample transfer [19] . Raman spectroscopy confirmed the presence of amorphous Si and Ge, with broad Si‐Si (485 cm −1 ) and Ge‐Ge (280 cm −1 ) peaks present (Figures S26 and S27) [9]…”

“…Related data for deposited Ge can be found in the Supporting Information. [8]: Si1-P1 2.3055(6), Si1-B1 2.0746 (17), Si1-C1 1.890(2), Si1-C2 1.8902 (19); P1-Si1-B1 93.63 (5), C1-Si1-C2 104.21(10); [9] c) Photograph of deposited crude [SiMe 2 ] n in C 6 D 6 after heating 5 in toluene at 110 8C for 15 h.…”

“…[8]: 2: Ge1-P1 2.3447(3), Ge1-B1 2.1490- (15), Ge1-H1A 1.49(2), Ge1-H1B 1.58(2); P1-Ge1-B1 92.32 4, H1A-Ge1-H1B 102.99 (11). 4: Si-P 2.2787 5, Si-B 2.0769 15, Si-H1SI 1.414 (19), Si-H2SI 1.415 (19); P-Si-B 94.09 4, H1SI-Si-H2SI 102.9-(11). [9] Angewandte Chemie Zuschriften Oxidation of deposited Ge is likely due to brief exposure to air during sample transfer.…”