Unexpected structural preference with metallophilic Ag-Au contacts in silver(I)-N-heterocyclic carbene cluster; experimental and theoretical approach.

A novel synthetic donor-atom-selective approach has been adopted for the synthesis of a heterobimetallic cluster of a new NCN-pincer, 1,3-bis-(1-methyl-1 H -benzo[ d ]imidazol-2-yl-methyl)-1 H -imidazol-3-ium hexafluorophosphate (1·HPF 6 ). The complex [Ag 3 (1) 3 ][PF 6 ] 3 (2) has been prepared via the Ag 2 O route; which undergoes transmetallation to yield a cluster that seems to be the first example of the heterobimetallic trinuclear system [Au-Ag 2 (1) 2 Cl][PF 6 ] 2 , 3. Finally, the trinuclear cluster geometries of 2 and 3 were confirmed via SCXRD studies. Interestingly, Au(I) binds preferentially with soft donor C carbene , which transmetallated from the cluster of 2. In both the cyclic trinuclear clusters, the M-M interactions were further inspected using gauge independent atomic orbital (GIAO) computations. Both 2 and 3 are luminescent and possess σ-aromaticity; the NICS values indicate that 3 is more aromatic than 2.