Subvalent group 13 molecules by carbene-induced hydrogen abstraction

Abstract

The N-Heterocyclic Carbene (NHC) alane and gallane adducts (NHC)∙Cp*AlH2 (NHC = Me2ImMe 5, iPr2ImMe 6, Dipp2Im 7) and (NHC)∙Cp*GaH2 (NHC = Me2ImMe 8, iPr2ImMe 9, Dipp2Im 10; R2Im = 1,3‐di-organyl-imidazolin-2-ylidene;...

NHC‐Adducts of Cyclopentadienyl‐Substituted Alanes

“…The compounds 5-7 show the expected NHC resonances in their 1 H and 13 C{ 1 H} NMR spectra, comparable to the corresponding unsubstituted or mono-iodide adducts respectively. [10,[20][21] The signals in the 27 Al{ 1 H} NMR spectra of 5-7 were found at δ = 88.1 ppm (5), 87.9 ppm (6), and 88.2 ppm (7), and therefore in a significantly different region compared to the resonances of the parent hydrides (NHC) • AlH 3 (δ = 106.3-107.8 ppm) and the mono-iodo alanes (NHC) • AlH 2 I 1-3 (δ = 107.8-109.6 ppm).…”

“…Similarly, the resonances of the coordinated NHC carbene carbon atoms in the 13 C{ 1 H} NMR spectra of the compounds 9 and 12 were detected at 165.1 (9) and 176.3 (10) ppm, clearly shifted from the corresponding signals of the starting material at 160.8 (1) and 169.6 (4) ppm. The carbon atoms of the Cp substituent give rise to one signal in the 13 C{ 1 H} NMR spectra located at 112.0 (9), 112.4 (10), 112.3 (11), and 112.0 (12) ppm, which also reflects the fast rearrangement of the Cp substituent on the NMR time scale.…”

“…Formation of 13-16 was confirmed by 1 H, 13 C{ 1 H}, 27 Al{ 1 H} NMR spectroscopy, IR-spectroscopy, and elemental analysis. The identity of the NHC-stabilized alane (Me 2 Im Me ) • AlHCp 2 13 was further confirmed by its solid-state structure (Figure 5).…”

“…We observed similar behavior for (NHC) • Cp*GaH 2 in solution at elevated temperatures previously. [13] 1 H and 27 Al NMR spectra were performed in a temperature range from 178 K to 353 K for (iPr 2 Im Me ) • AlH 2 Cp 10 to investigate the temperature dependence of this equilibrium (see Figures SI16 to SI19 of the Supporting Information). However, no significant shift of the equilibrium was observed in this temperature range.…”

“…[12] We also reported recently compounds of the type (NHC) • EH 2 Cp* IX (Cp* = C 5 Me 5 , E = Al, Ga; see Figure 1) and demonstrated that synthesis of subvalent group 13 molecules is feasible by carbene hydrogen abstraction starting from these simple molecules. [13] This brief survey on NHC-stabilized mixed aluminum organyl hydrides reveals that the chemistry of such compounds is nearly unexplored. The few compounds known are typically equipped with sterically demanding substituents at aluminum.…”