Unsymmetrical Disulfides and Thiol Mixtures Produce Different Mixed Monolayer-Protected Gold Clusters

Synthesis of mixed monolayer-protected Au clusters (MPCs) from unsymmetrical disulfides (HO(CH 2 ) 11 SS(CH 2 ) 11 CH 3 ) yields clusters with a 1:1 composition of HO(CH 2 ) 11 S− and CH 3 (CH 2 ) 11 S− thiolates, whereas products from reaction of a 1:1 mixture of thiols (HO(CH 2 ) 11 SH and CH 3 (CH 2 ) 11 SH) contain mostly (97%) HO(CH 2 ) 11 S− ligands in the monolayer. The results suggest a thermodynamically preferred ligation of HO(CH 2 ) 11 SH over CH 3 (CH 2 ) 11 SH that is circumvented in the disulfide reaction. The core sizes of MPCs synthesized from alkanethiol and dialkyl disulfides are similar, suggesting similar MPC growth dynamics for thiols and disulfides. The compositions of MPCs synthesized starting from gold(I)−thiolate polymer intermediates suggest that the polymer undergoes immediate breakup upon addition of reductant.