Placing gold on a π+-surface: ligand design and impact on reactivity

We describe a novel gold chloride complex supported by an ambiphilic phosphine/xanthylium ligand in which the AuCl moiety interacts with the pi(+) surface of the xanthylium unit as indicated by structural studies. Energy decomposition analyses carried out on a model system indicates the prevalence of non-covalent interactions in which the electrostatic and dispersion terms cumulatively dominate. The presence of these AuCl-pi(+) interactions correlates with the high catalytic activity of this complex in the cyclisation of 2-(phenylethynyl)phenylboronic acid, N-propargyl-t-butylamide, and 2-allyl-2-(2-propynyl)malonate. Comparison with the significantly less active acridinium and the 9-oxa-10-boraanthracene analogues reinforces this conclusion.

Automated summary

We have described a new gold chloride complex with an ambiphilic phosphine/xanthylium ligand, in which the AuCl interacts with the pi(+) surface of the xanthylium unit. Energy decomposition analyses on a model system revealed the dominance of non-covalent interactions, particularly electrostatic and dispersion terms. The presence of these AuCl-pi(+) interactions correlates with the high catalytic activity of the complex in various cyclisation reactions.