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Di‐ and Trinuclear Zinc and Cobalt Complexes and Their Reactivity towards Dioxygen
Author(s) -
Siewert Inke,
Sietzen Malte,
Dechert Sebastian,
Demeshko Serhiy
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201300287
Subject(s) - chemistry , cobalt , reactivity (psychology) , zinc , ligand (biochemistry) , medicinal chemistry , pyridine , metal , inorganic chemistry , stereochemistry , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology
A new ligand L – with two adjacent pyrazole–pyridine moieties, which are linked by a CHO – unit was developed and utilised to synthesise three multinuclear metal complexes. The reaction of HL with NEt 3 and zinc(II) halides or cobalt(II) chloride leads to complexes of the type [M 2 L 2 ] 2+ (M = Co, Zn). Temperature‐dependent magnetic measurement of [Co 2 L 2 ](PF 6 ) 2 ( I ) showed a ferromagnetic coupling of the Co ions. Subsequently, the reactivity of these complexes with O 2 was investigated. Complex I reacts with O 2 to form a cobalt(II) complex in which the ligand is oxygenated at the central carbon atom, that is, a gem ‐diol is formed. As [Zn 2 L 2 ](PF 6 ) 2 ( II ) does not react with O 2 , the Co ions mediate the oxygenation of the ligand in [Co 2 L 2 ] 2+ . The reaction of Zn(OAc) 2 with HL under inert conditions leads to the formation of the trinuclear complex [Zn 3 L(OAc) 5 ] ( III ), which decomposes in air. Further investigation showed that O 2 causes ligand oxidation in the central carbon position, which leads to the corresponding ketone upon decomplexation. The primary decomposition products are presumably gem ‐diolate zinc species. These results point to different reaction mechanisms for the activation of dioxygen by I and III .