Structural systematics for o-C6H4XY ligands with X,Y= O, NH, and S donor atoms.: o-Iminoquinone and o-iminothioquinone complexes of ruthenium and osmium

The structural features of quinone ligands are diagnostic of charge. The o-benzoquinone, radical semiquinonate, and catecholate electronic forms have C-O bond lengths and a pattern of ring C-C bond lengths that point to a specific mode of coordination. This correlation between ligand charge and structure has been extended to iminoquinone and iminothioquinone ligands, giving a charge-localized view of electronic structure for complexes of redox-active metal ions. The radical semiquinonate form of these ligands has been found to be a surprisingly common mode of coordination; however, the paramagnetic character of the radical ligand is often obscured in complexes containing paramagnetic metal ions. In this report, diamagnetic iminosemiquinonate (isq) and iminothiosemiquinonate (itsq) complexes of Is-d(5) Ru(III) with related complexes of osmium are reported. With osmium, the Os(IV)-amidophenolate (ap) redox isomer is formed. Electrochemical and spectral properties are described for Ru(PPh3)(2)(isq)Cl-2, Ru(PPh3)(2)(itsq)Cl-2, Os(PPh3)(2)(ap)Br-2, Os(PPh3)(2)(atp)Br-2, and Os(PPh3)2(ap)H-2. Crystallographic characterization of Ru(PPh3)(2)(isq)Cl-2, Ru(PPh3)(2)(itsq)Cl-2, and Os(PPh3)(2)(ap)H-2 was used to assign charge distributions.