Stepwise Deprotonation of a Thiol-Functionalized Bis(1,2,4-triazolium) Salt as a Selective Route to Heterometallic NHC Cornplexes

Heterometallic NHC complexes have been selectively prepared at room temperature directly from an azolium salt in a two-step procedure. In the unsymmetrically substituted bis(1,2,4-triazolium) ligand precursor, one of the m-xylylene-bridged triazolium units features an unprotected o-thiophenol substituent. This renders possible a selective deprotonation and in situ monopalladation at the NHC thiolato unit. The obtained palladium(II) complex possesses two pendant triazolium units as vacant binding sites. After a second deprotonation/metalation step, a heterodinuclear palladium(II) gold(I) complex and a heterotrinuclear palladium(II) dicopper(I) complex were obtained. In the latter, two metal centers are connected via a thiolato bridge.