Potential sources of the electronic materials GaP and AlAs. Synthesis and X-ray structures of [ t-Bu 2 Ga(μ-(C 5H 9)PH)] 2 and [Et 2Al(μ- t-Bu 2As)] 2 (C 5H 9 = cyclopentyl)

Abstract

Reaction of GaCl 3 with t-BuLi (2 equiv.)and Li-(C 5H 9)PH in THF at −78°C gives colourless crystalline [ t-Bu 2Ga(μ-(C 5H 9)PH)] 2 ( 1) in 80% yield (C 5H 9 = cyclopentyl). Reaction of Et 3Al with t-Bu 2AsH at 220°C gives the aluminium arsenide dimer, [Et 2Al(μ- t-Bu 2As)] 2 ( 2) (63%). The X-ray structures of both ( 1) and ( 2) have been determined. They are both dimeric with bridging phosphido or arsenido groups and terminal alkyls. The coordination geometry of the Ga or Al atoms is roughly tetrahedral in each case. For compound ( 1) 31P NMR data indicate the presence of both the syn and anti isomers in solution (relative ratios 1:2.5). In the solid state only the anti isomer is observed. Crystal data for ( 1): C 26H 56Ga 2P 2, M = 570.12, monoclinic, C2/ m (No. 12), a = 16.736(3), b = 11.586(1), c = 8.413(2) Å, β = 104.62(1)°, U = 1578.6(5) Å 3, D c = 1.20 g cm −3, Z = 2, μ(Mo- K α ) = 18.11 cm −1. Refinement of 1054 reflections ( I 3σ( I)) out of 1447 unique observed reflections (3° ⩽ 2θ ⩽ 50°) gave RR w values of 0.0503 and 0.0565, respectively. Data/parameter ratio = 12.85, highest peak in final difference Fourier = 0.604 e Å −3. Crystal data for ( 2): C 24H 56Al 2As 2, M = 434.29, monoclinic, P2 1/ n (No. 14), a = 8.907(1), b = 11.691(1), c = 14.735(3) Å, β = 90.25(1)°, U = 1534.4(5) Å 3, D c = 1.88 g cm −3, Z = 4, μ(Mo- K α) = 44.47 cm −1. Refinement of 1165 reflections ( I > 3σ( I)) out of 2700 unique observed reflections (3° ⩽ 2θ; ⩽ 50°) gave R and R w values of 0.0523 and 0.0600, respectively. Data/parameter ratio = 9.173, highest peak in the final difference Fourier = 0.439 e Å −3.