Dinuclear complexes of silver(I) and gold(I) with macrocyclic dicarbene ligands bearing a 2,6-lutidinyl bridge: synthesis, structural analysis and dynamic behaviour in solution

Dinuclear silver(I) and gold(I) complexes with nonsymmetric macrocyclic dicarbene ligands featured by a 2,6-lutidinyl bridge as well as by a linker 3–4 carbon atoms long (1,3-propylene, o-xylylene, and 1,4-butylene) between two N-heterocyclic carbene groups have been prepared and structurally characterised. All complexes are formed as a mixture of two isomers, which have been interpreted as syn and anti isomers. Whereas in the case of the gold(I) complexes the two isomeric forms do not interconvert at a measurable rate, fast interconversion is recorded with the silver(I) complexes. Finally, the capability of the gold(I) complexes to act as organometallic ligands towards additional group 11 metal centres has been preliminarily evaluated.