title: The first cyclopentadienylalkylphosphane nickel chelates: synthesis, structures, and reactions.
abstract: The first cyclopentadienylalkylphosphane nickel chelate complexes are reported. The anionic ligand obtained by reaction of spiro[2.4]hepta-4,6-diene with lithium di-tert-butylphosphide was treated with NiCl2 to yield [eta(5):kappa(1)-(di-tert-butylphosphanylethyl)cyclopentadienyl]chloronickel(II). From this complex, some acetonitrile-stabilized cationic complexes were obtained by reaction with the respective silver salts in acetonitrile. Methyl- and alkynylnickel chelates were prepared by reaction of the chloronickel complex with methyllithium and by copper-mediated coupling with terminal alkynes, respectively. Some of the complexes prepared were investigated by X-ray crystallography or cyclic voltammetry. The alkynylnickel chelates undergo cycloaddition reactions with ethoxycarbonylisothiocyanate or tetracyanoethylene, and the cyclobutenes obtained undergo ring opening to the corresponding dienes. The study includes an NMR spectroscopic investigation of the two conformers of one of these dienes.
authors.affiliation: Institut für Organische Chemie, Leibniz Universität Hannover, Schneiderberg 1B, D-30167 Hannover, Germany.
authors.forename: Mazhar
authors.initials: M
authors.lastname: Hussain
authors.forename: Dieter
authors.initials: D
authors.lastname: Albert
authors.forename: Rudolf
authors.initials: R
authors.lastname: Wartchow
authors.forename: Holger
authors.initials: H
authors.lastname: Butenschön