Heavy Alkaline\nEarth Cyclic (Alkyl)(Amino)Carbene\nComplexes Supported by Aryl–Silyl Amides

A series of 8 trigonal planar, heavy alkaline earth (AE\n= Ca–Ba)\nmetal complexes containing cyclic (alkyl)(amino)carbene (CAAC) ligands\nwere prepared from AE bis(amide) species. Complexation can be achieved\nby first generating the free carbene <i>in situ</i> or by\ndirect addition of the free carbene, with the former route giving\nrise to unexpected mixed-amide AE complexes. The frontier molecular\norbitals of the highly equatorial, 3-coordinate AE-CAAC species were\nalso probed computationally, revealing the lowest unoccupied molecular\norbital (LUMO) consisting predominantly of the π* system located\non the carbene ligand.