Cationic Bis(Gold) Indenyl Complexes

Abstract

AbstractReaction of (P)AuOTf [P=P(t‐Bu)2o‐biphenyl] with indenyl‐ or 3‐methylindenyl lithium led to isolation of gold η1‐indenyl complexes (P)Au(η1‐inden‐1‐yl) (1 a) and (P)Au(η1‐3‐methylinden‐1‐yl) (1 b), respectively, in >65 % yield. Whereas complex 1 b is static, complex 1 a undergoes facile, degenerate 1,3‐migration of gold about the indenyl ligand (ΔG≠153K=9.1±1.1 kcal/mol). Treatment of complexes 1 a and 1 b with (P)AuNTf2 led to formation of the corresponding cationic bis(gold) indenyl complexes trans‐[(P)Au]2(η1,η1‐inden‐1,3‐yl) (2 a) and trans‐[(P)Au]2(η1,η2‐3‐methylinden‐1‐yl) (2 b), respectively, which were characterized spectroscopically and modeled computationally. Despite the absence of aurophilic stabilization in complexes 2 a and 2 b, the binding affinity of mono(gold) complex 1 a toward exogenous (P)Au+ exceed that of free indene by ~350‐fold and similarly the binding affinity of 1 b toward exogenous (P)Au+ exceed that of 3‐methylindene by ~50‐fold. The energy barrier for protodeauration of bis(gold) indenyl complex 2 a with HOAc was ≥8 kcal/mol higher than for protodeauration of mono(gold) complex 1 a.