Linkage and redox isomerism in ruthenium complexes of catecholate, semi-quinone, and o-acylphenolate ligands derived from tri- and tetrahydroxy-9,10-anthracenediones

The complexes Ru(CO)₂L₂(PHAQ-2H) (PHAQ = 1,2,4-trihydroxy-9,10-anthracenedione (PUR), 1,2,3-trihydroxy-9,10-anthracenedione (AG), and 1,2,5,8-tetrahydroxy-9,10-anthracenedione (QAL); L = PPh₃, PCy₃, PBu₃), and Ru(CO)(dppe)(PBu₃)(PHAQ-2H), containing catecholate-type ligands were prepared. The complex Ru(CO)₂(PBu₃)₂(AG-2H) crystallizes in the space group P2₁/n (No. 14 var) with a = 13.317(2), b = 15.628(2), c = 21.076(3) Å, β = 101.660(10)°, Z = 4; the crystal structure shows it to contain a 2,3-catecholate ligand. The electrochemistry of these complexes was examined, and the semi-quinone complexes [Ru(CO)₂L₂(PHAQ-2H)]¹⁺ and [Ru(CO)(dppe)(PBu₃)(PHAQ-2H)]¹⁺ were generated by chemical oxidation. One example of an o-acylphenolate complex, HRu(CO)(PCy₃)₂(PUR-H), is also reported.