A synthetic route is reported towards ruthenium-based structural mimics of the [Fe]-hydrogenase metal cofactor in which the acyl moiety is replaced by an N-heterocyclic carbene. It is observed that the pyridyl-NHC ligand has a rather different trans influence from that of a simple NHC in their ruthenium derivatives. The basis for this difference is explored crystallographically and computationally, and it accounts for their different behaviour towards thiolation. © 2020 Wiley-VCH GmbH