The gas phase structures of gold(I) complexes formed by intermolecular oxidation of selected terminal (phenylacetylene) and internal alkynes (2-butyne, 1-phenylpropyne, diphenylacetylene) were investigated using tandem mass spectrometry and ion spectroscopy in conjunction with quantum-chemical calculations. The experiments demonstrated that the primarily formed β-gold(I) vinyloxypyridinium complexes readily undergo rearrangement, dependent on their substituents, to either gold(I) α-oxo carbenenoids (a synthetic surrogate of the α-oxo carbenes) or pyridine adducts of gold(I) enone complexes in the condensed phase and that the existence of naked α-oxo carbenes is highly improbable. Isotopic labeling experiments performed with the reaction mixtures clearly linked the species that exist in solution to the ions transferred to the gas phase. The ions were then fully characterized by CID experiments and IRMPD spectroscopy. The conclusions based on the experimental observations perfectly correspond with the results from quantum-chemical calculations.

Attractive metallophilic (aurophilic, argentophilic, cuprophilic, etc.) interactions play an important role in arrangement and stabilization of oligonuclear metal ion complexes. We report a combined experimental and theoretical assessment of aurophilic interactions in closed-shell gold(I) dimers. The experimental binding energies were obtained for charged [(LH)AuCl]...[(L')AuCl] dimers (L is either a phosphine or an N-heterocyclic carbene ligand) in the gas phase. These energies served for benchmarking of correlated quantum chemical calculations (CCSD(T)-calibrated SCS-MP2/CBS method) that were then applied to neutral [(L)AuCl]...[(L')AuCl] dimers. The overall attractive interactions between monomeric units are in the order of 100-165 kJ mol in the charged dimers and of 70-105 kJ mol in the corresponding neutral dimers. In the neutral dimers, pure aurophilic interactions account for 25-30 kJ mol, the dipole-dipole interactions for 30-45 kJ mol, and the L···L' "inter-ligand" dispersion interactions for 5-25 kJ mol. Energy of the aurophilic interactions is thus comparable or even larger than that of strong hydrogen bonds.

The reaction of pentafluorophenyl 1′-(diphenylphosphino)­ferrocene-1-carboxylate (4) with ω-aminosulfonic acids H2N­(CH2) n SO3H (n = 1–3) in the presence of 4-(dimethylamino)­pyridine and triethylamine affords the respective phosphinoferrocene amidosulfonates as crystalline triethylammonium salts, viz., (Et3NH)­[Ph2PfcCONH­(CH2) n SO3] (1, n = 1; 2, n = 2; 3, n = 3; fc = ferrocene-1,1′-diyl), in good yields. These ligands react smoothly with [PdCl2(cod)] (cod = η2:η2-cycloocta-1,5-diene) to give the anionic square-planar bis-phosphine complexes trans-(Et3NH)2[PdCl2(Ph2PfcCONH­(CH2) n SO3-κP)2] (5, n = 1; 6, n = 2; and 7, n = 3). The chloride-bridged dimer [LNCPdCl]2, where LNC is 2-[(dimethylamino-κN)­methyl]­phenyl-κC 1 auxiliary ligand, is cleaved with 1 to give (Et3NH)­[LNCPd­(Ph2PfcCONHCH2SO3-κP)] (8), in which the amidosulfonate coordinates as a simple phosphine. A similar reaction of [LNCPd­(OAc)]2 and 1 proceeds under a partial elimination of (Et3NH)­OAc to afford a mixture of zwitterionic bis-chelate [LNCPd­(Ph2PfcCONHCH2SO3-κ2 O,P)] (9) and another Pd­(II) complex tentatively formulated as [LNCPd­(OAc)­(Ph2PfcCONHCH2SO3-κP)] (9a), from which the former complex separates as an analytically pure crystalline solid. All compounds have been characterized by spectroscopic methods and elemental analysis. The crystal structures of 1, 3, 5·2.5CH2Cl2, and 9·2CHCl3 were determined by single-crystal X-ray diffraction analysis. In addition, complexes 5–7 were tested as defined precatalysts for Pd-catalyzed cyanation of aryl bromides with K4[Fe­(CN)6]·3H2O in aqueous dioxane. Complex 5 proved the most active and generally applicable, affording the nitrile products in good to excellent yields.

1′-(Diphenylphosphino)-1-isocyanoferrocene (1) was prepared as a hybrid ligand for Ag(i) and Au(i) complexes; the catalytic activity of the Au(i) complexes was studied.

The gold(I) catalyzed reaction between phenylacetylene, pyridine N-oxide and acetonitrile leading, via a putative gold-α-oxocarbene intermediate, towards an oxazole product has been investigated. A novel mass spectrometric method called "delayed reactant labeling" is used to track consecutive and parallel reactions. It clearly shows that the intramolecular formation of a pyridine adduct of gold-α-oxocarbene is in competition with the formation of the oxazole product. The reaction mechanism most probably corresponds to competition between acetonitrile and pyridine in an almost barrierless reaction with putative gold-α-oxocarbene within the solvent cage. The detected ionic species have been characterized by helium tagging infrared photodissociation spectroscopy.

Dimeric Au(i) complexes with phosphinonitrile ligands remain highly catalytically active at low catalyst loadings thanks to self-stabilisation by dimerisation.

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Acylphosphines are an overlooked subclass of phosphine ligands with specific reactivity and ligating properties. This study describes the synthesis of the first ferrocene-based acylphosphine, FcC(O)PPh2 (1, Fc = ferrocenyl), the...