Silicon Tetrakis(trifluoromethanesulfonate): A Simple Neutral Silane Acting as a Soft and Hard Lewis Superacid.

A facile synthesis and isolation of pristine silicon tetrakis(trifluoromethanesulfonate), Si(OTf) , is reported, acting as the first neutral silicon-based Lewis superacid suitable towards soft and hard Lewis bases. Its OTf groups have a dual function: they are excellent leaving groups and modulate the degree of reactivity towards soft and hard Lewis bases. Exposed to soft Lewis donors, Si(OTf) leads to [L Si(OTf) ] complexes (L=isocyanide, thioether and carbonyl compounds) with retention of all Si-OTf bonds.

Isolable Silicon-Based Polycations with Lewis Superacidity.

Molecular silicon polycations of the types R Si and RSi (R=H, organic groups) are elusive Lewis superacids and currently unknown in the condensed phase. Here, we report the synthesis of a series of isolable terpyridine-stabilized R Si and RSi complexes, [R Si(terpy)] (R=Ph 1 ; R =C H 2 , (CH ) 3 ) and [RSi(terpy)] (R=Ph 4 , cyclohexyl 5 , m-xylyl 6 ), in form of their triflate salts. The stabilization of the latter is achieved through higher coordination and to the expense of reduced fluoride-ion affinities, but a significant level of Lewis superacidity is nonetheless retained as verified by theory and experiment.

Taming a silyldiium cation and its reactivity towards sodium phosphaethynolate.

A dicationic bis(NHC)-stabilised silyldiium complex, [bis(NHC)-SiPh] (7) (bis(NHC) = [CH(NCHNDipp)], Dipp = 2,6-PrCH), was synthesised for the first time. It reacts with sodium phosphaethynolate (NaOCP) as a source of monoanionic phosphorus to give the P-insertion product [bis(NHC)-PSiPh] (8). The latter comprises a seven-membered heterocycle containing a Si-P moiety which can easily be desilylated when exposed to dichlorophosphanes as exemplified by the synthesis of the diphosphanide cations [bis(NHC)-PPCy] (9) and [bis(NHC)-PPPh] (10).

(Oligo-)Thiophene Functionalized Tetraazaperopyrenes: Donor-Acceptor Dyes and Ambipolar Organic Semiconductors.

Tetraazaperopyrenes (TAPPs) have been functionalized with thiophene and terthiophene units of different architecture resulting in a variety of organic donor-acceptor (D-A) compounds. The influence of the connection of the thiophenes to the TAPP core on their structural, photophysical and electrochemical properties has been studied in detail by a combination of X-ray crystallography, UV-vis and fluorescence spectroscopy as well as cyclic voltammetry, which allowed the establishment of structure-property relationships. The HOMO-LUMO gap is significantly decreased upon substitution of the TAPP core with electron-donating thiophene units, the extent of which is strongly influenced by the orientation of the thiophene units.

Synthesis and oxidation of phosphine cations.

Cationic phosphines of the form [(L)PPh] are prepared by reaction of PhPCl with carbenes (L) including a chiral bis(oxazoline)-based carbene, a cyclic(alkyl)(amino) carbene (cAAC), and a 1,2,3-triazolium-derived carbene, affording the products, [(IBox-iPr)PPh][OSOCF] 1, [(cAAC)PPh][OSOCF] 2 and [((TripCHN(NMe)CPh)PPh)(AgCl)][Cl]3. Using PhPCl, the related dication [CH(NCHNDipp)PPh]4 was also prepared. Crystallographically-determined metric parameters and computational data indicate that these species are best described as cationic phosphines rather than phosphenium cations.