Coordination and Activation of AlH and GaH Bonds

The modes of interaction of donor‐stabilized Group 13 hydrides (E=Al, Ga) were investigated towards 14‐ and 16‐electron transition‐metal fragments. More electron‐rich N‐heterocyclic carbene‐stabilized alanes/gallanes of the type NHC?EH₃ (E=Al or Ga) exclusively generate κ² complexes of the type [M(CO)₄(κ²‐H₃E?NHC)] with [M(CO)₄(COD)] (M=Cr, Mo), including the first κ² σ‐gallane complexes. β‐Diketiminato (′nacnac′)‐stabilized systems, {HC(MeCNDipp)₂}EH₂, show more diverse reactivity towards Group 6 carbonyl reagents. For {HC(MeCNDipp)₂}AlH₂, both κ¹ and κ² complexes were isolated, while [Cr(CO)₄(κ²‐H₂Ga{(NDippCMe)₂CH})] is the only simple κ² adduct of the nacnac‐stabilized gallane which can be trapped, albeit as a co‐crystallite with the (dehydrogenated) gallylene system [Cr(CO)₅(Ga{(NDippCMe)₂CH})]. Reaction of [Co₂(CO)₈] with {HC(MeCDippN)₂}AlH₂ generates [(OC)₃Co(μ‐H)₂Al{(NdippCme)₂CH}][Co(CO)₄] ( 12 ), which while retaining direct Al?H interactions, features a hitherto unprecedented degree of bond activation in a σ‐alane complex.