TY - JOUR
T1 - 207pb NMR, Mass Spectrometric, and Electrochemical Studies on Labile Lead(II) Dithiocarbamate Complexes
T2 - Formation of Mixed Mercury-Lead Complexes at a Mercury Electrode in Dichloromethane Solution
AU - Bond, Alan M.
AU - Hollenkamp, Anthony F.
AU - Colton, Ray
PY - 1990/5/1
Y1 - 1990/5/1
N2 - 207Pb NMR spectra have been observed in dichloromethane for series of Pb(RR′dtc)2 compounds (RR′dtc = dialkylthiocarbamate). The resonances are rather broad, and molecular weight determinations show that this is caused by polymerization reactions. Ligand exchange between different Pb(RR′dtc)2 compounds is fast on the NMR time scale, and the complexes are therefore labile. The labile nature of the Pb(RR′dtc)2 systems in the solid state is confirmed by mass spectrometric measurements on mixtures of different complexes. Electrochemical reduction of Pb(RR′dtc)2 in dichloromethane (0.1 M Bu4NClO4) at mercury electrodes takes place in a single reversible two-electron step to give lead amalgam and free [RR′dtc]−, the reversibility of this process further confirming the lability of the complexes. At platinum electrodes, initially an irreversible reduction occurs to generate elemental lead and [RR′dtc]−. However, long-term behavior at platinum electrodes is complicated by the gradual coating of the electrode with elemental lead, thereby generating a lead electrode at which reversible responses are observed. Electrochemical oxidation processes at mercury electrodes are best described in terms of oxidation of the electrode in the presence of Pb(RR′dtc)2. There are three oxidation steps; the product of the first oxidation step is a labile mixed mercury-lead species [HgPb2(RR′dtc)4]2+, which is fully characterized in solution. Attempted isolation of the mixed-metal complex causes ligand redistribution, and [Hg5(RR′dtc)8](ClO4)2, Pb(RR′dtc)2, and Pb(ClO4)2 are produced in the solid state. Controlled-potential electrolysis at the potential of the second oxidation process produces the known [Hg3(RR′dtc)4]2+ species in solution. The electrochemistry in solution and the nature of the isolated products in the solid state indicate that when mercury and lead are competing for dithiocarbamate in a ligand deficient situation, then mercury is the successful element.
AB - 207Pb NMR spectra have been observed in dichloromethane for series of Pb(RR′dtc)2 compounds (RR′dtc = dialkylthiocarbamate). The resonances are rather broad, and molecular weight determinations show that this is caused by polymerization reactions. Ligand exchange between different Pb(RR′dtc)2 compounds is fast on the NMR time scale, and the complexes are therefore labile. The labile nature of the Pb(RR′dtc)2 systems in the solid state is confirmed by mass spectrometric measurements on mixtures of different complexes. Electrochemical reduction of Pb(RR′dtc)2 in dichloromethane (0.1 M Bu4NClO4) at mercury electrodes takes place in a single reversible two-electron step to give lead amalgam and free [RR′dtc]−, the reversibility of this process further confirming the lability of the complexes. At platinum electrodes, initially an irreversible reduction occurs to generate elemental lead and [RR′dtc]−. However, long-term behavior at platinum electrodes is complicated by the gradual coating of the electrode with elemental lead, thereby generating a lead electrode at which reversible responses are observed. Electrochemical oxidation processes at mercury electrodes are best described in terms of oxidation of the electrode in the presence of Pb(RR′dtc)2. There are three oxidation steps; the product of the first oxidation step is a labile mixed mercury-lead species [HgPb2(RR′dtc)4]2+, which is fully characterized in solution. Attempted isolation of the mixed-metal complex causes ligand redistribution, and [Hg5(RR′dtc)8](ClO4)2, Pb(RR′dtc)2, and Pb(ClO4)2 are produced in the solid state. Controlled-potential electrolysis at the potential of the second oxidation process produces the known [Hg3(RR′dtc)4]2+ species in solution. The electrochemistry in solution and the nature of the isolated products in the solid state indicate that when mercury and lead are competing for dithiocarbamate in a ligand deficient situation, then mercury is the successful element.
UR - http://www.scopus.com/inward/record.url?scp=26744465448&partnerID=8YFLogxK
U2 - 10.1021/ic00335a043
DO - 10.1021/ic00335a043
M3 - Article
AN - SCOPUS:26744465448
SN - 0020-1669
VL - 29
SP - 1991
EP - 1995
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 10
ER -