title: Methylene-bridged, intramolecular donor-acceptor systems based on rare-earth metals and phosphinomethanides.
abstract: New geminally bonded intramolecular donor-acceptor systems, Cp2LnCH2PR2(Ln = Y, Ho, Er, R = CHMe2, CMe3), were prepared by salt elimination reactions between the dicyclopentadienyl-element chlorides (Cp2LnCl, Ln = Y, Ho, Er) and diorganylphosphinomethanides (R2PCH2Li; R = CHMe2, CMe3). These compounds, 1-6, were characterized by elemental analyses, mass spectrometry and X-ray diffraction experiments and the yttrium species additionally by NMR spectroscopy. In the solid state the molecular structures differ from each other, depending on the steric demand of the phosphorus substituents. For all iso-Pr-substituted compounds, dimers [Cp2LnCH2P(CHMe2)2]2with six-membered Ln-C-P-Ln-C-P rings in a chair-like conformation were observed. The sterically more demanding tert-butyl groups prevent dimerization but instead lead to species that undergo complexation of LiCl units by two monomers: [Cp2LnCH2P(CMe3)2·LiCl]. The solution NMR data for the yttrium compounds are consistent with the solid-state structures. Conversion with phenylacetylene afforded heteroleptic cyclobutane-like alkynyl-rare-earth metal complexes [Cp2Ln(μ-C[triple bond, length as m-dash]CPh)]2[Ln = Y (7), Ho (8), Er (9)]. Treatment of compounds 1-6 with 1,8-diethynylanthracene led to single metalation and dimerization and products with similar structural motifs as observed for complexes 7-9. Reactions with dihydrogen and carbon dioxide resulted in Y-C bond breaking, yielding Cp2YH/R2PCH3and CO2insertion products, respectively.
authors.affiliation: Fakultät für Chemie, Lehrstuhl für Anorganische Chemie und Strukturchemie (ACS), Centrum für molekulare Materialen CM2, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany. mitzel@uni-bielefeld.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Pieper
authors.forename: Jan-Hendrik
authors.initials: JH
authors.lastname: Lamm
authors.forename: Beate
authors.initials: B
authors.lastname: Neumann
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Stammler
authors.forename: Norbert W
authors.initials: NW
authors.lastname: Mitzel