Synthesis and equilibrium binding studies of cationic, two-coordinate gold(I) π-alkyne complexes

Reaction of a 1:1 mixture of (L)AuCl [L = P(t-Bu)2o-biphenyl or IPr] and AgSbF6 with internal alkynes led to isolation of the corresponding cationic, two-coordinate gold π-alkyne complexes in ≥ 90% yield. Equilibrium binding studies show that the binding affinities of alkynes to gold(I) are strongly affected by the electron density of the alkyne and to a lesser extent on the steric bulk of the alkyne. These substituent effects on alkyne binding affinity are greater than are the differences between the inherent binding affinities of alkynes and alkenes to gold(I).