Synthesis and characterization of novel aluminum-arsenic compounds. Crystal structure of [Et2AlAs(SiMe3)2]2

The viability of dehalosilylation and lithium chloride elimination reactions for use in the preparation of compounds containing core rings of the type was investigated. The second fully characterized aluminum-arsenic dimer, Et2AlAs(SiMe3)22, was isolated from a coupling reaction between Et2Alcl and LiAs(SiMe3)3 carried out at -78 C. Dehalosilylation reaction between Et2AlCl and As(SiMe3)3 in 1:1 and 2:1 mole ratios at ambient temperature failed to give the expected products, instead yielding the adduct Et2(Cl)Al As(SiMe3)3 (2). As evidenced by 1H NMR spectra, an NMR tube sample of 2 in benzene-d6 did undergo internal dehalosilylation when heated to 87 C in an oil bath. X-ray crystallographic analysis of 1 confirms its dimeric solid state structure and shows the Al-As-Al-As ring to be planar. Compound 1 crystallizes in the monoclinic system, space group C2/c (C2h6), with four molecules in a unit cell.