Coordination and Activation of EH Bonds (E=B, Al, Ga) at Transition Metal Centers

Magnesium, zinc, aluminium and gallium hydride complexes of the transition metals

“…Aldridge and co-workers pioneered this area of research and have isolated a series of σ-alane and σ-gallane complexes of groups 6 and 7 transition metal carbonyls. 31 – 35 Like 2 and 3 , the structures of 4–7 contain σ-Al–H adducts and derive from ligand exchange reactions, in this case from the parent metal carbonyl under either thermal or photochemical conditions. Four-electron, η 2 :η 2 -coordination of H–Al–H ( 8 – 9 ) requires a 14-electron transition metal fragment, {M(CO) 4 } and necessitates displacement of two ligands from ML 6 starting materials.…”

Supported σ‐Complexes of Li−C Bonds from Coordination of Monomeric Molecules of LiCH3, LiCH2CH3 and LiC6H5 to Mo≣Mo Bonds

“…Computational studies disclose the existence of five-center six-electron bonding within the HÀ Mo� � MoÀ CÀ Li metallacycles, with a mostly covalent HÀ Mo� � MoÀ C group and predominantly ionic LiÀ C and LiÀ H interactions. However, the latter bonds exhibit non-negligible covalency, as indicated by X-ray, computational data and the large one-bond 6,7 Li, 1 H and 6,7 Li, 13 C NMR coupling constants found for the three-atom HÀ LiÀ C chains. By contrast, the phenyl group in 4•LiC 6 H 5 coordinates in an η 2 fashion to the lithium atom through the ipso and one of the ortho carbon atoms.…”

“…[2][3][4][5] At that time, the nature of the NiÀ XÀ E bridging bond was not ascertained, but nowadays it is widely accepted that the Ni(μ-H)Al complex reported by Pörschke et al in 1990, [5] evidenced for the first time unsupported alane coordination. [6] The study of intermolecular complexes of transition metals and main-group metals like Mg, Al, Ga or Zn EÀ H bonds, has recently emerged as a principal focus of research, because these compounds constitute key intermediates in bond activation reactions. [6,7] Information on analogous complexes of EÀ C bonds is, nevertheless, sparse, although a few compounds presumably containing coordinated EÀ C bonds have been reported.…”

Supported σ‐Complexes of Li−C Bonds from Coordination of Monomeric Molecules of LiCH3, LiCH2CH3 and LiC6H5 to Mo≣Mo Bonds

“…At that time, the nature of the Ni−X−E bridging bond was not ascertained, but nowadays it is widely accepted that the Ni(μ‐H)Al complex reported by Pörschke et al. in 1990, [5] evidenced for the first time unsupported alane coordination [6] …”

“…The study of intermolecular complexes of transition metals and main‐group metals like Mg, Al, Ga or Zn E−H bonds, has recently emerged as a principal focus of research, because these compounds constitute key intermediates in bond activation reactions [6,7] . Information on analogous complexes of E−C bonds is, nevertheless, sparse, although a few compounds presumably containing coordinated E−C bonds have been reported [2–4,8–17] .…”