Priyadharshini Velmurugan, Shashi Kumar, Bhaskar Baruah, Arnab Rit
Unsymmetrical bis-N-heterocyclic carbene (NHC) ligand (bearing 1,2,3-triazolylidene (1,2,3-tzNHC) and benzimidazolylidene (bzNHC) donors)-supported homobimetallic Pd(II) complexes, with (2) or without (1) a phenylene spacer, were synthesized and evaluated in demanding Suzuki-Miyaura couplings of chloroarenes. The spacer-free complex 1 exhibited superior activity to that of 2, despite showing Pd-Pd cooperativity, attributed to conformational rather than electronic effects, as supported by experimental and computational studies. In contrast, electronic effects dictate the activity trends among the spacer-free complexes 1, 3, and 4, which differ in the identity of one of the NHC donors (1,2,3-triazolylidene, imidazolylidene, and 1,2,4-triazolylidene, respectively).