A Tris(carbene) Constructed with Stable Triplet Carbene Units

Abstract

Abstract Bis[10-(4-t-butyl-2,6-dimethylphenyl)-9-anthryl]diazomethane, which can generate a fairly stable triplet carbene that can survive for even a week in solution at room temperature, was shown to be stable enough to undergo a Sonogashira coupling reaction. Thus, three units of the diazo compounds were connected through an ethynyl group on 1,3,5-positions of benzene. The species generated by irradiation of the resulting tris(diazo) compound were characterized by variable temperature ESR and SQUID measurements. The results indicated the generation of the corresponding tris(carbene), that exhibits only weak exchange between carbene units. This fits the fact that dianthrylcarbenes are connected to the central phenyl ring across nodal (inactive) sites. The anomalously high thermal stability and chemical inertness of the species were shown by variable temperature and time-resolved UV–vis spectroscopic studies. The tris(carbenes) are shown to survive hours in solution at room temperature.