IDENTIFICATION OF AN EXTENSIVE SERIES OF CATIONIC SILVER HETEROMETALLIC DITHIOCARBAMATE COMPLEXES AND OBSERVATION OF CATALYTIC LIGAND-EXCHANGE REACTIONS BY ELECTROSPRAY MASS-SPECTROMETRY

The metal-metal-bonded cations [Ag2Pt3(R2dtc)6]2+, consisting of Pt(R2 dtc)2 units acting as ligands toward Ag(I), are observed in electrospr ay mass spectra as intact ions and also as the monoanion adducts [Ag2P t3(R2dtc)6X]+ (X- = ClO4-, NO3-). When solutions containing two differ ent Pt(R2dtc)2 complexes and Ag(I) are mixed, there is global scrambli ng of dithiocarbamate ligands on platinum in the Ag/Pt/R2dtc cations w ithin 1 h, which is much faster than exchange in the absence of Ag(I). Hg(R2dtc)2 complexes also act as ligands toward Ag(I), and the cation s [AgHg2(R2dtc)4]+ are readily observed. Mixtures of two different Hg( R2dtc)2 complexes with Ag(I) give the expected global scrambling of th e dithiocarbamates on mercury. Interaction between M(R2dtc)3 (M = Co, Rh, Ir) and Ag(I) leads to the observation of [AgM2(R2dtc)6]+ cations, and mixing of different M(R2dtc)3 compounds with Ag(I) leads to excha nge of complete M(R2dtc)3 units on Ag but not global dithiocarbamate l igand exchange on cobalt. However, fast global exchange of dithiocarba mate ligands on cobalt and mercury, as well as interchange of metals t o give trimetallic species containing Ag, Co, and Hg, is observed when mixtures of Co(R2dtc)3, Hg(R'2dtc)2, and Ag(I) are examined by ESMS. Similar global ligand exchange does not occur when Rh(R2dtc)3 or Ir(R2 dtc)3 is mixed with Hg(R'2dtC)2 and Ag(I), although exchange of comple te metal dithiocarbamate units on Ag(I) does still occur to give mixed Ag/Rh/Hg cations. Sulfur insertion occurs with the iridium complexes to give [AgIr2(R2dtc)5(R2dtcS)]+ and AgIr2(R2dtc)4(R2dtcS)2]+. These r esults indicate that an extensive new chemistry of neutral metal dithi ocarbamates exists in which they behave as ligands toward metal cation s. Reaction of silver salts with the dithiocarbamates of Zn(II) and Pb (II) leads to formation of non-silver-containing metal-rich dithiocarb amate cations of the types [M2(R2dtc)3]+ and [M2(R2dtc)5]+(M=Zn,Pb). S ilver(I) salts simply oxidize the dithiocarbamates of Fe(III) and Ni(I I) to give the known [Fe(R2dtc)3]+ and [Ni(R2dtc)3]+ species.