Bis[cyclic (alkyl)(amino)carbene] isomers: Stable -bis(CAAC) facile olefin formation for -bis(CAAC).

Isomeric bis(aldiminium) salts with a 1,4-cyclohexylene framework were synthesized. The first isolable bis(CAAC) was prepared from the -stereoisomer and its ditopic ligand competency was proven by conversion to iridium(I) and rhodium(I) complexes. Upon deprotonation, the -isomer yielded an electron rich olefin a classic, proton-catalyzed pathway. The CC bond formation from the desired -bis(CAAC) was shown to be thermodynamically very favorable and to involve a small activation barrier. Compounds that can be described as insertion products of the -bis(CAAC) into the E-H bonds of NH, CHCN and HO were also identified.