“…As in the analogous nickel(II) complexes, the above reactions are facile and occur very rapidly at room temperature and in other solvents such as methanol. Reaction of 1 with glutarodihydroxamic acid, (CH 2 ) 3 (CONHOH) 2 , gluH 2 A 2 , at room temperature in methanol in the presence of triflate gave [Co 2 (μ-OAc) 2 {μ-O(N)(OC) 2 (CH 2 ) 3 }(tmen) 2 ][OTf] ( 5 ) which contains a deprotonated bridging N -hydroxyglutarimide (Figure ) as in the analogous dinickel complex 1 Molecular structure of the cation of dicobalt(II) complex 2, [Co 2 (μ-OAc) 3 (urea)(tmen) 2 ] + . 2 Molecular structure for the cation of dicobalt(II) monobridged acetohydroxamate complex 3 , [Co 2 (μ-OAc) 2 (μ-AA)(urea)(tmen) 2 ] + . 3 Molecular structure for the cation of dicobalt(II) dibridged acetohydroxamate complex 4 , [Co 2 (μ-OAc)(μ-AA) 2 (tmen) 2 ] + . 4 Molecular structure for the cation of dicobalt(II) complex 5 , [Co 2 (μ-OAc) 2 {μ-O(N)(OC) 2 (CH 2 ) 3 }(tmen) 2 ] + . …”
Section: Resultsmentioning
confidence: 99%
“…Moreover, addition of 1 mol of these ions to apo-AAP followed by equilibration and then addition of 1 mol of the second metal ion gives a discrete heterodimetallic site that is also enzymatically active . In previous papers, , we have attempted to model the inhibition of urease by hydroxamic acids by the reactions of acetohydroxamic acid (AHA) with the model complex [Ni 2 (μ-OAc) 3 (urea)(tmen) 2 ][OTf] ( A ), which reacts rapidly with acetohydroxamic acid (AHA) to give the monobridged hydroxamate complex [Ni 2 (μ-OAc) 2 (μ-AA)(urea)(tmen) 2 ][OTf] with a structure very similar to that of the acetohydroxamate inhibited C319A variant of Klebsiella aerogenes urease …”
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.
“…As in the analogous nickel(II) complexes, the above reactions are facile and occur very rapidly at room temperature and in other solvents such as methanol. Reaction of 1 with glutarodihydroxamic acid, (CH 2 ) 3 (CONHOH) 2 , gluH 2 A 2 , at room temperature in methanol in the presence of triflate gave [Co 2 (μ-OAc) 2 {μ-O(N)(OC) 2 (CH 2 ) 3 }(tmen) 2 ][OTf] ( 5 ) which contains a deprotonated bridging N -hydroxyglutarimide (Figure ) as in the analogous dinickel complex 1 Molecular structure of the cation of dicobalt(II) complex 2, [Co 2 (μ-OAc) 3 (urea)(tmen) 2 ] + . 2 Molecular structure for the cation of dicobalt(II) monobridged acetohydroxamate complex 3 , [Co 2 (μ-OAc) 2 (μ-AA)(urea)(tmen) 2 ] + . 3 Molecular structure for the cation of dicobalt(II) dibridged acetohydroxamate complex 4 , [Co 2 (μ-OAc)(μ-AA) 2 (tmen) 2 ] + . 4 Molecular structure for the cation of dicobalt(II) complex 5 , [Co 2 (μ-OAc) 2 {μ-O(N)(OC) 2 (CH 2 ) 3 }(tmen) 2 ] + . …”
Section: Resultsmentioning
confidence: 99%
“…Moreover, addition of 1 mol of these ions to apo-AAP followed by equilibration and then addition of 1 mol of the second metal ion gives a discrete heterodimetallic site that is also enzymatically active . In previous papers, , we have attempted to model the inhibition of urease by hydroxamic acids by the reactions of acetohydroxamic acid (AHA) with the model complex [Ni 2 (μ-OAc) 3 (urea)(tmen) 2 ][OTf] ( A ), which reacts rapidly with acetohydroxamic acid (AHA) to give the monobridged hydroxamate complex [Ni 2 (μ-OAc) 2 (μ-AA)(urea)(tmen) 2 ][OTf] with a structure very similar to that of the acetohydroxamate inhibited C319A variant of Klebsiella aerogenes urease …”
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.
“…13 Some other practical areas involving hydroxamic acids and their complexes include removal of toxic elements by solvent extraction, 14 usage as efficient and environmentally friendly corrosion inhibitors, 15 applications as collectors for flotation of minerals, 16 antioxidant acivity, 17 and their potential as redox switches for electronic devices. 18 Amazingly, such a broad spectrum of activity of hydroxamic acids is almost exclusively associated with only one type of chemical reactions; that is, their ability to bind a large variety of metal ions forms, in the vast majority of cases, O,O five-membered chelate rings [19][20][21] (bridging 22,23 and monodentate 24 coordination modes are also known, although scarce), and these complexes are often characterized by very high stability constants. 21 Although hydroxamic acids have been known for over a century, 25 their reactivity modes involving metal centers, besides the complex forming properties, are practically unexplored; among the rare exceptions are the recently described deoxygenation of the N-OH group occurring at Os(III) and Rh(I) centers, 26 Ni(II)-assisted hydroxylamine elimination, 23 and reductive cleavage of the N-O bond with SmI 2 .…”
The reaction between the nitrile complex trans-[PtCl(4)(EtCN)(2)] and benzohydroxamic acids RC(6)H(4)C([double bond]O)NHOH (R = p-MeO, p-Me, H, p-Cl, o-HO) proceeds smoothly in CH(2)Cl(2) at approximately 45 degrees C for 2-3 h (sealed tube) or under focused 300 W microwave irradiation for approximately 15 min at 50 degrees C giving, after workup, good yields of the imino complexes [PtCl(4)[NH[double bond]C(Et)ON[double bond]C(OH)(C(6)H(4)R)](2)] which derived from a novel metalla-Pinner reaction. The complexes [PtCl(4)[NH[double bond]C(Et)ON[double bond]C(OH)(C(6)H(4)R)](2)] were characterized by elemental analyses (C, H, N), FAB mass spectrometry, and IR and (1)H and (13)C[(1)H] spectroscopies, and [PtCl(4)[NH[double bond]C(Et)ON[double bond]C(OH)(Ph)](2)] (as the bis-dimethyl sulfoxide solvate), by X-ray single-crystal diffraction. The latter disclosed its overall trans-configuration with the iminoacyl species in the hydroximic tautomeric form in E-configuration which is held by N[bond]H...N hydrogen bond between the imine [double bond]NH atom and the hydroximic N atom.
“…Compound 104 containing a deprotonated bridging N-hydroxyglutarimide was obtained in an unusual hydroxylamine elimination and cyclization reaction upon reaction of 67 with glutarodihydroxamic acid [196] …”
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