The complexes Ru(CO) 2 L 2 (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 ) PPh 3 , PCy 3 , PBu 3 ), and Ru(CO)(dppe)(PBu 3 )(PHAQ-2H), containing catecholate-type ligands were prepared. The complex Ru(CO) 2 -(PBu 3 ) 2 (AG-2H) crystallizes in the space group P2 1 /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) 2 L 2 (PHAQ-2H)] 1+ and [Ru(CO)(dppe)(PBu 3 )(PHAQ-2H)] 1+ were generated by chemical oxidation. One example of an o-acylphenolate complex, HRu(CO)(PCy 3 ) 2 (PUR-H), is also reported. * To whom correspondence should be addressed.(1) Throughout this paper the following abbreviations are used: purpurin (1,2,4-trihydroxy-9, 10-anthracenedione), PUR; anthragallol (1,2,3trihydroxy-9, 10-anthracenedione), AG; quinalizarin (1,2,5,8-tetrahydroxy-9, 10-anthracenedione), QAL. The removal of one hydroxyl proton is indicated by "-H" and of two hydroxyl protons as "-2H"; removal of three hydroxyl protons and O-methylation is indicated by "-3H+Me". (2) For example, see: (a)