Jiří Schulz

Role of gold(I) α-oxo carbenes in the oxidation reactions of alkynes catalyzed by gold(I) complexes.

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.

The coordination behaviour of ferrocene-based pyridylphosphine ligands towards ZnII, CdII and HgII

The reaction of Group 12 metal dihalides MX(2) with the P,N-ligands [Fe(C(5)H(4)-PPh(2))(C(5)H(4)-2-py)] (1) (2-py = pyrid-2-yl), [Fe(C(5)H(4)-PPh(2))(C(5)H(4)-CH(2)-2-py)] (2) and [Fe(C(5)H(4)-PPh(2))(C(5)H(4)-3-py)] (3) (3-py = pyrid-3-yl) was investigated. For a 1 : 1 molar ratio of MX(2) and the respective ligand, three structure types were found in the solid state, viz. chelate, cyclic dimer and chain-like coordination polymer. The M(II) coordination environment is distorted pseudo-tetrahedral in each case. The P-M-N angle is much larger in the chelates (≥119°) than in the ligand-bridged structures (≤109°). 1 prefers the formation of chelates [MX(2)(1-κ(2)N,P)]. 3 forms coordination polymers [MX(2)(μ-3)](n). With the more flexible 2 all three structure types can occur. Dynamic coordination equilibria were observed in solution for the molecular complexes obtained with 1 and 2. NMR data indicate that the N- and P-donor sites interact most strongly with Zn(II) and Hg(II), respectively. While the formation of bis(phosphine)mercury complexes (soft-soft) was easily achieved, no bis(pyridine)zinc complex (borderline-borderline) could be obtained, which is surprising in view of the HSAB principle.

Synthesis, structural characterisation and bonding in an anionic hexavanadate bearing redox-active ferrocenyl groups at the periphery

Amide FcCONHC(CH2OH)3 (1; Fc = ferrocenyl), prepared from fluorocarbonylferrocene and tris(hydroxymethyl)methylamine, reacts with (Bu4N)3[H3V10O28] in N,N-dimethylacetamide to afford a salt containing a bis(triolato) capped hexavanadate anion bearing two ferrocenyl groups at its periphery, (Bu4N)2[{FcC(O)NHC(CH2O)3}2V6O13] (2). Compounds 1 and 2 were characterised by elemental analysis, spectroscopic methods (IR, NMR, and MS) and by cyclic voltammetry; the crystal structures of 1·1/2CH3CO2Et and (Bu4N)2[{FcC(O)NHC(CH2O)3}2V6O13]·2Me2NCHO were determined by X-ray diffraction analysis. Single-point DFT calculations performed for the isolated hexavanadate anion revealed the presence of 3-centre 4-electron (3c4e) O–V–O bonds on the hexavanadate cage, which are responsible for the high energy of the occupied frontier orbitals. The upper eleven occupied molecular orbitals including the HOMO are all delocalized over the hexavanadate cage and, therefore, any electrochemical oxidation can be expected to occur preferentially at the hexavanadate anion without affecting the pendant ferrocene moieties.

Tri-μ-chlorido-bis­[(η6-hexa­methyl­benzene)­ruthenium(II)] tetra­chlorido­ferrate(III)

The molecular geometry of the complex cation in the title structure, [(μ-Cl)3{RuII(η6-C6Me6)}2][FeIIICl4], compares very well with that reported earlier for the corresponding PF6 − salt [Pandey et al. (1999 ▶). J. Organomet. Chem. 592, 278–282]. The [FeCl4]− counter ion has a rather regular tetrahedral geometry with Fe—Cl distances and Cl—Fe—Cl angles in the range 2.1891 (7)–2.2018 (8) Å and 107.10 (3)–110.56 (3)°, respectively. There are no significant intermolecular interactions in the crystal except for some weak C—H⋯Cl contacts, which in turn indicates that the crystal packing is determined predominantly by electrostatic interactions between the ionic constituents.

1-Bromo-1′-(diphenyl­thio­phosphor­yl)­ferrocene

The title compound, [Fe(C5H4Br)(C17H14PS)], crystallizes with two practically undistiguishable molecules in the asymmetric unit, which are related by a non-space-group inversion. The ferrocene-1,1′-diyl units exhibit a regular geometry with negligible tilting and balanced Fe–ring centroid distances, and with the attached substituents assuming conformations close to ideal synclinal eclipsed.

Synthesis and Coordination Behavior of a Flexible Bis(phosphinoferrocene) Ligand

A symmetrical flexible bis(phosphinoferrocene) derivative, viz. bis[1′-(diphenylphosphino)ferrocenyl]methane (1), was prepared and studied as a ligand in Pd(II) and Au(I) complexes. The reactions of 1 with [PdCl2(cod)] (cod = cycloocta-1,5-diene) and [Pd(μ-Cl)(LNC)]2 (LNC = [2-(dimethylamino-κN)methyl]phenyl-κC1) produced bis(phosphine) complex trans-[PdCl2(1-κ2P,P′)] (4), wherein the ligand spans trans positions in the square-planar coordination sphere of Pd(II) and the tetranuclear, P,P-bridged complex [(μ(P,P′)-1){PdCl(LNC)}2] (5), respectively. In reactions with the Au(I) precursors [AuCl(tht)] and [Au(tht)2][SbF6] (tht = tetrahydrothiophene), ligand 1 gave rise to tetranuclear Au2Fe2 complex [(μ(P,P′)-1)(AuCl)2] (6) and to symmetrical macrocyclic tetramer [Au4(μ(P,P′)-1)4][SbF6]4 (7). All compounds were characterized by spectroscopic methods. In addition, the structures of compound 1, its synthetic precursor bis[1′-(diphenylphosphino)ferrocenyl]methanone (3), and all aforementioned Pd(II) and Au(I) complexes were determined by single-crystal X-ray diffraction analysis (some in solvated form).