New Structural Motifs Resulting from Internal Constraints in Chelating Bis(NHC) Ligands: A Dinuclear Ruthenium(II) Complex Featuring an η<sup>2</sup>‑Arene Binding Mode and a Remarkable New Tetrameric Silver(I) Halide Form Peter V. Simpson David H. Brown Brian W. Skelton Allan H. White Murray V. Baker 10.1021/om5012165.s001 https://acs.figshare.com/articles/journal_contribution/New_Structural_Motifs_Resulting_from_Internal_Constraints_in_Chelating_Bis_NHC_Ligands_A_Dinuclear_Ruthenium_II_Complex_Featuring_an_sup_2_sup_Arene_Binding_Mode_and_a_Remarkable_New_Tetrameric_Silver_I_Halide_Form/2160538 A novel dinuclear ruthenium­(II) complex containing two <i>ortho</i>-xylylene-linked bis­(NHC) ligands (NHC = N-heterocyclic carbene) has been synthesized via transmetalation from a silver-NHC complex. Each ruthenium atom in the dinuclear complex is chelated through the two carbene carbon atoms and, unusually, an η<sup>2</sup>-bound xylylene ring, two separate bis­(NHC) units being linked by a Ru­(μ-Cl)<sub>3</sub>Ru core. The same bis­(NHC) ligand has yielded a neutral tetranuclear 4:2 AgBr:bis­(NHC) complex, where ligand steric constraints seemingly inhibit formation of structures derivative of the more familiar “cubane” or “step” forms, resulting in an interesting new structural type. 2015-06-08 00:00:00 New Structural Motifs Resulting dinuclear NHC Internal Constraints ruthenium atom bi ligand steric constraints carbene carbon atoms xylylene ring