Two-Step Assembly of Multinuclear Metallacycles with Half-Sandwich Ir, Rh, and Ru Fragments for Counteranion Encapsulation

Abstract

Two-step reactions of [Cp*M(mu-Cl)Cl](2) (M = Ir, Rh) and [(p-cymene)Ru(mu-Cl)Cl](2) with first AgOTf or AgPF(6) and then pyridyl-substituted dionate ligands [3-(4-pyridyl)pentane-2,4-dione (L(1)), 1-(4-pyridinyl)butane-1,3-dione (L(2)), 1-(3-pyridinyl)butane-1,3-dione (L(3))] resulted in the formation of the hexanuclear 48-membered metallacycles [(Cp*Ir)(L(1))](6) x (OTf)(6) (1) and [(Cp*Rh)(L(1))](6) x (OTf)(6) (2), the tetranuclear 28-membered metallacycle [(Cp*Ir)(L(2))](4) x (OTf)(4) (3), and the 24-membered metallacycle [(p-cymene)Ru(L(3))](4) x (OTf)(4) (4), as well as the hexanuclear 48-membered metallacycles {[(p-cymene)Ru(L(1))](6)(OTf)} x (OTf)(5) (5) and {[(p-cymene)Ru(L(1))](6)(PF(6))} x (PF(6))(5) (6) showing encapsulation of the counteranions. Compounds 1-6 were characterized by single crystal X-ray analyses and revealed that these metallacycles constructed from half-sandwich metal corners and pyridyl-substituted diketone linkers formed large ring structures. In addition, when the couteranions of 5 and 6 were exchanged, the shapes and sizes of the host units [(p-cymene)Ru(L(1))](6)(6+) underwent some self-adjustment to allow for accommodation of the different anionic guests. Weak hydrogen bonding of the type C(S)-F(O)...H-C(sp(3)) and P-F...H-C(sp(3)) and electrostatic interactions are considered the basic forces to establish the metallacyclic units in 5 and 6 with anion encapsulation. The found variation in the metallacyclic geometries was explained on the basis of a structural flexibility of the corner fragments, subtle changes in coordination geometries, and changes in the orientation of the coordinate vectors in the given ligands, as well as the dihedral angles between the two binding fragments (the chelate and the monodentate fragments) in the nonplanar ligands.