Au-oxo complex

The purity of the terminal Au-oxo complexes, 3 and 4, was established by several methods including P NMR (3 and 4 have only one phosphorus peak at —8.55 and —13.15 ppm, respectively), cyclic voltammetry, electronic absorption spectroscopy, vibrational spectroscopy, detailed magnetic measurements and elemental analysis on all elements (triplicate analyses for Au) (44). The single peak in the PNMR spectra is consistent with the C2V symmetry of 3 and 4 established by multiple X-ray crystallographic structure determinations and a neutron diffraction study on 3 at liquid He... 

Fig. 6. Thermogravimetric analysis of the terminal Au-oxo complexes, 3 (black), 4 and their isostructural all-tungsten analogues (noted as P2W19 and P2W21, respectively).

Fig. 7. Structure of the singly-bridged Au-oxo complex, 3. Top left, combination polyhedral/ball-and-stick representation right, thermal ellipsoid plot. The PO4 and WOe polyhedra (or W atom) are shown in lighter and darker gray. Bottom left. X-ray structure of the coordination polyhedron...

The oxidation state of Au in both Au-oxo complexes 3 and 4 was thoroughly investigated by several chemical and physicochemical methods 44). First, bulk electrolysis (coulometry at controlled potential) confirms the Au(III) oxidation state assignment in both 3... 

The structures (geometrical and electronic) and physicochemical properties of the LTMO complexes are only now adequately established to facilitate interpretable reactivity studies. Parallel investigations are currently being conducted in both aqueous media using alkali metal salts of the complexes and in organic media (e.g., acetonitrile) using tetralkylammonium salts of the complexes. Thus far oxo transfer from the Pd-oxo and Au-oxo complexes to multiple organic substrates has been documented. This work will be reported subsequently. 

Although terminal oxo complexes of the late-transition-metal elements have been proposed as possible intermediates for oxidations catalyzed by these elements, late-transition-metal-oxo complexes were scarcely known. Hill and coworkers reported the synthesis and characterization of Pt4 + -, Pd4 + - and Au3 + -oxo complexes, [M(0)(0H2) W0(0H2) (PW9034)2]m (M = Pt, Pd and Au, n = 0-2), stabilized by electron-accepting polyoxotungstate ligands [109-111]. The stoichiometric reaction of the Au-oxo complex [Au(0)(0H2) W0(0H2) 2 (PW9034)2]9 with triphenylphosphine led to the formation of triphenylphosphine oxide. 

In neutron diffraction studies, the Fourier map does not show significant negative scattering density around the terminal Au-oxo oxygen 035, a result similar to the previous neutron diffraction on the terminal Pt-oxo complex 1, thus ruling out the possibility that a... 

Treatment of the cyclometallated complexes [Au(N,N,C)Cl][PF6] [N,N,CH = 6-methylbenzyl- (a) or 6-(l,l-dimethylbenzyl)-2,2 -bipyridine (b)] [20] with KOH or Ag20 in aqueous media affords the hydroxo complexes [Au(N,N,C)(OH)][PF6] (36) in fairly good yields [45b, 101] these are air-stable white solids, quite soluble in water and in many organic solvents. When refluxed in anhydrous THF they condense to give the oxo-bridged complexes [Au2(N,N,C)2( J--0)] (37) (Equation 2.10 in Scheme 2.5) which, in turn, can be obtained by a different route [102] (see Section 3.2) the reaction can be reversed by refluxing the 0x0 complex in water. 

Bond Distances (A) in the [M-Oel Cores of the Late Transition Metal-Oxo (LTMO) Complexes to Date (M = Pt, Pd and Au) from X-ray Diffraction Studies... 

Figure 1.70 Gold(lll) complexes with g-oxo ligands and environment of gold (111) in K7H2[Au(0)(OH2)P2W2o07o(OH2)2]-27H20.

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