Activation of elemental sulfur by aluminum dihydride: isolation of mono- and bis(hydrogensulfide) complexes of aluminum.

The conversions of the dimeric imidazolin-2-iminato aluminum dihydride {μ-L(Dipp)AlH2}2 (1) with ¼ or ½ equivalents of S8 gave the elusive hydrogensulfide {μ-L(Dipp)Al(H)SH}2 (2) and the bisthiol {μ-L(Dipp)Al(SH)2}2 (3), respectively (L(Dipp)=NC(N(Dipp)CH)2, Dipp=2,6-diisopropylphenyl). Notably, these transformations proceeded in the absence of a promoter. The reaction of {μ-L(Mes)AlH2}2 (4), a less bulky congener of 1, with phenyl disulfide produces the phenyl sulfide {μ-L(Mes)Al(H)SPh}2 (5; L(Mes)=NC(N(Mes)CH)2, Mes=2,4,6-trimethylphenyl). The hitherto unknown compounds 2-5 were characterized by using spectroscopic methods and single-crystal X-ray diffraction analysis.