Hydrido(acylenolato)cobalt(III)-Verbindungen mit Trimethylphosphan- Liganden: Insertionsreaktionen mit Alkinen und die ersten
Carbonylcobalt(III)-Komplexe
Hydrido(acylenolato)cobalt(III) Compounds Containing Trimethylphosphane Ligands:
Insertion Reactions with Alkynes and the First Carbonylcobalt(III) Complexes Hans-Friedrich Klein
a, Xiaoyan Li
a, Ulrich Fl¨orke
bund Hans-J¨urgen Haupt
baInstitut f¨ur Anorganische Chemie der Technischen Universit¨at Darmstadt, Petersenstraße 18, D-64287 Darmstadt
bAnorganische und Analytische Chemie der Universit¨at Paderborn, Warburger Straße 100, D-33095 Paderborn
Sonderdruckanforderungen an Prof. H.-F. Klein. Fax: +49 (0)6151-164173.
E-mail: hfklein@hrz2.hrz.tu-darmstadt.de
Herrn Prof. Dr. M. Schmidt zum 75. Geburtstag gewidmet
Z. Naturforsch.55 b,707–717 (2000); eingegangen am 27. April 2000 Hydridocobalt(III) Complexes, Insertion of Alkynes, Regioselectivity
Formal insertion of phenylethyne into Co-H functions of mer-octahedral acyl(enolato)- cobalt(III) hydrides 1 - 3 proceeds under ambient conditions affording 1-vinylcobalt(III) compounds where the dianionic acyl(enolato) ligands are derived from 2-formyl-4-phenyl- cyclohexanone (4), 1-formyl-cyclohexan-2-one (5), and 3-hydroxo-2,3-diphenyl-propenal (6).
Dissociation and association of trimethylphosphane results in a reversible transformation of penta-coordinate complexes4-6into hexa-coordinate ones7-9, respectively, involving dif- ferent tautomeric vinyl species. In toluene solution9rearranges by reductive C,C coupling into a 5,6-2-olefin(enolato)cobalt(I) complex10. Trimethylsilylethyne undergoes a hydrolytic desilylation reaction which is followed by reductive C,C-coupling reactions of acyl and vinyl functions selectively producing chelating1-enolato-5,6-2-olefin ligands in cobalt(I) com- pounds13-16where the (ax,eq)chelating ligands are derived from 1-formyl-cyclohexan-2-one (13), 3-hydroxo-2,3-diphenyl-propenal (14), 2-formyl--tetralone (15), and 2-formyl-4-tert- butyl-cyclohexanone (16). An axial position of the enolato-O donor in the trigonal bipyramidal configuration of complex 15 has been confirmed by X-ray diffraction analysis. With 1,4- bis(trimethylsilyl)buta-diyne 1,2-addition in cobalt(III) hydrides2, 3,11 (as deriverd from 2-formyl--tetralone), and12(as derived from 2-formyl-4-tert-butyl-cyclohexanone) produces 2-metalated vinyl groups in compounds17-20. Dissociation of trimethylphosphane from17 and19does not activate C,C coupling at the cobalt(III) centre of penta-coordinate21and22. Steric congestion in compounds17,18, and20favours exchange of trimethylphosphine for carbon monoxide affording the first octahedral carbonyl complexes of cobalt (d6) (23-25). In the crystal and in solution a meridional configuration is adopted by complex23with the CO group in a position opposite to the acyl function.
