Self-assembly of arene ruthenium acylpyrazolone fragments to tetranuclear metallacycles. Molecular structures and solid-state (15)N CPMAS NMR correlations.

Reactions of [(η(6)-cymene)Ru(μ-Cl)Cl]2 with acylpyrazolone ligands HQ' (HQ' in general; in detail, HQ(CH2Cl) = 2-chloro-1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethanone), HQ(hex) = 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)heptan-1-one), HQ(nPe) = 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-3,3-dimethylbutan-1-one)), in the presence of base, gave the corresponding [(η(6)-cymene)Ru(Q')Cl] mononuclear complexes. They react with AgX (where X = O3SCF3 or BF4) in dry acetone affording cationic metalla-cycles [(η(6)-cymene)Ru(Q')]4(X)4. The complexes were fully characterized by analytical and spectroscopic methods and the solid-state structures of mononuclear and tetranuclear complexes have been determined by single-crystal X-ray diffraction. The hapticity of the acylpyrazolone ligands to the Ru metal centre has also been established by (13)C and (15)N CPMAS NMR spectroscopy for the complexes where the lack of crystallinity prevented the elucidation of the crystal structure by SCXRD data.