Stepwise Formation of Molecular Rectangles of Half-Sandwich Rhodium and Ruthenium Complexes Containing Bridging Chloranilate Ligands

Binuclear complexes [Cp* 2 Rh 2 (μ-CA)Cl 2 ] ( 2a ) and [( p -cymene) 2 Ru 2 (μ-CA)Cl 2 ] ( 2b ) (CA = chloranilate) were obtained by the reactions of [Cp*RhCl(μ-Cl)] 2 ( 1a ) or [( p -cymene)RuCl(μ-Cl)] 2 ( 1b ) with H 2 CA in the presence of base, respectively. Treatment of 2a or 2b with bidentate ligands (L) such as pyrazine, 4,4′-dipyridine (bpy), 2,5-bis(4-pyridyl)-1,3,5-oxadiazole (bpo), and E -1,2-bis(4-pyridyl)ethene (bpe) in the presence of AgOTf (OTf = CF 3 SO 3 ) in CH 3 OH gave the corresponding tetranuclear complexes, with the general formulas [Cp* 4 Rh 4 (μ-CA) 2 (μ-L) 2 ](OTf) 4 ( 3a − d ) and [( p -cymene) 4 Ru 4 (μ-CA) 2 (μ-L) 2 ](OTf) 4 ( 4a − d ), respectively. The molecular structures of [Cp* 4 Rh 4 (μ-CA) 2 (μ-bpy) 2 ](OTf) 4 ( 3b ), [( p -cymene) 4 Ru 4 (μ-CA) 2 (μ-bpy) 2 ](OTf) 4 ( 4b ), and [( p -cymene) 4 Ru 4 (μ-CA) 2 (μ-bpe) 2 ](OTf) 4 ( 4d ) have been determined by single-crystal X-ray analysis and revealed that the metal centers were connected by pyridyl ligands and bis-bidentate chloranilate (CA) ligands to construct a rectangular cavity with different dimensions and strong π interactions between independent molecules to form rectangle channels in the solid state.