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ABSTRACT: Systems formed using the V(IV)O(2+) ion with tridentate ligands containing a (O, Narom, O) donor set were described. Examined ligands were 3,5-bis(2-hydroxyphenyl)-1-phenyl-1H-1,2,4-triazole (H2hyph(Ph)), 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzoic acid (H3hyph(C)), 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzenesulfonic acid (H3hyph(S)), and 2,6-bis(2-hydroxyphenyl)pyridine (H2bhpp), with H3hyph(C) being an orally active iron chelator that is commercially available under the name Exjade (Novartis) for treatment of chronic iron overload arising from blood transfusions. The systems were studied using EPR, UV-Vis, and IR spectroscopies, pH potentiometry, and DFT methods. The ligands bind vanadium with the two terminal deprotonated phenol groups and the central aromatic nitrogen to give six-membered chelate rings. In aqueous solution the main species were the mono- and bis-chelated V(IV)O complexes, whereas in the solid state neutral non-oxido V(IV) compounds were formed. [V(hyph(Ph))2] and [V(bhpp)2] are hexacoordinated, with a geometry close to the octahedral and a meridional arrangement of the ligands. DFT calculations allow distinguishing V(IV)O and V(IV) species and predicting their structure, the (51)V hyperfine coupling constant tensor A, and the electronic absorption spectra. Finally, EPR spectra of several non-oxido V(IV) species were compared using relevant geometrical parameters to demonstrate that in the case of tridentate ligands the (51)V hyperfine coupling constant is related to the geometric isomerism (meridional or facial) rather than the twist angle Φ, which measures the distortion of the hexacoordinated structure toward a trigonal prism.
Inorganic Chemistry 04/2013; · 4.60 Impact Factor
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ABSTRACT: In the structure of the title compound, {[Na(C6H15N3O3)]Br} n , the sodium cation and the bromide anion are both located on threefold rotation axes. The sodium cation is bonded to the three hy-droxy groups of one 1,3,5-triamino-1,3,5-tride-oxy-cis-inositol (taci) ligand, with the taci ligand residing around the same threefold rotation axis as the sodium ion. The coordination sphere of the sodium ion is completed by three amino groups of three neighbouring taci mol-ecules. Hence, this type of coordination constitutes a three-dimensional open framework with channels along the c axis which are filled with the bromide counter-anions. Each bromide ion forms three symmetry-related hydrogen bonds to both the hy-droxy and the amino groups of neighbouring taci ligands.
Acta Crystallographica Section E Structure Reports Online 04/2013; 69(Pt 4):m185-6. · 0.35 Impact Factor
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ABSTRACT: In the title compound, C(20)H(24)N(2)O(5), the dihedral angle between the two roughly planar salicyl-amide fragments [r.m.s. deviations = 0.043 (2) and 0.149 (2) Å] is 25.50 (5)°. The mol-ecular conformation is stabilized by intra-molecular O-H⋯O hydrogen bonds involving phenol -OH groups and amide O atoms. Inter-molecular hy-droxy-meth-yl-amide O-H⋯O and amine-hy-droxy-methyl N-H⋯O hydrogen bonds form infinite chains along the b axis. These chains are further inter-linked by amine-amide N-H⋯O and phenol-phenol O-H⋯O inter-actions, thus giving layers parallel to (001).
Acta Crystallographica Section E Structure Reports Online 02/2013; 69(Pt 2):o223. · 0.35 Impact Factor
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ABSTRACT: The crystal structure of the title compound, CHNO, features centrosymmetric dimers with two amide groups inter-connected by a pair of almost linear N-H⋯O hydrogen bonds. Through inter-molecular O-H⋯O inter-actions between phenolic hy-droxy groups and carbonyl O atoms, these dimers are assembled into undulating hydrogen-bonded layers parallel to the [101] plane. Additionally, the -H(-N) atom of the primary amide group forms an intra-molecular hydrogen bond to the O atom of the meth-oxy group. The amide group froms a dihedral angle of 12.6 (1)° with the phenyl ring.
Acta Crystallographica Section E Structure Reports Online 12/2012; 68(Pt 12):o3494. · 0.35 Impact Factor
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ABSTRACT: The 2-hy-droxy-cyclo-hexane-1,3,5-triaminium (= H(3)L(3+)) cation of the title compound, 3C(6)H(18)N(3)O(3+)·8Cl(-)·HSO(4) (-)·2H(2)O, exhibits a cyclo-hexane chair with three equatorial ammonium groups and one axial hy-droxy group in an all-cis configuration. The hydrogen sulfate anion and two water mol-ecules lie on or in proximity to a threefold axis and are disordered. The crystal structure features N-H⋯Cl and O-H⋯Cl hydrogen bonds. Three C(3)-symmetric motifs can be identified in the structure: (i) Two chloride ions (on the C(3)-axis) together with three H(3)L(3+) cations constitute an [(H(3)L)(3)Cl(2)](7+) cage. (ii) The lipophilic C(6)H(6)-sides of three H(3)L(3+) cations, which are oriented directly towards the C(3)-axis, generate a lipophilic void. The void is filled with the disordered water mol-ecules and with the disordered part of the hydrogen sulfate ion. The hydrogen atoms of these disordered moieties were not located. (iii) Three H(3)L(3+) cations together with one HSO(4) (-) and three Cl(-) counter-ions form an [(HSO(4))(H(3)L)(3)Cl(3)](5+) cage. Looking along the C(3)-axis, these three motifs are arranged in the order (cage 1)⋯(lipophilic void)⋯(cage 2). The crystal studied was found to be a racemic twin.
Acta Crystallographica Section E Structure Reports Online 06/2012; 68(Pt 6):o1899-900. · 0.35 Impact Factor
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ABSTRACT: The crystal structure of the title compound, C(6)H(16)N(2)O(3) (2+)·2Cl(-), has been reported previously by Palm [Acta Cryst. (1967 ▶), 22, 209-216] from Weisenberg camera data, with R1 = 10.5%, isotropic refinement of non-H atoms and H atoms not located. We remeasured a data set of the title compound and present a more precise structure determination. The asymmetric unit contains two unique 1,3-diammonio-1,2,3-tride-oxy-cis-inositol cations and four Cl(-) counter-ions. The cyclo-hexane rings of both inositol cations adopt chair conformations with two axial hy-droxy groups. An extended network of hydrogen bonds is formed. The four chloride counter ions are hydrogen bonded to the hydroxy and ammonium groups of the cations by N-H⋯Cl and O-H⋯Cl interactions. The cations are aligned into wavy layers by cation⋯cation interactions of the form N-H⋯O(ax), N-H⋯O(eq) and O(ax)-H⋯O(eq). Intramolecular hydrogen bonding between the axial hydroxy groups is, however, not observed.
Acta Crystallographica Section E Structure Reports Online 05/2012; 68(Pt 5):o1411-2. · 0.35 Impact Factor
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ABSTRACT: In the crystal structure of the title compound, C(6)H(16)N(2)O(3) (2+)·SO(4) (2-), each cation forms three O-H⋯O and five N-H⋯O hydrogen bonds to six neighbouring sulfate anions. In addition, interlinking of the cations by N-H⋯O interactions is also observed. The cyclo-hexane ring adopts a chair conformation with two axial hy-droxy groups. Although the separation of 2.928 Å is almost ideal for a hydrogen bond, intra-molecular hydrogen bonding between these two hy-droxy groups is not observed.
Acta Crystallographica Section E Structure Reports Online 05/2012; 68(Pt 5):o1425-6. · 0.35 Impact Factor
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ABSTRACT: 3,5-Bis(2-hydroxyphenyl)-1H-1,2,4-triazole (H2La) and 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzoic acid (H3Lb) have been prepared, and crystal structure of the intermediate 2-(2-hydroxyphenyl)-4H-1,3-benzoxazin-4-one has been determined. Temperature dependent 1H NMR spectroscopic measurements of H2La indicated dynamic behavior with the equilibrium between the two asymmetric tautomers. For H3Lb, pD-dependent 1H NMR spectroscopic measurements showed small but characteristic shifts in the range of 0 ≤ pD ≤ 1, indicative of a triazole
nitrogen atom protonation; the corresponding pK
a of 0.98 ± 0.04 was determined by spectrophotometric titrations. (H2O, 26°C, 1 M KCl/HCl). Formation of [FeIII(La)]+ (pH 2.5) and [FeIII(La)2]− (pH > 6) was verified by UV-Vis spectroscopy. Complex formation of H3Lb with Al3+ and VO2+ was investigated by 1H NMR spectroscopic titration and cyclic voltammetry, respectively. Single crystals of the phenoxo bridged [VVO(HLb)(EtO)]2·2EtOH were characterized by X-ray structural analysis.
Chemical Papers- Slovak Academy of Sciences 04/2012; 62(4):388-397. · 1.10 Impact Factor
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ABSTRACT: In the title mol-ecule, C(9)H(9)N(3)O(9), the three neighbouring nitro groups are tilted with respect to the benzene mean plane by 75.8 (1), 27.7 (1) and 68.1 (1)°. The methyl C atoms of the three neighbouring meth-oxy groups deviate from this plane by 0.976 (4), -1.425 (4) and 0.632 (4) Å. The crystal packing exhibits weak C-H⋯O inter-actions.
Acta Crystallographica Section E Structure Reports Online 03/2012; 68(Pt 3):o694. · 0.35 Impact Factor
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ABSTRACT: In the title mol-ecule, C(6)H(4)N(2)O(7), the two nitro groups are tilted with respect to the aromatic ring by 11.2 (1) and 10.9 (1)°. All three hy-droxy groups are involved in the formation of bifurcated intra- and inter-molecular O-H⋯O hydrogen bonds. The crystal packing exhibits short O⋯O distances of 2.823 (2) Å between two O atoms of the nitro groups.
Acta Crystallographica Section E Structure Reports Online 03/2012; 68(Pt 3):o695. · 0.35 Impact Factor
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ABSTRACT: Metal complex formation of the two cyclic triamines 6-methyl-1,4-diazepan-6-amine (MeL(a)) and all-cis-2,4,6-trimethylcyclohexane-1,3,5-triamine (Me(3)tach) was studied. The structure of the free ligands (H(x)MeL(a))(x+) and H(x)Me(3)tach(x+) (0 ≤ x ≤ 3) was investigated by pH-dependent NMR spectroscopy and X-ray diffraction experiments. The crystal structure of (H(2)Me(3)tach)(p-O(3)S-C(6)H(4)-CH(3))(2) showed a chair conformation with axial nitrogen atoms for the doubly protonated species. In contrast to a previous report, Me(3)tach was found to be a stronger base than the parent cis-cyclohexane-1,3,5-triamine (tach); pK(a)-values of H(3)Me(3)tach(3+) (25 °C, 0.1 M KCl): 5.2, 7.4, 11.2. The crystal structures of (H(3)MeL(a))(BiCl(6))·2H(2)O and (H(3)MeL(a))(ClO(4))Cl(2) exhibited two distinct twisted chair conformations of the seven membered diazepane ring. [Co(MeL(a))(2)](3+) (cis: 1(3+), trans: 2(3+)), trans-[Fe(MeL(a))(2)](3+) (3(3+)), [(MeL(a))ClCd(μ(2)-Cl)](2) (4), trans-[Cu(MeL(a))(2)](2+) (5(2+)), and [Cu(HMeL(a))Br(3)] (6) were characterized by single crystal X-ray analysis of 1(ClO(4))(3)·H(2)O, 2Br(3)·H(2)O, 3(ClO(4))(3)·0.8MeCN·0.2MeOH, 4, 5Br(2)·0.5MeOH, and 6·H(2)O. Formation constants and redox potentials of MeL(a) complexes were determined by potentiometric, spectrophotometric, and cyclovoltammetric measurements. The stability of [M(II)(MeL(a))](2+)-complexes is low. In comparison to the parent 1,4-diazepan-6-amine (L(a)), it is only slightly enhanced. In analogy to L(a), MeL(a) exhibited a pronounced tendency for forming protonated species such as [M(II)(HMeL(a))](3+) or [M(II)(MeL(a))(HMeL(a))](3+) (see 6 as an example). In contrast to MeL(a), Me(3)tach forms [M(II)L](2+) complexes (M = Cu, Zn) of very high stability, and the coordination behavior corresponds mainly to an "all-or-nothing" process. Molecular mechanics calculations showed that the low stability of L(a) and MeL(a) complexes is mainly due to a large amount of torsional strain within the pure chair conformation of the diazepane ring, required for tridentate coordination. This behavior is quite contrary to Me(3)tach and tacn (tacn =1,4,7-triazacyclononane), where the main portion of strain is already preformed in the free ligand, and the amount, generated upon complex formation, is comparably low.
Inorganic Chemistry 10/2010; 49(21):10092-107. · 4.60 Impact Factor
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ABSTRACT: The hexadentate ligand all-cis-N(1),N(2)-bis(2,4,6-trihydroxy-3,5-diaminocyclohexyl)ethane-1,2-diamine (L(e)) was synthesized in five steps with an overall yield of 39% by using [Ni(taci)(2)]SO(4).4H(2)O as starting material (taci=1,3,5-triamino-1,3,5-trideoxy-cis-inositol). Crystal structures of [Na(0.5)(H(6)L(e))](BiCl(6))(2)Cl(0.5).4H(2)O (1), [Ni(L(e))]Cl(2).5H(2)O (2), [Cu(L(e))](ClO(4))(2).H(2)O (3), [Zn(L(e))]CO(3).7H(2)O (4), [Co(L(e))](ClO(4))(3) (5c), and [Ga(H(-2)L(e))]NO(3).2H(2)O (6) are reported. The Na complex 1 exhibited a chain structure with the Na(+) cations bonded to three hydroxy groups of one taci subunit of the fully protonated H(6)(L(e))(6+) ligand. In 2, 3, 4, and 5c, a mononuclear hexaamine coordination was found. In the Ga complex 6, a mononuclear hexadentate coordination was also observed, but the metal binding occurred through four amino groups and two alkoxo groups of the doubly deprotonated H(-2)(L(e))(2-). The steric strain within the molecular framework of various M(L(e)) isomers was analyzed by means of molecular mechanics calculations. The formation of complexes of L(e) with Mn(II), Cu(II), Zn(II), and Cd(II) was investigated in aqueous solution by using potentiometric and spectrophotometric titration experiments. Extended equilibrium systems comprising a large number of species were observed, such as [M(L(e))](2+), protonated complexes [MH(z)(L(e))](2+z) and oligonuclear aggregates. The pK(a) values of H(6)(L(e))(6+) (25 degrees C, mu=0.10 M) were found to be 2.99, 5.63, 6.72, 7.38, 8.37, and 9.07, and the determined formation constants (log beta) of [M(L(e))](2+) were 6.13(3) (Mn(II)), 20.11(2) (Cu(II)), 13.60(2) (Zn(II)), and 10.43(2) (Cd(II)). The redox potentials (vs. NHE) of the [M(L(e))](3+/2+) couples were elucidated for Co (-0.38 V) and Ni (+0.90 V) by cyclic voltammetry.
Chemistry 02/2010; 16(11):3326-40. · 5.93 Impact Factor
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ABSTRACT: The crystal structure of the title compound, [Rh(C(6)H(19)N(4))Cl(3)]Cl·0.5H(2)O, is isotypic with the previously reported Ru analogue. The structure contains two crystallographically independent [Rh(Htren)Cl(3)](+) cations with a facial tridentate coordination of the monoprotonated tren ligand [tren = tris-(2-amino-eth-yl)amine], leading to an overall distorted octahedral coordination environment around the Rh(III) atom. In one of the two cations, the ethyl-ene groups of the two chelate rings as well as the non-coordinating ethyl-ammonium group are disordered over two sets of sites [0.579 (3):0.421 (3) occupancy ratio]. A series of N-H⋯Cl and O-H⋯Cl hydrogen bonds stabilizes the structure.
Acta Crystallographica Section E Structure Reports Online 01/2010; 67(Pt 1):m92-3. · 0.35 Impact Factor
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ABSTRACT: The recently observed nonintuitive pH dependence of methylene (1)H chemical shifts in cobalt(III) polyamine complexes upon deprotonation of coordinated aqua or (poly)alcohol coligands (J. Am. Chem. Soc. 2004, 126, 6728) was attributed to differential spin-orbit effects on the (1)H shifts transmitted over three bonds from the cobalt low-spin d(6) center. These remarkably large spin-orbit effects due to the comparably light Co center have now been examined closely by comparative computations for homologous Rh and Ir complexes, as well as by NMR titrations for a Rh complex. While larger spin-orbit effects (proportional to Z(2)) would have been expected for the heavier metal centers, the characteristic (1)H deshieldings upon deprotonation of [Rh(tren)(OH(2))(2)](3+) [tren = tris(2-aminoethyl)-amine] turn out to be smaller than for the Co homologous Co complex. Systematic computational studies ranging from smaller models to the full complexes confirm these results and extend them to the Ir homologues. Closer analysis indicates that the spin-orbit shift contributions do not follow the expected Z(2) behavior but are modulated dramatically by increasing energy denominators in the perturbation expressions. This is related to the increasing ligand-field splitting from 3d to 4d to 5d system, leading to almost identical differential spin-orbit shifts for the Co and Rh complexes and to only moderately larger effects for the Ir complex (by a factor of about two). Moreover, the differential nonspin-orbit deprotonation shifts cancel the spin-orbit induced contributions largely in the Rh complex, leading to the experimentally observed inverted behavior. The full multidentate polyamine complexes studied experimentally exhibit different three- and four-bond Fermi-contact pathways for transmission of the spin-orbit (1)H shifts. The novel four-bond pathways have different conformational dependencies than the Karplus-like three-bond pathways established previously. Both types of contributions are of similar magnitude. The (1)H NMR deprotonation shift patterns of [Ir(tren)(OH(2))(2)](3+) have been predicted computationally.
Journal of the American Chemical Society 09/2009; 131(33):11909-18. · 9.91 Impact Factor
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ABSTRACT: The crystal structure of the title compound, [Bi(3)(C(6)H(12)N(3)O(3))(2)]Cl(3).6H(2)O, which was described in the space group R3 [Hegetschweiler, Ghisletta & Gramlich (1993). Inorg. Chem. 32, 2699-2704], has been redetermined in the revised space group R32 as suggested by Marsh [Acta Cryst. (2002), B58, 893-899]. Accordingly, the significant difference in the Bi-N bond distances of 2.43 (2) and 2.71 (1) A, as noted in the previous study, proved to be an artifact. As a consequence, the [Bi(3)(H(-3)taci)(2)]Cl(6/3) entity (taci is 1,3,5-triamino-1,3,5-trideoxy-cis-inositol) adopts D(3) symmetry and the three Bi atoms lie on C(2) axes with equal Bi-N bond distances of 2.636 (3) A.
Acta crystallographica. Section C, Crystal structure communications 02/2009; 65(Pt 1):m1-3. · 0.78 Impact Factor
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ABSTRACT: Inclusion compounds of cationic, anionic, and neutral p-substituted derivatives of tert-butylbenzene complexed in beta-cyclodextrin and its ionic 6-mono and 6-hepta derivatives were systematically investigated by isothermal titration calorimetry (ITC). All inclusion compounds showed 1:1 stoichiometry with binding constants ranging from 10 to 3 x 10(6) M(-1). The binding free energies could be subdivided into apolar and electrostatic contributions. The electrostatic interactions could be quantitatively described by Coulomb's law by taking into account the degree of protonation of hosts and guests, the orientations of the guests within the hosts, and ion shielding as described by the Debye-Hückel-Onsager theory. The orientations of the guests within the cyclodextrin cavities were determined by ROESY NMR spectroscopy.
Chemistry 08/2008; 14(24):7202-11. · 5.93 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 11/2007; 2008(1):129 - 137. · 2.94 Impact Factor
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ABSTRACT: The complex formation of vanadium(IV) with cis-inositol (ino) and the corresponding trimethyl ether 1,3,5-trideoxy-1,3,5-trimethoxy-cis-inositol (tmci) was studied in aqueous solution and in the solid-state. With increasing pH, the formation of [VO(H-2L)], [(VO)2L2H-5]-, [VO(H-3L)]- (L = ino) or [(VO)2L2H-6]2- (L = tmci), [V(H-3L)2]2-, and [VO(H-3L)(OH)2]3- was observed. For the vanadium(IV)/ino system, [(VO)2L2H-7]3- was observed as an additional dinuclear species. The formation constants of these complexes were determined by potentiometric titrations (25 degrees C, 0.1 M KCl). In addition, the vanadium(IV)/ino system was investigated by means of UV-vis spectrophotometric methods. EPR spectroscopy and cyclic voltammetry confirmed this complexation scheme. EPR measurements indicated the formation of three distinct isomers of the non-oxo complex [V(H-3ino)2]2- in weakly basic solution. This type of isomerism, which is not observed for the vanadium(IV)/tmci system, was assigned to the ability of ino to bind the vanadium(IV) center with three alkoxo groups having either a 1,3,5-triaxial or an 1,2,3-axial-equatorial-axial arrangement. The structures of [V(H-3ino)2][K2(ino)2].4H2O (1) and [Na6V(H-3ino)2](SO4)2.6H2O (2) were determined by single-crystal X-ray analysis. In both compounds, the coordination of each ino molecule to the vanadium(IV) center via three axial deprotonated oxygen donors was confirmed. The centrosymmetric structure of the coordination spheres corresponds to an almost regular octahedral geometry with a twist angle of 60 degrees. The crystal structure of the potassium complex 1 represents an unusual 1:1 packing of [V(H-3ino)2]2- dianions and [K2(ino)2]2+ dications, in which both K+ ions have a coordination number of nine and are bonded simultaneously to a 1,3,5-triaxial and an 1,2,3-axial-equatorial-axial site of ino. In 2, the [V(H-3ino)2]2- complexes are surrounded by six Na+ counterions that are bonded to the axial alkoxo oxygens and to the equatorial hydroxy oxygens of the cis-inositolato moieties. The six Na+ centers are further interlinked by bridging sulfate ions. According to EPR spectroscopy, the D3d symmetric structure of the [V(H-3ino)2]2- anion is retained in H2O, in dimethylformamide, and in a mixture of CHCl3/toluene 60:40 v/v.
Inorganic Chemistry 06/2007; 46(10):3903-15. · 4.60 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 05/2006; 2006(14):2792 - 2807. · 2.94 Impact Factor
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ABSTRACT: The pH-dependent water-exchange rates of [(CO)2(NO)Re(H2O(cis))2(H2O(trans))]2+ (1) in aqueous media were investigated by means of 17O NMR spectroscopy at 298 K. Because of the low pK(a) value found for 1 (pK(a) = 1.4 +/- 0.3), the water-exchange rate constant k(obs)(H2O(trans/cis)) was analyzed with a two-pathway model in which k(Re)(H2O(trans/cis)) and k(ReOH)(H2O)(trans/cis)) denote the water-exchange rate constants in trans or cis position to the nitrosyl ligand on 1 and on the monohydroxo species [(CO)2(NO)Re(H2O)2(OH)]+ (2), respectively. Whereas the rate constants k(ReOH)(H2O)(trans)) and k(ReOH)(H2O)(cis)) were determined as (4.2 +/- 2) x 10(-3) s(-1) and (5.8 +/- 2) x 10(-4) s(-1), respectively, k(Re)(H2O)(trans)) and k(Re)(H2O)(cis)) were too small to be determined in the presence of the much more reactive species 2. Apart from the water exchange, an unexpectedly fast C identical with 16O --> C identical withO exchange was also observed via NMR and IR spectroscopy. It was found to proceed through 1 and 2, with rate constants k(Re)(CO) and k(ReOH)(CO) of (19 +/- 4) x 10(-3) s(-1) and (4 +/- 3) x 10(-3) s(-1), respectively. On the other hand, N identical with 16O --> N identical with *O exchange was not observed.
Inorganic Chemistry 05/2006; 45(10):4199-204. · 4.60 Impact Factor
