COMPARATIVE BONDING PROPERTIES OF SEMIQUINONATE AND IMINOSEMIQUINONATE RADICAL LIGANDS IN RN(CO)(2)(3,6-DBSQ)(2) AND RU(CO)(2)(PHENOXSQ)(2)

Semiquinonate and iminosemiquiononate complexes of ruthenium have been prepared by treating Ru-3(CO)(12) with 3,6-di-tert-butyl-1,2-benzoqui none (3,6-DBBQ) and 2,4,6, 8-tetra-tert-butylphenoxazin-1-one (PhenoxB Q). Crystallorgraphic characterization of Ru(CO)(2)(3,6-DBSQ)(2) obtai ned as the 2-propanol solvate (tetragonal, P (4) over bar 2(1)c, a = 1 9.066(2) Angstrom, c = 18.420(5) Angstrom, V = 6696(2) Angstrom(3), Z = 8, R = 0.041) has shown that the carbonyl ligands are coordinated at cis sites. Structural characterization of Ru(CO)(2)(PhenoxSQ)(2) carr ied out on crystals obtained as the dichloromethane solvate (orthorhom bic, Pbca, a = 31.215(6) Angstrom, b = 12.393(3)Angstrom, c = 30.664(6 )Angstrom, V = 11862(5)Angstrom(3), Z = 8, R = 0.069) has shown that t he carbonyl ligands bond at cis sites that are trans to the iminosemiq uinone oxygen atoms. Radical ligands are antiferromagnetically coupled , resulting in diamagnetism and sharp NMR spectra for both complex mol ecules. Five-membered redox series consisting of two oxidations and tw o reductions, all ligand-based, appear in the electrochemistry. Potent ials of iminoquinone couples are shifted negatively by approximately 0 .5 V relative to corresponding quinone redox steps.