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 κ(2) complexes of the type [M(CO)4 (κ(2)-H3 E⋅NHC)] with [M(CO)4 (COD)] (M=Cr, Mo), including the first κ(2) 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 κ(1) and κ(2) complexes were isolated, while [Cr(CO)4 (κ(2)-H2 Ga{(NDippCMe)2 CH})] is the only simple κ(2) 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)2 CH})]. Reaction of [Co2 (CO)8] with {HC(MeCDippN)2 }AlH2 generates [(OC)3 Co(μ-H)2 Al{(NdippCme)2 CH}][Co(CO)4] (12), which while retaining direct AlH interactions, features a hitherto unprecedented degree of bond activation in a σ-alane complex.