The chemistry of tri- and high-nuclearity palladium(II) and platinum(II) complexes

The one-step synthesis of three new P2O-terdentate carboxylic acid ditertiary phosphines 2-{(Ph2PCH2)2N}-3-(X)C6H3CO2H (X = OCH3, L1; X = OH, L2) and 2-{(Ph2PCH2)2N}-5-(OH)C6H3CO2H (L3) by a phosphorus-based Mannich condensation reaction using Ph2PCH2OH and the appropriate amine in CH3OH is reported. Compounds L1−L3 function as typical κ2-P2-didentate ligands upon complexation to Pd(CH3)Cl(cod) (cod = cycloocta-1,5-diene), affording the neutral, mononuclear complexes Pd(CH3)Cl(L1−L3) (1−3). Metathesis of 1 with NaX (X = Br, I) gave the corresponding (methyl)bromopalladium(II) (4) and (methyl)iodopalladium(II) (5) complexes, respectively. When chloroform or chloroform/methanol solutions of 1−3 (or 5) were allowed to stand, at ambient temperatures, yellow crystalline solids were isolated in very high yields (71−88%) and were analyzed for the novel hexameric palladium(II) compounds 6−9. All new compounds reported have been fully characterized by a combination of spectroscopic (multinuclear NMR, Fourier trans...

Neutral Molecular Pd6 Hexagons Using κ3-P2O-Terdentate Ligands

Trinuclear molybdenum cluster sulfides coordinated to dithiolene ligands and their use in the development of molecular conductors

Mononuclear Zn, Cd, and Hg 1,2-benzenedithiolates with intramolecular NH···S hydrogen bonds, [MII{1,2-S2-3,6-(RCONH)2C6H2}2]2− (R = CH3, t-Bu; M = Zn, Cd, Hg), were synthesized and characterized by X-ray analysis and spectral measurements. The presence of intramolecular NH···S hydrogen bonds was established by the IR spectra. 199Hg and 113Cd nuclear magnetic resonance showed a stabilized four-thiolate coordinated structure and suggested the influence of the NH···S hydrogen bonds to pπ(Hg)−pπ(S) interactions. The NH stretching bands show that the NH···S hydrogen bonds in Cd and Hg complexes are stronger than those in the corresponding Zn complex. These results are supported by theoretical calculations. The experimental and theoretical results suggested that the NH···S hydrogen bond influences the efficient capture of toxic Cd and Hg ions by metallothioneins.

Zinc, cadmium, and mercury 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds.

Reaction of NO2– with the octahedral cluster (HL)2Fe6 in the presence of a proton source affords the hexanitrosyl cluster (HL)2Fe6(NO)6. This species forms via a proton-induced reduction of six nitrite molecules per cluster, utilizing each site available on the polynuclear core. Formation of the hexanitrosyl cluster is accompanied by a near 2-fold expansion of the (HL)2Fe6 core volume, where intracore Fe–Fe interactions are overcome by strong π-bonding between Fe centers and NO ligands. A core volume of this magnitude is rare in octahedral metal clusters not supported by interstitial atoms. Moreover, the structural flexibility afforded by the (HL)2Fe6 platform highlights the potential for other reaction chemistry involving species with metal–ligand multiple bonds. Carrying out the reaction of the cluster [(HL)2Fe6(NCMe)6]4+ with nitrite in the absence of a proton source serves to forestall the nitrite reduction and enables clean isolation of the intermediate hexanitro cluster [(HL)2Fe6(NO2)6]2–.

Multi-site reactivity: reduction of six equivalents of nitrite to give an Fe6(NO)6 cluster with a dramatically expanded octahedral core.

Reaction of a stoichiometric equivalent of the zinc-dithiolene complex, (tmeda)ZnS2C2(COOMe)2 (tmeda = tetramethylethylenediamine), with (MeCN)2PdCl2 results in a 1:1 homoleptic dithiolene that forms the hexanuclear cluster [PdS2C2(COOMe)2]6 (1). X-ray structure analysis of 1 indicates a Pd6S12 core comprised of six face-centered palladium atoms and 12 edge-centered sulfur atoms situated on an imaginary approximate cube. Complex 1 undergoes four distinct and reversible one-electron redox steps in dichloromethane at -186, -484, -1174, and -1524 mV versus a standard calomel electrode (ferrocenium+/ferrocene redox couple 409 mV). The two-electron reduction product of 1, [Bu4N]2[(PdS2C2(COOMe)2)6] (2), has been chemically isolated and characterized.

Raquel Terroba

Papers

[PdS2C2(COOMe)2](6n) (n = 0, -1, -2, -3, -4): hexanuclear homoleptic palladium dithiolene complexes.