TY - JOUR
T1 - Dinuclear oxomolybdate(v) species with oxalato and pyridine ligands revisited
T2 - cis/trans isomerization of [Mo2O4(η 2-C2O4)2(R-Py)2] 2- (R-Py = pyridine, alkyl-substituted pyridine) in water evidenced by NMR spectroscopy
AU - Modec, Barbara
AU - Dolenc, Darko
AU - Brenčič, Jurij V.
AU - Koller, Jože
AU - Zubieta, Jon
PY - 2005/8/19
Y1 - 2005/8/19
N2 - The simple oxohalomolybdate(V) ions [MoOCl4(H 2O)]- and [MoOBr4]- were reacted with oxalic acid in mixtures containing an alcohol and a pyridine (R-Py) to form the dinuclear anions [Mo2O4(η2-C 2O4)2(R-Py)2)2] 2- based on the {Mo2O4}2+ structural core. The dinuclear anion exists in two isomeric forms - as a trans and as a cis isomer. A trans arrangement of the pyridine ligands relative to the Mo 2(μ2-O)2 bridge was observed for (PyH) 2[Mo2O4(η2-C2O 4)2Py2] (1), (PyH)2-[Mo 2O4(η2-C2O4) 2(3,5-Lut)2] (2), [MeNC5H3(Me) 2]2[Mo2O4-(η2-C 2O4)2(3,5-Lut)2]·H 2O (3), (4-MePyH)2[Mo2O4(η 2-C2O4)2-(4-MePy) 2]·1/2(4-MePy) (5), and [(C6H5) 4P]2[Mo2O4(η2-C 2O4)2-Py2]·H2O (7) [Py = pyridine; 3,5-Lut = 3,5-lutidine; MeNC5H3(Me) 2+ = N-methyl-3,5-lutidinium cation and 4-MePy = 4-methylpyridine], while a cis arrangement was found in only two compounds, namely (4-EtPyH)2[Mo2O4(η2- C2O4)2(4-EtPy)2] (4) (4-EtPy = 4-ethylpyridine) and (4-MePyH)3[Mo2O4(η 2-C2O4)2(4-MePy)2]Br (6). The solution chemistry of the trans-[Mo2O4(η 2-C2O4)2Py2] 2- anion was monitored by 1H and 13C variable temperature NMR spectroscopy and showed evidence of two processes: the substitution of a pyridine ligand for water, coupled with cis/trans isomerization. Both reactions were exploited in the preparation of trans-(PyH)2[Mo2O4(η2-C 2O4)2(H2O)2] (8) from a water/methanol solution of cis-(4-EtPyH)2[Mo2O 4(η2-C2O4)2(4-EtPy) 2] (4). trans-(PyH)2[Mo2O4(η 2-C2O4)2(H2O) 2] (8) was seen to react with methanol with the rupture of the molybdenum-to-oxalate bonds resulting in the cyclic octanuclear anion which crystallizes as a pyridinium salt, (PyH)2[Mo8O 16(OCH3)8(μ8-C2O 4)]·2CH3OH (9). The compounds were fully characterized by X-ray structural analysis and IR spectroscopy. MO calculations were performed on the isomeric pair of [Mo2O4(η 2-C2O4)2(4-MePy)2] 2- in order to establish their relative energies.
AB - The simple oxohalomolybdate(V) ions [MoOCl4(H 2O)]- and [MoOBr4]- were reacted with oxalic acid in mixtures containing an alcohol and a pyridine (R-Py) to form the dinuclear anions [Mo2O4(η2-C 2O4)2(R-Py)2)2] 2- based on the {Mo2O4}2+ structural core. The dinuclear anion exists in two isomeric forms - as a trans and as a cis isomer. A trans arrangement of the pyridine ligands relative to the Mo 2(μ2-O)2 bridge was observed for (PyH) 2[Mo2O4(η2-C2O 4)2Py2] (1), (PyH)2-[Mo 2O4(η2-C2O4) 2(3,5-Lut)2] (2), [MeNC5H3(Me) 2]2[Mo2O4-(η2-C 2O4)2(3,5-Lut)2]·H 2O (3), (4-MePyH)2[Mo2O4(η 2-C2O4)2-(4-MePy) 2]·1/2(4-MePy) (5), and [(C6H5) 4P]2[Mo2O4(η2-C 2O4)2-Py2]·H2O (7) [Py = pyridine; 3,5-Lut = 3,5-lutidine; MeNC5H3(Me) 2+ = N-methyl-3,5-lutidinium cation and 4-MePy = 4-methylpyridine], while a cis arrangement was found in only two compounds, namely (4-EtPyH)2[Mo2O4(η2- C2O4)2(4-EtPy)2] (4) (4-EtPy = 4-ethylpyridine) and (4-MePyH)3[Mo2O4(η 2-C2O4)2(4-MePy)2]Br (6). The solution chemistry of the trans-[Mo2O4(η 2-C2O4)2Py2] 2- anion was monitored by 1H and 13C variable temperature NMR spectroscopy and showed evidence of two processes: the substitution of a pyridine ligand for water, coupled with cis/trans isomerization. Both reactions were exploited in the preparation of trans-(PyH)2[Mo2O4(η2-C 2O4)2(H2O)2] (8) from a water/methanol solution of cis-(4-EtPyH)2[Mo2O 4(η2-C2O4)2(4-EtPy) 2] (4). trans-(PyH)2[Mo2O4(η 2-C2O4)2(H2O) 2] (8) was seen to react with methanol with the rupture of the molybdenum-to-oxalate bonds resulting in the cyclic octanuclear anion which crystallizes as a pyridinium salt, (PyH)2[Mo8O 16(OCH3)8(μ8-C2O 4)]·2CH3OH (9). The compounds were fully characterized by X-ray structural analysis and IR spectroscopy. MO calculations were performed on the isomeric pair of [Mo2O4(η 2-C2O4)2(4-MePy)2] 2- in order to establish their relative energies.
KW - Isomerization
KW - Molybdenum
KW - N ligands
KW - NMR spectroscopy
KW - Polyoxometalates
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U2 - 10.1002/ejic.200500023
DO - 10.1002/ejic.200500023
M3 - Article
AN - SCOPUS:23944510449
SN - 1434-1948
SP - 3224
EP - 3237
JO - European Journal of Inorganic Chemistry
JF - European Journal of Inorganic Chemistry
IS - 16
ER -