title: 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).
authors.affiliation: Institut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, 09596 Freiberg (Germany), Fax: (+49) 3731394058.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kämpfe
authors.forename: Erica
authors.initials: E
authors.lastname: Brendler
authors.forename: Edwin
authors.initials: E
authors.lastname: Kroke
authors.forename: Jörg
authors.initials: J
authors.lastname: Wagler
keywords: chelating ligands; coordination chemistry; hexacoordination; hypercoordination; isomerism; silicon