The catalysts [Ir(COD)(κ 3 - P , C , P′ -PC NHC P)]BF 4 and [Ir(COD)(κ 2 - P,C -PC NHC O)]BF 4 proved to be active in the solventless dehydrogenation of formic acid. The impact of various cosolvents on the activity was evaluated, showing an outstanding improvement of the catalytic performance of [Ir(COD)(κ 2 - P,C -PC NHC O)]BF 4 ] in “green” organic carbonates: namely, dimethyl carbonate (DMC) and propylene carbonate (PC). The TOF 1h value for [Ir(COD)(κ 2 - P,C -PC NHC O)]BF 4 increases from 61 to 988 h –1 upon changing from solventless conditions to a 1/1 (v/v) DMC/HCOOH mixture. However, in the case of [Ir(COD)(PC NHC P)]BF 4 , only a marginal improvement from 156 to 172 h –1 was observed under analogous conditions. Stoichiometric experiments allowed the identification of various key reaction intermediates, providing valuable information on their reactivity. Experimental data and DFT calculations point to the formation of dinuclear species as the catalyst deactivation pathway, which is prevented in the presence of DMC and PC.

The novel P-N ligand 1-((diphenylphosphaneyl)methyl)-1H-benzo-1,2,3-triazole (1), based on a benzotriazole scaffold, has been prepared. The reaction of 1 with [CoCp*(CH3CN)3][BF4]2 and [CoCp*(I)2]2 (Cp* = pentamethylcyclopentadienyl) affords the chelate complexes [CoCp*(CH3CN)(P-N)][BF4]2...

2 a and 2 b, [Ir(CI)(COD)(NHC)] (COD=1,5‐cyclooctadiene), have been prepared via transmetallation from NHC−Ag complexes. [Rh(CI)(COD)(NHC)] (4) was prepared analogously. [Ir({κ‐C,N‐(NHC‐acetamide−1H)}(COD)] (3 c) has been synthesized via transmetallation from the deprotonated NHC−Ag complex. [IrCp*({κ‐C,N‐(NHC‐acetamide−1H)}] (5) (Cp*=pentamethylcyclopentadienyl), has been obtained analogously. [Ir(CI)(CO)2(NHC)] (6) and [Ir({κ‐C,N‐(NHC‐acetamide−1H)}(CO)2] (7) have been prepared by carbonylation of 2 b and 3 c, respectively. The catalytic activity of these complexes has been evaluated in the dehydrogenation of formic acid, under solventless conditions, in the presence of water as a cosolvent, and in a 5 : 2 HCOOH/Et3N mixture, with the best TOF values being obtained in the case of the latter. Stoichiometric experiments suggest COD hydrogenation as the preactivation step.