As it is clear that the initial step in catalyst decomposition is the rotation of the N-aryl until it is coplanar with the imidazolidinylidene ring, some effort has been put into the synthesis of NHCbased Ru complexes with restricted N-aryl rotation while maintaining the low steric demand of the NHC ligand. Our group has recently published an example showing how such an approach can deliver enhanced catalyst stability and productivity (Figure ). Perhaps due to their limited applications, benzimidazolylidene ruthenium catalysts did not gain much interest. Delaude and co-workers reported, in their scholarly work, the synthesis of ruthenium catalysts having benzimidazolylidene NHC ligand with ortho-tolyl (Ru7, Figure ) and mesityl N-substituents. We reasoned that such a ligand architecture would be ideal for the installation of a second decker of aromatic rings, which would hinder the N-aryl rings' rotation. According to this working hypothesis, catalysts Ru16 and Ru17 (Figure ), featuring the smallest possible set of aryl N-substituents at the NHC ligand, i.e. phenyl groups, may display higher stability than their parent complex Ru5, while their activity in the challenging metathesis of sterically crowded bonds would be maintained and, hopefully, even enhanced. Electronically-different phenyl (in Ru16) and pentafluorophenyl (in Ru17) groups were chosen as second-decker aryl groups to investigate the possible peculiarities of these hitherto unknown architectures, such as a potential presence of π-π interactions and modulated electronic properties.