Aluminum-Phosphorus Chemistry: Preparation and Structural Characterization of [Et2AlP(SiMe3)2]2, Et(Cl)2Al·P(SiMe3)3, and i-Bu2(Cl)Al·P(SiMe3)3

Reactions of R2AlCl (R = Et, i-Bu) and EtAlCl2 with P(SiMe3)3 and LiP(SiMe3)2 were studied to investigate the potential use of dehalosilylation and lithium chloride elimination reactions for the preparation of compounds containing either [formula omitted] or [formula omitted] core rings. The dimeric compound [Et2AlP(SiMe3)2]2 (1) was isolated from the 1:1 reaction of Et2AlCl and LiP(SiMe3)2 at −78 °C, as a result of LiCl elimination. The 1:1 reaction of EtAlCl2 and P(SiMe3)3 yields Et(Cl)2Al·P(SiMe3)3 (2). Interestingly, a similar reaction between Et2AlCl and P(SiMe3)3 in a 2:1 mole ratio also affords 2, in moderate yield, suggesting a rearrangement of the original aluminum alkyl halide. However, when Et2AlCl was reacted with P(SiMe3)3 in a 1:1 mole ratio, the expected adduct Et2(Cl)AlP(SiMe3)3 (3) results. Unlike the Et2AlCl reaction, the analogous 2:1 mole reaction of i-Bu2AlCl and P(SiMe3)3 forms the monochloro adduct, i-Bu2AlCl·P(SiMe3)3 (4), rather than a rearrangement product. Compounds 1–4 were characterized by partial elemental analysis, melting point data, as well as 1H, 13C, 31P, and 27Al NMR spectroscopy. Compounds 1, 2, and 4 were also characterized by single-crystal X-ray crystallography. Dimer 1 crystallizes in the monoclinic system, space group C2/c (C2h6), with unit cell dimensions of a = 18.085(2) Å, b = 9.452(1) Å, c = 20.233(2) Å, and β = 100.30(1)° for Z = 4. Crystals of adduct 2 have unit cell parameters of a = 13.234(2) Å, b = 13.147(2) Å, and c = 13.043(2) Å for Z = 4 and belong to the orthorhombic system, space group Pca21 (C2v5), while adduct 4 crystallizes in the monoclinic system, space group P21/c (C2h5), with cell dimensions of a = 14.986(3) Å, b = 11.489(2) Å, c = 18.570(4) Å, and β = 119.57 (2)°for Z = 4. © 1993, American Chemical Society. All rights reserved.

Duke Scholars

Author Andrew T. McPhail Chemistry