Copper(I), Lithium, and Magnesium Thiolate Complexes: An Overview with Due Mention of Selenolate and Tellurolate Analogues and Related Silver(I) and Gold(I) Species. In: Karlin KD, editor. Progress in Inorganic Chemistry. Hoboken: John Wiley & Sons, Inc.; 1997. pp. 97-149. [DOI: 10.1002/9780470166475.ch2]

Rhodium and Iridium Complexes of Anionic Thione and Selone Ligands Derived from Anionic N-Heterocyclic Carbenes

The lithium salts of anionic N‐heterocyclic thiones and selones [{(WCA‐IDipp)E}Li(toluene)] (1: E=S; 2: E=Se; WCA=B(C₆F₅)₃, IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene), which contain a weakly coordinating anionic (WCA) borate moiety in the imidazole backbone were reacted with Me₃SiCl, to furnish the silylated adducts (WCA‐IDipp)ESiMe₃ (3: E=S; 4: E=Se). The reaction of the latter with [(η⁵‐C₅Me₅)MCl₂]₂ (M=Rh, Ir) afforded the rhodium(III) and iridium(III) half‐sandwich complexes [{(WCA‐IDipp)E}MCl(η⁵‐C₅Me₅)] (5–8). The direct reaction of the lithium salts 1 and 2 with a half or a full equivalent of [M(COD)Cl]₂ (M=Rh, Ir) afforded the monometallic complexes [{(WCA‐IDipp)E}M(COD)] (9–12) or the bimetallic complexes [μ₂‐{(WCA‐IDipp)E}M₂(COD)₂(μ₂‐Cl)] (13–16), respectively. The bonding situation in these complexes has been investigated by means of density functional theory (DFT) calculations, revealing thiolate or selenolate ligand character with negligible metal‐chalcogen π‐interaction.

Dimeric Copper and Lithium Thiolates: Comparison of Copper Thiolates with Their Lithium Congeners

The direct reactions of the large terphenyl thiols HSAr^iPr4 (Ar^iPr4= -C₆H₃-2,6-(C₆H₃-2,6-iPr₂)₂) and HSAr^iPr6 (Ar^iPr6= -C₆H₃-2,6-(C₆H₂-2,4,6-iPr₃)₂) with stoichiometric amounts of mesitylcopper(I) in THF at ca. 80 °C afforded the first well-characterized dimeric copper thiolato species {CuSAr^iPr4}₂ (1) and {CuSAr^iPr6}₂ (2) with elimination of mesitylene. The complexes 1 and 2 were characterized by NMR and electronic spectroscopy as well as by X-ray crystallography. They have dimeric Cu₂S₂ core structures in which the two copper atoms are bridged by the sulfurs from the thiolato ligands and feature short Cu--Cu distances near 2.4 Å as well as a weak copper-flanking aryl ring interaction from a terphenyl substituent. The structures of the planar Cu₂S₂ cores bear a resemblance to the Cu_A site in nitrous oxide reductase in which two cysteines also bridge two copper atoms. The related dimeric Li₂S₂ structural motif was also observed in the lithium congeners {LiSAr^iPr4}₂ (3) and {LiSAr^iPr6}₂ (4) which were synthesized directly from the thiols and n-BuLi in hexanes. However, despite the very similar effective ionic radii of the Li⁺ (0.59 Å) and Cu⁺ (0.60 Å) ions, the Li--Li structures display very much longer (by more than ca. 0.5 Å) separations than the corresponding Cu--Cu distances in 1 and 2, which may be due to weaker dispersion interactions.

Metal complexes of the mycotoxins sporidesmin A and gliotoxin, investigated by electrospray ionisation mass spectrometry

The mycotoxin sporidesmin A (spdA), responsible for the intoxication of animals, causing facial eczema, has been investigated by electrospray ionisation mass spectrometry. Protonated [spdA+H](+) and deprotonated [spdA-H](-) ions are observed in positive and negative ion modes respectively. Reduced spdA, formed by cleavage of the disulfide bond by Na[BH(4)] gives an ion [spdA+H](-), and forms ions of the type [2spdA+M](2-) with a range of divalent metal ions M(2+)=Zn(2+), Cd(2+), Hg(2+), Sn(2+) and Fe(2+). Sodium-containing analogues [2spdA+M+Na](-) are observed, particularly at high cone voltages, where they are stable towards cone voltage-induced fragmentation, indicating appreciable stability of the (spdA)(2)M system. A competition experiment between Cd(2+) and Zn(2+) demonstrates that reduced spdA has a higher affinity for Cd(2+) ions. The related gliotoxin (gtx) forms analogous [2gtx+M](2-) and [2gtx+M+Na](-) ions. The reduction and metal complexation of spdA can be monitored by (1)H NMR spectroscopy, and results in chemical shift changes for those protons adjacent to the sulfur atoms. The isolation of a polymeric cadmium-spdA complex is also reported.