Simple Mercury-Free Synthesis and Characterization of Symmetric and Unsymmetric Mono- and Dialkynyl (tpy)Au(III) Complexes

A highly efficient mercury-free route, providing [C^N] cyclometalated symmetric dialkynyl gold­(III) complexes with 2-(p-tolyl)­pyridine (tpy) as bidentate ligands and using alkynyllithium reagents, was developed. With 1,9-decadiyne, an unprecedented representative of a di­(bidentate) gold­(III) complex, for the first time became accessible. By using Grignard instead of the alkynyllithium reagents, we succeeded in synthesizing a range of novel monoalkynyl gold­(III) complexes in excellent yields (74–92%) and diastereoselectivity. Treating [(tpy)­Au­(CCTMS)₂] with Bu₄NF in THF gave a complete deprotection, and with K₂CO₃ in methanol, there was a selective deprotection of the TMS group trans to the pyridyl N atom, providing [(tpy)­Au­(CCH)­(CCTMS)] as the major product. This new type of cyclometalated gold­(III) complex bears two different alkynes as ancillary ligands. The further functionalization of the monoalkynyl (tpy)­gold­(III) complexes was investigated, offering a universal unprecedented and diastereoselective access to unsymmetrical dialkynyl (tpy)­gold­(III) complexes.