Dedicated to Professor Hubert Schmidbaur on the occasion of his 70th birthday
Recently, we reported the preparation of the unique monomeric [LAl(SH) 2 ] (1) (L= HC(CMeNAr) 2 ; Ar= 2,6-iPr 2 C 6 H 3 ) comprising two terminal SH moieties. [1] This unusual species led us to explore the substitution pattern of the SH protons, their exchange with transition metals would open a new route for the preparation of heterobimetallic sulfides containing aluminum. To date very few examples with aluminum bridging sulfide are known. Such species include [(tBuAl)(tBuAlMe) 2 (m 3 -S) 3 ZrCp 2 ] (Cp = C 5 H 5 ), prepared by degradation of the [{tBuAl(m 3 -S)} 4 ] cage with two equivalents of [Cp 2 ZrMe 2 ]. [2] Moreover, there are known aluminum sulfides with [AlS] n core, which can be either planar (n = 2), cubic (n = 4), drum (n = 6), or possess more complex structures with an Al:S molar ratio different from 1:1. [3] Attempts to prepare heterobimetallic sulfides with 1 and ZnMe 2 or CdMe 2 through alkane elimination failed, in spite of the high affinity of these elements towards chalcogens. [4] We observed even at low temperature only the formation of an inseparable mixture of products and the free ligand. This situation is in contrast to the successful preparation of [LAl(m-S) 2 AlL] from 1 and [LAlH 2 ]. [3] Following the protocol of Nöth et al. on the preparation of aluminum-lithium salts from LiAlH 4 and thiols, [5] we chose the lithiation of 1 with MeLi and nBuLi in diethyl ether or THF as an alternative route to the desired compounds. Unfortunately, under the given conditions the decomposition of 1 was observed. However, the difficulties encountered in the preparation of the dilithium salt [{LAl[(SLi) 2 (thf) 3 ]} 2 ]•2 THF (2) were overcome by direct reaction of 1 with two equivalents of LiN(SiMe 3 ) 2 in THF at 0 8C. The extremely sensitive pale yellow product 2 is a dimer solvated by eight molecules of THF as demonstrated by X-ray structural analysis. It has low solubility in THF and forms a microcrystalline precipitate within a few seconds of starting materials being mixed. The recovery of the crystals