2‐Acylpyrroles as Mono‐anionic O,N‐Chelating Ligands in Silicon Coordination Chemistry

Abstract

Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole (L(1)H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L(1)2SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L(1)2SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L(1)2SiCl2, L(1)2SiF2, L(1)2Si(OTf)2, L(1)2SiPhCl, and L(1)2SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L(1)3Si(+) and L(1) SiPh(+) were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L(1)2SiCl2 with a third equivalent of L(1)H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated C-C coupling of two ligands L(1).

Hexacoordinate Silicon Compounds with a Dianionic Tetradentate (N,N′,N′,N)-Chelating Ligand

“…Based on our experience with pyrrolide as anionic anchoring group in chelating ligands for Si coordination chemistry [20,64,[82][83][84], we studied the syntheses and molecular structures of silicon compounds with a pyrrole-2-carbaldimine functionalized (N,N 1 ,N 1 ,N)-chelating dianionic tetradentate ligand. This ligand, H 2 L, has already been reported in the literature [85] and was synthesized by condensation of o-phenylenediamine with two equivalents of pyrrole-2-carbaldehyde (Scheme 2).…”

Tp*Cu(i)–CN–SiL2–NC–Cu(i)Tp* – a hexacoordinate Si-complex as connector for redox active metals via π-conjugated ligands

“…13 Acetonitrile was purchased from Roth in an Ultra LC-MS grade quality (99.98%) and stored over activated molecular sieves 3 Å. Toluene was distilled from sodium and stored over sodium wire. Compound 1 (L 2 SiCl 2 ) was prepared as reported earlier.…”

“…31 Molecules were optimized at the DFT MPW1PW91/ 6-311G(d,p) level of theory. Chemical shifts are given in ppm relative to SiMe 4 (as internal standard for 1 H, 13 C and 29 Si) or BF 3 ·Et 2 O (externally referenced for 11 B). 1 H, 11 B, 13 C and 29 Si NMR spectra were recorded on a Bruker DPX 400 spectrometer or on a Bruker AVANCE 500 spectrometer.…”

“…13 Thus, we started introducing metal complexes into the Si coordination sphere of this type of complexes via Si−N coordination. 13 Thus, we started introducing metal complexes into the Si coordination sphere of this type of complexes via Si−N coordination.…”

Hydrosilylation of RN=CH Imino‐Substituted Pyridines without a Catalyst

“…For this reason, it is meaningful to omit the metalation step and to use mixtures containing silanes and neutral C=Y‐functionalized ligands (Y=O or NR). Recently, Wagler and Kroke used this concept and reported on the reactivity of 2‐acyl‐pyrroles with HSiCl 3 or H 2 SiCl 2 . They observed H 2 elimination as opposed to a reduction of the unsaturated C=O moiety.…”