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Title: Synthesis, dynamics and redox properties of eight-coordinate zirconium catecholate complexes
Reaction of the 9,9-dimethylxanthene-bis(imine)-bis(catechol) ligand XbicH 4 with half an equivalent of Zr(acac) 4 affords the neutral tetracatecholate complex (XbicH 2 ) 2 Zr, containing four iminium ions hydrogen bonded to the catecholates. The heteroleptic bis(catecholate)-tetraphenylporphyrin complex (TPP)Zr(XbicH 2 ) is formed from reaction of (TPP)Zr(OAc) 2 with XbicH 4 in the presence of base. Both compounds adopt an eight-coordinate square antiprismatic geometry around the zirconium center. NMR spectra of (TPP)Zr(XbicH 2 ) show that it is fluxional at room temperature, with homoleptic (XbicH 2 ) 2 Zr showing fluxionality at higher temperatures. Calculations and kinetic isotope effect measurements suggest that the motions involve dissociation of a single catecholate oxygen and subsequent twisting of the seven-coordinate species. The compounds show reversible one-electron oxidations of each of the bound catecholates to bound semiquinones.  more » « less
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Journal Name:
Dalton Transactions
Page Range / eLocation ID:
11648 to 11656
Medium: X
Sponsoring Org:
National Science Foundation
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