From Phosphidic to Phosphonium? Umpolung of the P -Bonding Situation in [CpFe(CO)(L)(η -P )] Cations (L=CO or PPh ).

Upon coordinating P to electron poor cyclopentadienyl-iron cations, the average P-P bond distances shrink and the respective P breathing mode in the Raman spectra (600 cm , P ) is blueshifted by >40 cm in [CpFe(CO)(L)(η -P )] cations (L=CO or PPh ). Analysis suggests that this corresponds to an umpolung of the bonding from more phosphidic in the known, electron-rich systems to more phosphonium-like in the reported electron-poor versions. This may open new functionalization pathways for white phosphorus P .

Investigations on silylium ions leading to a cyclobutenyl cation.

Instead of yielding the desired silylium ions, the reactions of different alkenes/alkynes with several [MeSi] sources mostly led to oligomerization, or - in the presence of MeSiH - hydrosilylation of the alkenes/alkynes. Yet, from the reaction of 2-butyne with MeSi-F-Al(OR) (R = C(CF)) the salt of the silylated tetramethyl cyclobutenyl cation [MeC-SiMe][--] ([--] = [(RO)Al-F-Al(OR)]) was obtained in good yield (NMR, scXRD, Raman, and IR). All the experimental and calculated evidence suggest a mechanism in which was formed a silylium ion as an intermediate.

Facile and systematic access to the least-coordinating WCA [(RO)Al-F-Al(OR)] and its more Lewis-basic brother [F-Al(OR)] (R = C(CF)).

By reaction of the Lewis acid MeSi-F-Al(OR) with a series of [PF] salts, gaseous PF and MeSi-F are liberated and salts of the anion [F-Al(OR)] ([f-al]; R = C(CF)) can be obtained. By addition of another equivalent of MeSi-F-Al(OR) to [f-al], gaseous MeSi-F is released and salts of the least coordinating anion [(RO)Al-F-Al(OR)] ([al-f-al]) are formed. Both procedures work for a series of synthetically useful cations including Ag, [NO], [PhC] and in very clean reactions with 5 g batch sizes giving excellent yields typically exceeding 90%.

Using the Lewis Acid Me Si-F-Al(OR ) To Prepare Phosphino-Phosphonium Cations with the Least-Coordinating Anion [(R O) Al-F-Al(OR ) ].

By reaction of two equivalents of Me Si-F-Al(OR ) 1 with an equimolar amount of PPh Cl, the salt [Ph P-PPh Cl] [(R O) Al-F-Al(OR ) ] 2 is prepared smoothly in 91 % yield (NMR, XRD). The synthesis of [Ph P-PPh ] [(R O) Al-F-Al(OR ) ] 3 is best achieved by a two-step reaction: first, two equivalents of 1 react with one PPh to give [Me Si-PPh ] [(R O) Al-F-Al(OR ) ] 4 (NMR, XRD), which, upon reaction with PPh Cl, yields pure 3 and Me SiCl (NMR, XRD). Typically, a stoichiometry of two equivalents of 1 with respect to one equivalent of the chloride donor should be used.

Homoleptic Gold Acetonitrile Complexes with Medium to Very Weakly Coordinating Counterions: Effect on Aurophilicity?

A series of gold acetonitrile complexes [Au(NCMe) ] [WCA] with weakly coordinating counterions (WCAs) was synthesized by the reaction of elemental gold and nitrosyl salts [NO] [WCA] in acetonitrile ([WCA] =[GaCl ] , [B(CF ) ] , [Al(OR ) ] ; R =C(CF ) ). In the crystal structures, the [Au(NCMe) ] units appeared as monomers, dimers, or chains. A clear correlation between the aurophilicity and the coordinating ability of counterions was observed, with more strongly coordinating WCAs leading to stronger aurophilic contacts (distances, C-N stretching frequencies of [Au(NCMe) ] units).

The Acidity of the HBr/AlBr3 System: Stabilization of Crystalline Protonated Arenes and Their Acidity in Bromoaluminate Ionic Liquids.

Bulk protonated mesitylene, toluene, and benzene bromoaluminate salts were stabilized and characterized in the superacidic system HBr/n AlBr3 with NMR spectroscopy and X-ray analysis of [HC6 H3 (CH3 )3 ](+) [AlBr4 ](-) (1), [HC6 H5 (CH3 )](+) [AlBr4 ](-) (2), and [C6 H7 ](+) [Al2 Br7 ](-) ⋅C6 H6 (3). Protonation attempts in bromoaluminate ILs led to a complete protonation of mesitylene, and a protonation degree of up to 15 % for toluene in the IL BMP(+) [Al2 Br7 ](-) . Benzene could only be protonated in the more acidic IL BMP(+) [Al3 Br10 ](-) , with a degree of 25 %.