Mono-, di- and tetra-nuclear p-cymeneruthenium complexes containing oxalato ligands

Abstract

The oxalato complexes [Ru₂(µ-η⁴-C₂O₄)Cl₂(η⁶-p-PrⁱC₆H₄Me)₂] 1 and [Ru(η²-C₂O₄)(NH₃)(η⁶-p-PrⁱC₆H₄Me)] 2 have been prepared from the reaction of ammonium oxalate with [{RuCl₂(η⁶-p-PrⁱC₆H₄Me)}₂] and [Ru(H₂O)₃(η⁶-p-PrⁱC₆H₄Me)]²⁺, respectively. With triphenylphosphine, 1 reacted to give [Ru₂(µ-η⁴-C₂O₄)(PPh₃)₂(η⁶-p-PrⁱC₆H₄Me)₂]²⁺ 3, while 2 gave [Ru(η²-C₂O₄)(PPh₃)(η⁶-p-PrⁱC₆H₄Me)] 4. The dichloro complex 1 can also be converted into the cationic dimethanol complex [Ru₂(µ-η⁴-C₂O₄)(MeOH)₂(η⁶-p-PrⁱC₆H₄Me)₂]²⁺ 5 by precipitation of the chloride with a silver salt in methanol. Complex 5 reacted with 4,4′-bipyridine to afford a novel tetranuclear metallomacrocycle [Ru₄(µ-η⁴-C₂O₄)₂(µ-η¹∶η¹-bipy)₂(η⁶-p-PrⁱC₆H₄Me)₄]⁴⁺ 6 with alternating oxalato and 4,4′-bipyridine bridges. The reaction between 1 and azide yielded the known azido-bridged complex [{Ru(µ-η¹-N₃)Cl(η⁶-p-PrⁱC₆H₄Me)}₂] 7. The molecular structures of 1 (two conformational isomers), 4, 5 and 6 have been solved by X-ray crystallography.