Date of Award
Doctor of Philosophy
Part I. Reactions of (alpha)-hydroxyalkylchromium(III) complexes;A. Acidolysis and homolysis;The reactivity of several pentaaquo-(alpha)-hydroxyalkylchromium(III) complexes including (H(,2)O)(,5)CrCH(C(,2)H(,5))OH('2+), CrC(CH(,3))(C(,2)H(,5))OH('2+), CrC(C(,2)H(,5))(,2)OH('2+), CrC(CH(,3))(i-C(,3)H(,7))OH('2+) and CrC(CH(,3))(t-C(,4)H(,9))OH('2+) was examined. The chromium-carbon bond was found to cleave by both heterolytic and homolytic pathways. The heterolytic pathway, in general termed acidolysis, is the common mode of decomposition of most pentaaquoalkylchromium(III) complexes. The products of acidolysis are such that the reaction may be formally viewed as the protonation of the carbanion bonded to chromium(III). The homolytic pathway was studied through the use of oxidizing scavengers which reacted with the products of homolysis (Cr('2+) and R(.)), but not directly with the alkylchromium(III) complexes. Thus, by proper selection of reaction conditions, rate constants for both pathways were determined. In most cases, the homolysis rate constants were much greater in magnitude than the acidolysis values. The homolysis rate constants were found to be strongly influenced by steric effects. At 25.0(DEGREES)C, the rate constants varied (TURN)10('7) with CrCH(,2)OH('2+) (k(,hom) = 3.7 x 10('-5) s('-1)), the least substituted complex having the slowest homolysis rate and CrC(CH(,3))(t-C(,4)H(,9))OH('2+) (k(,hom) (TURN)3 x 10('2) s('-1)) having the fastest homolysis rate;One (alpha)-alkoxyalkylchromium(III) complex, CrC(CH(,3))(,2)OCH(CH(,3))(,2)('2+), was also studied. This complex was found to have a unique homolysis rate constant (5.77 (+OR-) 0.15 s('-1) at 25.0(DEGREES)C). It was also found to undergo rearrangement in dilute perchloric acid to CrC(CH(,3))(,2)OH('2+). At mechanism analogous to similar acid-catalyzed cleavage of dialkylethers is presented;B. Reactions with Cu('2+) or Fe('3+);The reactions of five alkylchromium(III) complexes with Cu('2+) or Fe('3+) were investigated. The predominant pathway for reactions with both oxidants was found to be inversely dependent on the acid concentration in the range studied. Two different mechanisms are proposed to explain the results obtained. The Cu('2+) reactions occur by binding of Cu('2+) to the (alpha)-hydroxyl oxygen in its basic form. The Fe('3+) reactions probably proceed through attack directly at the chromium center;Part II. Binuclear cobalt complexes of Schiff base macrocyclic ligands;Three dicobalt(II) complexes of Schiff base macrocyclic ligands with N(,2)O(,2) chelating sites were prepared. These complexes were all based upon the tetra(salicylideneamino)benzene unit as shown. The;complexes were characterized by their electronic spectra and elemental analysis. The dicobalt(II) complexes are easily converted to the dicobalt(III) analogs using oxidizing agents such as Co(NH(,3))(,5)Cl('2+), H(,2)O(,2) and O(,2) in methanol solution. The dicobalt(III) complexes may be re-reduced to the parent dicobalt(II) complexes with CrCl(,2). One organometallic derivative, (CH(,3)Co)(,2)(5-Bu('t)sal(,4))bz, was prepared. It was characterized by its reaction with Hg(II) and its photodecomposition to the dicobalt(II) complex under anaerobic conditions and to dicobalt(III) under aerobic conditions;('1)DOE Report IS-T-954. This work was performed under Contract W-7405-eng-82 with the Department of Energy.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Garry Wayne Kirker
Kirker, Garry Wayne, "Mechanistic chemistry of some transition metal complexes " (1981). Retrospective Theses and Dissertations. 7183.