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Titolo:
Hydrogen-bonding cavities about metal ions: Synthesis, structure, and physical properties for a series of monomeric M-OH complexes derived from water
Autore:
MacBeth, CE; Hammes, BS; Young, VG; Borovik, AS;
Indirizzi:
Univ Kansas, Dept Chem, Lawrence, KS 66045 USA Univ Kansas Lawrence KS USA 66045 nsas, Dept Chem, Lawrence, KS 66045 USA Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA Univ Minnesota Minneapolis MN USA 55455 t Chem, Minneapolis, MN 55455 USA
Titolo Testata:
INORGANIC CHEMISTRY
fascicolo: 18, volume: 40, anno: 2001,
pagine: 4733 - 4741
SICI:
0020-1669(20010827)40:18<4733:HCAMIS>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
ZINC HYDROXIDE COMPLEX; CARBONIC-ANHYDRASE; NITRILE HYDRATASE; CRYSTAL-STRUCTURE; SMALL-MOLECULE; LIGAND; MODEL; IRON; CHEMISTRY; MECHANISM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
53
Recensione:
Indirizzi per estratti:
Indirizzo: Borovik, AS Univ Kansas, Dept Chem, Lawrence, KS 66045 USA Univ Kansas Lawrence KS USA 66045 hem, Lawrence, KS 66045 USA
Citazione:
C.E. MacBeth et al., "Hydrogen-bonding cavities about metal ions: Synthesis, structure, and physical properties for a series of monomeric M-OH complexes derived from water", INORG CHEM, 40(18), 2001, pp. 4733-4741

Abstract

The tripodal ligand N[CH2CH2NHC(O)NHC(CH3)(3)](3) ([H(6)1]) was used to synthesize a series of monomeric complexes with terminal hydroxo ligands. Thecomplexes [Co(II/III)H(3)1(OH)](2-/1-), [Fe(II/III)H(3)1(OH)](2-/1-), and [Zn(II)H(3)1(OH)](2-) have been isolated and characterized. The source of the hydroxo ligand in these complexes is water, which was confirmed with an isotopic labeling study for [Co(III)H(3)1(OH)](1-). The synthesis of [M(II)H(3)1(OH)](2-) complexes was accomplished by two routes. Method A used 3 equiv of base prior to metalation and water binding, affording yields of lessthan or equal to 40% for [Co(II)H(3)1(OH)](2-). When 4 equiv of base was used (method B), yields ranged from 50% to 70% for all of the M(II)H(3)1(OH)](2-) complexes. This improvement is attributed to the presence of an intramolecular basic site within the cavity, which. scavenges protons produced during formation of the M-II-OH complexes. The molecular structures of [Zn(II)H(3)1(OH)](2-), [Fe(II)H(3)1(OH)](2-), [Co(II)H(3)1(OH)](2-), and [Co(III)H(3)1(OH)](1-) were examined by X-ray diffraction methods. The complexes have trigonal bipyramidal coordination geometry with the hydroxo oxygen trans to the apical nitrogen. The three M-II-OH complexes crystallized with nearly identical lattice parameters, and each contains two independent anions in the asymmetric unit. The complexes have intramolecular H-bonds from the urea cavity of [H(3)1](3-) to the coordinated hydroxo oxygen. All the complexes have long M-O(H) bond lengths (> 2.00 Angstrom) compared to those of the few previously characterized synthetic examples. The longer bond distances in [M(II)H(3)1(OH)](2-) reflect the intramolecular H-bonds in the complexes. The five-coordinate [Zn(II)H(3)1(OH)](2-) has an average Zn-O(H) distance of 2.024(2) Angstrom, which is similar to that found for the zinc site in carbonic anhydrase H (2.05(2) Angstrom). The enzyme active site also hasan extensive network of intramolecular H-bonds to the hydroxo oxygen. [Co(II)H(3)1(OH)]2- and [Fe(II)H(3)1(OH)]2- have one-electron redox processes at -0.74 and -1.40 V vs SCE. Both complexes can be chemically oxidized to yield their corresponding M-III-OH complexes. [Co(III)H(3)1(OH)](1-), with anS = 1 ground state, is a rare example of a paramagnetic Co-III complex.

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Documento generato il 28/09/20 alle ore 18:44:32