Phosphanylalanes and Phosphanylgallanes Stabilized only by a Lewis Base

Abstract

The synthesis and characterization of the first parent phosphanylalane and phosphanylgallane stabilized only by a Lewis base (LB) are reported. The corresponding substituted compounds, such as IDipp⋅GaH₂ PCy₂ (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) were obtained by the reaction of LiPCy₂ with IDipp⋅GaH₂ Cl. However, the LB-stabilized parent compounds IDipp⋅GaH₂ PH₂ (3) and IDipp⋅AlH₂ PH₂ (4) were prepared via a salt metathesis of LiPH₂ ⋅DME with IDipp⋅E'H₂ Cl (E'=Ga, Al) or by H₂ -elimination reactions of IDipp⋅E'H₃ (E'=Ga, Al) and PH₃ , respectively. The compounds could be isolated as crystalline solids and completely characterized. Supporting DFT computations gave insight into the reaction pathways as well as into the stability of these compounds with respect to their decomposition behavior.

Keywords: Lewis bases; alanes; gallanes; main-group elements; phosphorus.

Figure 1

Different types of stabilization of the parent compounds of the pentelyltrielanes.

Figure 2

Different oligomeric products of the reaction between PH₃⋅W(CO)₅ and AlH₃⋅NMe₃/AlH₃⋅NEt₃.

Figure 3

Molecular structure of 1 in the solid state. Selected bond lengths [Å] and angles [°]: Ga–P 2.3724(6), Ga–C1 2.090(2); H1‐Ga‐P‐C4 125.6, C1‐Ga‐P 112.34(5). See Supporting Information for crystallographic details and all CCDC numbers.

Figure 4

Molecular structure of 3 in the solid state. Selected bond lengths [Å] and angles [°]: Ga–P 2.3373(6), Ga–C1 2.0507(2); H1‐Ga‐P‐H3 164.1°, C1‐Ga‐P 109.19(5).

Figure 5

Molecular structure of 4 in the solid state. Selected bond lengths [Å] and angles [°]: Al–P 2.3131(10), Al−C1 2.056(2), C1‐Al‐P 113.17(7). The H atoms at the P atom were restrained at fixed positions.