Pnictogen Bonding at the Core of a Carbene-Stiborane-Gold Complex: Impact on Structure and Reactivity

Our interest in the design of ambiphilic ligands and
their coordination
to gold has led us to synthesize an indazol-3-ylidene gold
chloride complex functionalized at the 4-position of the indazole
backbone by a stibine functionality. The antimony center of this new
complex cleanly reacts with o-chloranil to afford
the corresponding stiborane derivative. Structural analysis indicates
that the stiborane coordination environment is best described as a
distorted square pyramid whose open face is oriented toward the gold
center, allowing for the formation of a long donor–acceptor,
or pnictogen, Au → Sb bonding interaction. The presence of
this interaction, which has been probed computationally, is also manifested
in the enhanced catalytic activity of this complex in the cyclization
of N-propargyl-4-fluorobenzamide.