[As_2(AlCp*)_3]--A Compound with a Polyhedral As_2Al_3 Framework

摘要

Since the first report on the synthesis of [(Cp*Al)_4] (Cp* = pentamethylcyclopentadienyl, C_5Me_5), this versatile reagent has been used for the synthesis of new organoaluminum compounds. For example, reaction with selenium or tellurium provided heterocubane analogues, while that with P_4 led to a compound containing [P_4(AlCp*)_6] units. These do not have the expected adamantane-like structure with AlCp*-bridged P_4 tetrahedra; instead, they are made up of two face-sharing hete-rocubanes, each ofwhich lacks one phosphorus atom (see Fig. 2). Halving this molecule would lead to [P_2(AlCp*)_3], for which a trigonal-bipyramidal structure is expected. Although no geometric parameters could be obtained, a similar structure has been proposed by Roeskyet al. for the analogous [Sb2(AlCp*)3] on the basis of preliminary X-ray structure studies 141 We report here on the analogous arsenic compound [As_2(AlCp*)_3] (1), which, according to X-ray structure analysis, exists as a heteropolyhedron with a trigonal-bipyramidal structure (Fig. 1).