Activation of an Au−Cl Bond by a Pendent Sb^III Lewis Acid: Impact on Structure and Catalytic Activity

Abstract

With the objective of identifying new coordination modes of ambiphilic ligands, we have investigated the bidentate Sb/P ligands (o-(Ph P)C H )SbCl (L ) and (o-(Ph P)C H )SbPh (L ). Reaction of these ligands with (tht)AuCl affords the monoligated species L AuCl (1) and L AuCl (2), respectively, in which the antimony centers are only weakly engaged with the coordinated gold atom. Treatment of 1 with PPh induces an intramolecular transfer of a chloride ligand from gold to antimony to form the zwitterionic species o-(Cl Sb)C H (Ph P)Au(PPh ) (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.

Digging the Sigma‐Hole of Organoantimony Lewis Acids by Oxidation

“…Recent efforts in the chemistry of organoantimony(III) have established that derivatives such as I and II readily bind halide anions (Figure ) by donation into the σ* orbital (Figure ) . Based on the same principle, we also found that antimony(III) halides could serve to promote the activation of transition metals either by direct interaction with the metal ( III ) or anion abstraction ( IV ) (Figure ).…”

“…[1] Antimony derivatives,b ecause of their intrinsically higher Lewis acidity, [2] are also drawing considerable attention both in the areas of small-molecule activation and catalysis, [3] as well as in anion complexation. [7] Based on the same principle,w ea lso found that antimony(III) halides could serve to promote the activation of transition metals either by direct interaction with the metal (III) [8] or anion abstraction (IV) [9] (Figure 1). [7] Based on the same principle,w ea lso found that antimony(III) halides could serve to promote the activation of transition metals either by direct interaction with the metal (III) [8] or anion abstraction (IV) [9] (Figure 1).…”

Digging the Sigma‐Hole of Organoantimony Lewis Acids by Oxidation

“…[4] Recent efforts in the chemistry of organoantimony(III) [5] have established that derivatives such as I [6] and II [7] readily bind halide anions ( Figure 1) by donation into the s*orbital (Figure 2). [7] Based on the same principle,w ea lso found that antimony(III) halides could serve to promote the activation of transition metals either by direct interaction with the metal (III) [8] or anion abstraction (IV) [9] (Figure 1).…”

Structural Evidence for Pnictogen-Centered Lewis Acidity in Cationic Platinum-Stibine Complexes Featuring Pendent Amino or Ammonium Groups

“…Although a parallel is often drawn with the ubiquitous phosphine ligands, stibines display several atypical traits and can, for example, undergo redox reactions without dissociation of the coordinated metal [5][6][7][8][9][10]. Moreover, while phosphines mostly act as two-electron donor spectator ligands, stibines have been shown to display Lewis acidic properties, even when coordinated to a transition metal [11][12][13][14][15][16][17][18][19][20][21][22]. These Lewis acidic properties manifest in the formation of long contacts between the antimony center of cationic complexes and counteranions as in complex [A] + which was isolated by Reid (Figure 1) [11].…”