Datensatz

Zusammenfassung

The (ethyne)nickel(0) complex (ⁱPr₂PC₂H₄PⁱPr₂)Ni(C₂H₂) (1) reacts with the stannene Sn[CH(SiMe₃)₂]₂ below - 30-degrees-C to yield the stanna(II)-nickela(II)-cyclobutene complex (ⁱPr₂PC₂H₄PⁱPr₂) activated NiCH = CHSn[CH(SiMe₃)₂]₂ (2; 83%) as the kinetically controlled product; 2 has been characterized by IR and NMR spectroscopy and an X-ray crystal-structure determination. The latter shows the central four-membered ring to be planar with a long Ni-Sn bond [2.626(1) angstrom]. According to the temperature-dependent. NMR spectra, 2 dissociates reversibly in solution to the starting components. The synthesis reaction thus represents an equilibrium as long as the temperature is below 20-degrees-C. These observations indicate that the structural lability of the stanna(II)-nickela(II)-cyclobutene moiety is associated with the weakness of the Ni-Sn bond. The bonding situation in 2 is best described as an "inner complex" in which a stannyl anion is coordinated to a nickel(II) cation. An ethereal solution of 2 undergoes an oxidative addition of one ethyne C-H bond to the stannene at 20-degrees-C to give the Ni(0)/Sn(IV) complex (ⁱPr₂PC₂H₄PⁱPr₂)Ni{η²-HC≡CSn(H)[CH(SiMe₃)₂]₂} (3) as the thermodynamically controlled product. Reaction of 3 with CO liberates the new alkyne ligand.