Magnetic, spectroscopic, and structural studies of dicobalt hydroxamates and model hydrolases.
The cobalt(II) urease model complex [Co(2)(mu-OAc)(3)(urea)(tmen)(2)][OTf] (2) prepared from the cobalt model hydrolase [Co(2)(mu-H(2)O)(mu-OAc)(2)(OAc)(2)(tmen)(2)] (1) undergoes facile reaction with acetohydroxamic acid (AHA) to give the monobridged hydroxamate complex [Co(2)(mu-OAc)(2)(mu-AA)(urea)(tmen)(2)][OTf]( )()(3) while 1 gives the dibridged hydroxamate complex [Co(2)(mu-OAc)(mu-AA)(2)(tmen)(2)][OTf] (4). The structures and Co-Co distances of the hydroxamate derivatives of 1 and 2 are very close to those of their nickel analogues and suggest that hydroxamic acids can also inhibit cobalt-based hydrolases as well as inhibiting urease. 1 also reacts with glutarodihydroxamic acid (gluH(2)A(2)) to eliminate hydroxylamine with formation of [Co(2)(mu-OAc)(2)[mu-O(N) (OC)(2)(CH(2))(3)](tmen)(2)][OTf] (5), the structure of which is very close to that of its nickel analogue. Both 1 and 3 show weak antiferromagnetic coupling. Oxidation of 1 with H(2)O(2) gives three dicobalt(III) hydroxy complexes (7-9), the first of which [Co(2)(mu-OAc)(2)(OAc)(2)(mu-OH)(tmen)(2)][OTf] (7) contains a bridging hydroxyl and the second [Co(2)(mu-OAc)(2)(OAc)(mu-OH)(OH)(tmen)(2)][OTf] (8) containing both a bridging and terminal hydroxyl, while the third [Co(2)(mu-OAc) (OAc)(2)(mu-OH)(2)(tmen)(2)][OTf] (9) contains two bridging OH groups with mixed-valence Co(II)/(Co(III) intermediates.
Brown
D A
DA
Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland.
Errington
W
W
Glass
W K
WK
Haase
W
W
Kemp
T J
TJ
Nimir
H
H
Ostrovsky
S M
SM
Werner
R
R
D000465:Algorithms; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006861:Hydrogen Peroxide / Q000737:chemistry; D006867:Hydrolases / Q000737:chemistry*; D006877:Hydroxamic Acids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014510:Urease / Q000737:chemistry
D006877:Hydroxamic Acids; D009942:Organometallic Compounds; D003035:Cobalt; C006358:acetohydroxamic acid; D006861:Hydrogen Peroxide; D006867:Hydrolases; D014510:Urease