Dioxygen binding and activation by a highly reactive Cr(II) compound containing S,N-donors derived from o-aminothiophenol

• Published in: Journal of coordination chemistry 2012-10, Vol.65 (19), p.3329-3351
• Main Authors: Koley, Manjuri K., Sivasubramanian, Seshadri C., Biswas, Sumit, Manoharan, Periakaruppan T., Koley, Aditya P.
• Format: Article
• Language: English
• Subjects: Activation; Binding; Cleavage; Deoxyribonucleic acid; Disproportionation; DNA interaction; EPR and electronic spectra; Oxo-chromium(IV) complex; Oxo-chromium(V) complex; Scavengers; Spontaneous; Superoxo-Cr(III) complex; Synthesis
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2012.714867

We report the synthesis, characterization, and reactivity of a Cr(II) complex, [Cr(H 2 O)(L ISQ ) 2 ] (1) [(L ISQ ) 1− is o-iminothionebenzosemiquinonate(1−) π-radical], that is highly stable in solid state in the presence of air but undergoes spontaneous change in solution, both in the presence and absence of air. Physicochemical studies in solution show that a superoxo-Cr III species, [Cr(O 2 )(OH)(L ISQ ) 2 ] − is generated initially in DMF solution of 1 in the presence of air owing to its immediate deprotonation followed by O 2 binding to the deprotonated species. The formation of this superoxo-Cr III species is prominent and gradual in the presence of CH 3 OH, a scavenger of CrO 2+ species. This Cr(O 2 ) 2+ species in turn is converted to another highly reactive O=Cr(IV) intermediate [O=Cr(OH)(L ISQ ) 2 ] − which undergoes disproportionation producing an unstable O=Cr(V) species, [O=Cr(OH)(L ISQ ) 2 ] and a stable Cr(III) compound, [Cr(OH)(DMF)(L ISQ ) 2 ] (2). The rate of this disproportionation is enhanced in the presence of MnCl 2 , [N(n-Bu) 4 ]PF 6 and KSCN. The generated O=Cr(IV) species interacts with DNA with complete cleavage. The O=Cr(V) species slowly disappears from solution as revealed from EPR studies.