Bis[cyclic (alkyl)(amino)carbene] isomers: Stable trans -bis(CAAC) versus facile olefin formation for cis -bis(CAAC).
Braulio M Puerta LombardiEthan R PezoulasRoope A SuvinenAlexander HarrisonZachary S DubrawskiBenjamin S GelfandHeikki M TuononenRoland RoeslerPublished in: Chemical communications (Cambridge, England) (2022)
Isomeric bis(aldiminium) salts with a 1,4-cyclohexylene framework were synthesized. The first isolable bis(CAAC) was prepared from the trans -stereoisomer and its ditopic ligand competency was proven by conversion to iridium(I) and rhodium(I) complexes. Upon deprotonation, the cis -isomer yielded an electron rich olefin via a classic, proton-catalyzed pathway. The CC bond formation from the desired cis -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 cis -bis(CAAC) into the E-H bonds of NH 3 , CH 3 CN and H 2 O were also identified.