Nucleophilic Degradation of a β-Diketiminato Ancillary by a Transient Scandium Hydride Intermediate

Reactions of a β-diketiminato-supported scandium dichloride LScCl2 (L = (Ar)NC(tBu)CHC(tBu)N(Ar); Ar = 2,6-iPr2-C6H3) with boro- and aluminohydride reagents result in transient scandium hydrides, which undergo hydride transfer to the ligand backbone, inducing fragmentation of the ancillary. The products of this fragmentation have been characterized and include an organic enamine (2) and scandium imido containing clusters. One such product, formed via reaction with LiBEt3H and LScCl2, is the trimer [ArNScCl(THF)]3[LiH(THF)], 1, which includes an occluded molecule of lithium hydride. The reactions involving LiAlH4, along with labeling studies, helped to clarify the fragmentation pathway and account for the observed products.