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Electrochemistry of Some Rhodium(I) Complexes


Najdzionek, Jan Stanley (1982) Electrochemistry of Some Rhodium(I) Complexes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/pqye-xp04.


The electrochemistry of Rh[C6H5)2P(CHx)nP(C6H5)2]2 Y where Y = CF3SO-3 or ClO-4, x = 2 with n = 1, 2, 3, 4 and x = 1 with n = 2 was examined and compared with that of Co[(C6H5)2P(CHx)2P(C6H5)2]2 where x = 1 and 2. Cyclic voltammetric (CV), chronoamperometric (CA), polarographic (including D.C., normal and differential pulse) and bulk electrolytic experiments were performed and the results show that all of these Rh(I) phosphine complexes are reduced in a two-electron process.

CV and CA measurements were used to determine the heterogeneous electron transfer rate constants for Rh[(C6H5)2P(CH2)2P(C6H5)2]2. The values determined were 0.0092 and 0.0087 cm/sec, respectively, and the results are discussed in relation to the Butler-Volmer formulation of electrode kinetics.

Fluorescence measurements were made on the above rhodium complexes for n = 1, 3 and 4 at room temperature and at 77 K. None emit under ambient conditions in solution but the compound containing ligands with a single methylene unit backbone emitted at 77 K with a lifetime of 20 microseconds. The UV-Visible spectrum of reduced Rh(DPP)+2, the most stable of the reduced complexes, displayed a very intense absorption at 450 nm which was assumed to be charge-transfer in origin.

The two-electron reduction of Rh2(2,5-dimethyl-2,5-diisocyanohexane)2+4 produced a unique species in which a CN- ion has been lost resulting in the formation of a cyclohexylimine ligand which bridges the metal atoms through the imine function. The strain imposed on the TMB ligand backbone forces the rhodium atoms to have the strongest interaction of any of the Rh(Br)+4 compounds studied [Rh(l)-Rh(2) = 2.970(1)Å]. Linear isocyanide carbon-nitrogen distances range from 1.153(9) to 1.175(9) Å while the imine carbon-nitrogen is extended slightly to 1.254(9) Å.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Collins, Terrence J.
Thesis Committee:
  • Anson, Fred C. (chair)
  • Gray, Harry B.
  • Janda, Kenneth C.
  • Dervan, Peter B.
  • Collins, Terrence J.
Defense Date:27 August 1981
Record Number:CaltechTHESIS:07132018-094917474
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11122
Deposited By: Mel Ray
Deposited On:13 Jul 2018 20:06
Last Modified:16 Apr 2021 23:16

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