Activation of an Au−Cl Bond by a Pendent SbIII Lewis Acid: Impact on Structure and Catalytic Activity
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With the objective of identifying new coordination modes of ambiphilic ligands, we have investigated the bidentate Sb/P ligands (o-(Ph2 P)C6 H4 )SbCl2 (LCl ) and (o-(Ph2 P)C6 H4 )SbPh2 (LPh ). Reaction of these ligands with (tht)AuCl affords the monoligated species LCl AuCl (1) and LPh AuCl (2), respectively, in which the antimony centers are only weakly engaged with the coordinated gold atom. Treatment of 1 with PPh3 induces an intramolecular transfer of a chloride ligand from gold to antimony to form the zwitterionic species o-(Cl3 Sb)C6 H4 (Ph2 P)Au(PPh3 ) (3). Natural bond orbital (NBO) calculations show that the antimony and gold centers are involved in weak Sb→Au and Au→Sb interactions, the latter reflecting the Lewis acidity of the pendent antimony group. Finally, we demonstrate that the ability of the antimony center in 1 to abstract a gold-bound chloride in the presence of a Lewis basic substrate may be utilized to activate the gold center for the electrophilic cycloisomerization of propargylic amides.
author list (cited authors)
Jones, J. S., & Gabbai, F. P.