Activation of M–Cl Bonds with Phosphine–Alanes: Preparation and Characterization of Zwitterionic Gold and Copper Complexes

The
triphosphine–alane [iPr2P­(o-C6H4)]3Al (1) was prepared by coupling ortho-lithiated diisopropylphenylphosphine
with AlCl3. Reactions of 1 with gold and copper
chlorides afforded the zwitterionic cage complexes 2 and 3. The three phosphine arms coordinate symmetrically to the
coinage metal, while the aluminum center abstracts the chloride. Coordination
of the related diphosphine–alane [iPr2P­(o-C6H4)]2AlCl (4) to CuCl is also accompanied by a shift of the
chloride atom from copper to aluminum. However, the ensuing highly
electrophilic Cu+ center engages in weak intra- and intermolecular
Cl→Cu interactions, resulting in the original polymeric complex 5. The structures of all complexes have been ascertained spectroscopically
and crystallographically, and their bonding situations have been analyzed
by DFT calculations.