Coordination and activation of Al-H and Ga-H bonds

Abstract

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 k2 complexes of the type [M(CO)4(k2-H3E·NHC)] with [M(CO)4(COD)] (M = Cr, Mo), including the first k2 s-gallane complexes. b-Di-ketiminato ('nacnac')-stabilized systems, {HC(MeCNDip-p)2}EH2, show more diverse reactivity towards Group 6 car-bonyl reagents. For {HC(MeCNDipp)2}AlH2, both k1 and k2 complexes were isolated, while [Cr(CO)4(k2-H2Ga-{(NDippCMe)2CH})] is the only simple k2 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(m-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 s-alane complex.