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Syntheses, characterizations and reactivity of trans-dioxorhenium(V) and -(VI) complexes

Citation

Brewer, John C. (1991) Syntheses, characterizations and reactivity of trans-dioxorhenium(V) and -(VI) complexes. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-06142007-144656

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The synthesis, electronic structure and reactivity of trans-dioxorhenium(V) and -(VI) complexes have been examined in detail. An improved general synthesis of trans-[ReO2(L)4]X complexes is presented. The amine complex [ReO2(en)2]I can be made in 90% yield from ReO2(PPh3)2I and ethylenediamine in less than 15 minutes at room temperature. Refluxing methanol suspensions of ReO2(PPh3)2I with 12-50 equivalents of electron-rich pyridines results in the formation of [ReO2L4]I compounds in 50 to 85% yield. Systematic substituent studies reveal the influence of ancillary ligands on the physical properties of trans-[ReO2(L)4][PF6] compounds. The Re(VI)/Re(V) redox couple is a linear function of pyridine ligand [...] (ReVI/Re/V) = (0.96 + [...]) V vs. Fc+/Fc. The dxy/dxz,dyz energy gap is also a linear function of pyridine [...]; increasing the pyridine basicity lowers the energy of the dxy [...] dxz,dyz transition and the energy of the [...] excited state. The excited-state properties of trans-[ReO2(L)4][PF6] pyridine complexes follow a trend consistent with the energy-gap law. Strongly basic 4-dialkylaminopyridine ligands stabilize d(1) trans-dioxorhenium(VI) complexes. Analysis of the X-ray structure of trans-[...] shows that there is considerable shortening (0.04 A) in the Re-N bond lengths relative to Re(V) analogues, but the Re-oxo bond lengths are virtually the same in both oxidation states. The EPR spectrum of the d(1) ion trans-[...] (dmap = 4-dimethylaminopyridine) has been measured in a 50% DMSO/H2O glass at 7 K. Analysis of the spectrum gives g[...] = 1.91, A[...] = 0.031 cm(-1), g|| = 1.83, A|| = 0.060 cm(-1), and Qz = 0.0075 cm(-1). Because of the large quadrupole coupling, the forbidden ([...] = ±1, ±2) transitions are quite intense and some are stronger than the allowed ([...] = 0) transitions. Comparison of Qz values and dxy [...] dxz,dyz transition energies for trans-[reO2(dmap)4](2+) and related monooxo and mononitrido complexes confirms that the ligand-field splitting associated with the multiply bonded units increases in the order ReO(4+) < ReN(3+) < ReO2(2+).

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Awards:The Herbert Newby McCoy Award, 1990
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Gray, Harry B.
Thesis Committee:
  • Unknown, Unknown
Defense Date:17 October 1990
Record Number:CaltechETD:etd-06142007-144656
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-06142007-144656
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2598
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:10 Jul 2007
Last Modified:26 Dec 2012 02:52

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