Homo- and Heterodinuclear Complexes with Triazolyl-diylidene. An Easy Approach to Tandem Catalysts

The reaction of 1,2,4-trimethyltriazolium tetrafluoroborate ([LH2](BF4)2) with several metal precursors provides a series of homo- and heterodimetallic compounds of Rh and Ir. The reaction of [LH2](BF4)2 with [Cp*IrCl2]2 in the presence of NaH in MeOH yields the monocarbene complex [Cp*Ir(LH)Cl2](BF4), which is a very convenient synthon to the preparation of heterodimetallic species through the deprotonation of the remaining NCHN group. Three crystal structures of dimetallic compounds of di-iridium(III), iridium(III)/iridium(I), and iridium(III)/rhodium(I) are described. The complexes obtained have been tested in a tandem catalytic reaction implying the consecutive oxidative cyclization of 2-aminophenyl ethyl alcohol and the alkylation of the resulting imidazole with a series of primary alcohols. The new catalysts show high activity in the overall reaction process, and the selectivity in the production of the bisindolylmethane or monoalkylated indole is tuned by changing the indole/alcohol molar ratio.