COMPARISON OF THE [MIV(RR'DTC)3]+/MIII(RR'DTC)3 AND [MIV(ET2DSC)3]+/MIII(ET2DSC)3 (M = CO, RH, IR DTC = DITHIOCARBAMATE DSC = DISELENOCARBAMATE) REDOX COUPLES THE REACTIVITY OF THE OXIDATION-STATE IV COMPLEXES IN SOLUTION AND IN THE GAS-PHASE AS STUDIED BY ELECTROCHEMICAL AND MASS-SPECTROMETRIC TECHNIQUES

被引:46
作者
BOND, AM [1 ]
COLTON, R [1 ]
MANN, DR [1 ]
机构
[1] UNIV MELBOURNE,DEPT INORGAN CHEM,PARKVILLE,VIC 3052,AUSTRALIA
关键词
D O I
10.1021/ic00348a016
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
A range of IrIII(RR′dtc)3complexes (RR′dtc = dithiocarbamate) and IrIII(Et2dsc)3(dsc = diselenocarbamate) have been synthesized. The [IrIV(RR′dtc)3]+and [IrIV(Et2dsc)3]+oxidized species have been prepared and studied in solution by electrochemical techniques and in the gas phase by mass spectrometry. Voltammetric studies at platinum disk electrodes in dichloromethane, acetone, and acetonitrile enable the standard redox potentials (E°) for the [Ir(RRE′dtc)3]+/Ir(RR′dtc)3couple (and the selenium analogue) to be calculated from the chemically reversible one-electron-oxidation process Ir(RR′dtc)3⇌ [Ir(RR′dtc)3]++ e−. Comparison with data for the corresponding cobalt and rhodium complexes shows the E° values to have the unexpected order Rh > Co > Ir with the rhodium couple being the most positive. Bulk electrolysis at platinum-gauze electrodes enables the Ir(IV) complexes to be characterized in dichloromethane solution. [Ir(RR′dtc)3]+is stable on the synthetic time scale whereas [Ir(Et2dsc)3]+slowly dimerizes during the course of bulk electrolysis experiments and subsequently undergoes an internal redox reaction to give [Ir2(Et2dsc)5]+and oxidized ligand, as previously observed for cobalt and rhodium dithiocarbamate and diselenocarbamate complexes. The order of the rates of these redox-based decomposition reactions is Rh » Co » Ir, which leads to the unusual result that Rh(IV) is considerably more reactive than Co(IV), with the high stability of Ir(IV) being as expected. That is, in this case, the thermodynamic and kinetic stabilities are parallel. The strong oxidizing power of the [Ir(RR′dtc)3]+cations is illustrated by their oxidation of free dithiocarbamate ion to give thiuram disulfide and by the oxidation of elemental mercury to give mixed-metal complexes Hg + 2[Ir(RR′dtc)3]+→ [HgIr2(RR′dtc)6]2+. The mixed mercury/iridium complexes are also generated electrochemically at mercury electrodes by the reversible process Hg + 2Ir(RR′dtc)3⇌ [HgIr2(RR′dtc)6]2++ 2e−. Generation of [M(RR′dtc)3]+(M = Co, Rh, Ir) in the gas phase by positive ion mass spectrometry reveals the expected order of reactivity Ir < Rh < Co. The differences between the solution and gas-phase reactivities of the oxidation state IV complexes are explained by the presence of dimerization reactions in solution, which cannot occur under the conditions of mass spectrometry. © 1990, American Chemical Society. All rights reserved.
引用
收藏
页码:4665 / 4671
页数:7
相关论文
共 35 条