H Nuclear Magnetic Resonance Evidence for the Pseudo-octahedral

Citation:
URBAC FL, WANDIGA S 0. "H Nuclear Magnetic Resonance Evidence for the Pseudo-octahedral.". 1970;1572.

Abstract:

Summary From lH n.m.r. studies the trigonal hexadentate complex, [ 1,1,l-tris(pyridine-2-carboxaldiminornethy-l ) ethane]iron(~~is) ,s hown to possess a pseudo-octahedral geometry and to racemize readily.
M-E report here the observation of raceniization of the pseudo-octahedral complex [ lI1,l-tris(pyridine-2-carboxaldiminomethyl) ethane]iron( 11), [Fe(py,tame)I2+, as deduced from the lH n.m.r. behaviour of the diastereotopic methylene protons. The complex, synthesizcd by the literature niethod,l was isolated as red-purple crystals having the stoicheiometry Fe(py3tame)C1,,2H,O. The lH n.m.r. spectrum of [Fe(py,tame)I2+ in D,O was measured with a Varian HA-100 MHz spectrometer with sodium 3-(trimethylsilyl)propane-l-sulphonatea s an internal reference. The observation of one resonance (6 9.26 p.p.m.) for the azomethine protons and a single set of resonances for the pyridine protons (6 7-50, 7.70, 8.24, and 8-41 p.p.m.) confirms the hexadentate co-ordination of the intact Schiff -base iigand. At 25” the methylene protons exhibit an AB pattern with 6, 3.99, 6b 4.12 p.p.m., and Jab 14 Hz. This diastereotopic behaviour of the methylene protons could only arise from a chiral, pseudo-octahedral geometry of the complex.

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