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RESEARCH PRODUCT

Nucleophilic attack within Ge, Sn and Pb complexes containing Me2N(CH2)(3) - as a potential intramolecular donor ligand

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Abstract Thirteen tin compounds LxPhySnClz and LPh2SnPhX (x=1–4, y=0–3, z=0–2, XPh, F, Cl, Br, I, OPh), six germanium compounds LxPhyGeClz and four lead compounds LPh2PbPhX (XPh, Cl, Br, I) containing the potential intramolecular donor LMe2N(CH2)3—have been synthesized by Grignard reactions, redistribution, halogenation, exchange of halide and phenylation. Evidence for 1,5-chelation in which the donor Me2N intramolecularly attacks the Lewis-acidic atoms Ge, Sn or Pb is provided by six crystal structure determinations: Me2N(CH2)3SnPh2Cl, 5; Me2N(CH2)3SnPh2Br, 5a; Me2N(CH2)3SnPh2I, 5b; Me2N(CH2)3SnPh2OPh, 5d; Me2N(CH2)3SnPh3·HCl·H2O. 1a; Me2N(CH2)3PbPh2I, 17b), and by solution 13C, 119Sn and 207Pb NMR data. This nucleophilic attack originates from the π-basicity and the charge flow from the ligands into a σ∗-LUMO at Ge, Sn or Pb. The electronegativity of the ligands at Ge, Sn or Pb inhibits nucleophilic attack. The ligand sequences PhCl2Ph2Cl>PhCl>Ph3 and Ph2IPh2BrPh2OPhPh2ClPh2F hold for an increasing approach N…Ge/Sn/Pb). The δ values (13C) of the α-methylene in CDCl3 solution are shifted distinctly to high frequency by increasing the approach between the Me2N donor and the central atom. A qualitative discussion of 119Sn NMR chemical shifts and spin-spin coupling constants is given, which supports the arguments on the basis of interactions of frontier orbitals.