I. The Heptacyanomolybdate(III) Ion: Spectroscopic and Magnetic Properties and Chemical Reactivity. II. Spectroscopic and Magnetic Studies of Monomeric and Dimeric d⁵ Systems. III. Spectroscopic and Magnetic Studies of Polymeric Oxo- and Hydroxobridged Systems

Citation

Rossman, George Robert (1971) I. The Heptacyanomolybdate(III) Ion: Spectroscopic and Magnetic Properties and Chemical Reactivity. II. Spectroscopic and Magnetic Studies of Monomeric and Dimeric d⁵ Systems. III. Spectroscopic and Magnetic Studies of Polymeric Oxo- and Hydroxobridged Systems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/JZTQ-Q938. https://resolver.caltech.edu/CaltechTHESIS:12202016-092448657

Abstract

Heptacyanomolybdate(III), isolated as the potassium salt, K₄Mo(CN)₇ · 2H₂O has been studied by infrared, raman, ESR, magnetic susceptibility, optical spectral, and x-ray techniques. Solutions of the ion have been identified as having a seven-coordinate pentagonal bipyramidal structure, while the structure in the solid potassium salt has been proposed to be a capped trigonal prism. The anhydrous potassium salt, K₄Mo(CN)₇, and the hydrated cesium salt, Cs₄Mo(CN)₇ · xH₂O also assume the pentagonal bi pyramidal geometry. The molecule is chemically reactive, combining readily in solution with oxygen to form [Mo(CN)₇OH₂]^4- and with halogens to form products which when isolated are waxy and presumably polymeric.

Optical spectra have been obtained for four-, five-, six-, and seven-coordinate manganese(II) and iron(III) compounds. These are used as a basis of comparison for interpretation of the detailed optical and magnetic data obtained on the oxobridged iron(III) dimer enH₂[(FeHEDT A)₂O] · 6H₂O.

The occurrence of simultaneous pair electronic excitations in the dimer is described, and evaluation of the relative merits of the spin-coupling and molecular orbital models for oxobridged dimers is presented. A dihydroxobridged ferric dimer is described as well as a series of dialkoxobridged iron(m) and aluminum dimers derived from metal acetylacetonate and dipivaloylmetane complexes. The extent of antiferromagnetic coupling between the two iron atoms in the dihydroxo- and the dialkoxobridged iron dimers has been found to be nearly identical through variable temperature magnetic susceptibility studies. The magnetic and infrared studies are extended to include a variety of metal oxides, oxy-hydroxides, and natural and synthetic minerals which have various forms of oxo- and hydroxobridging. The OH infrared bands are identified and in some instances, the LN₂ temperature positions of the band are compared to the room temperature position. Ferritin models and ferritin micelles are compared to these iron polymers, and the similarity of the infrared spectrum of ferric hydroxide to ferritin micelles is discussed.

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