Metal–Metal Bonds between Group 12 Metals and Tin: Structural Characterization of the Complete Series of Sn-M-Sn (M=Zn, Cd, Hg) Heterodimetallic Complexes

Autor: Lutz, Matthias, Findeis, Bernd, Haukka, Matti, Graff, Roland, Pakkanen, Tapani A., Gade, Lutz H.
Zdroj: Chemistry - A European Journal; July 2002, Vol. 8 Issue: 14 p3269-3276, 8p
Abstrakt: Reaction of the lithium triamidostannate [MeSi{SiMe2N(p-Tol)}3SnLi(OEt2)] (1) with 0.5 molar equivalents of MCl2 (M=Zn, Cd, Hg) in toluene afforded the corresponding heterodimetallic complexes [MeSi{SiMe2N(p-Tol)}3Sn]2M {M=Hg (2), Cd (3), and Zn (4)}. The molecular structures of the mercury and cadmium complexes were determined by X-ray diffraction and found to adopt a linear Sn-M-Sn metal—metal bonded array (d(Sn&bond;Hg) 2.6495(2), d(Sn&bond;Cd) 2.6758(1) Å), these being the first Hg&bond;Sn and Cd&bond;Sn bonds to be characterized by X-ray diffraction. That the Hg&bond;Sn bonds are shorter than the Cd&bond;Sn bonds in the isomorphous complexes is attributed to relativistic effects in the mercury system. In contrast, the structure of the Zn analogue is unsymmetrical with one stannate unit being Sn&bond;Zn bonded (d(Sn(1)&bond;Zn) 2.5782(4) Å), while the ZnII atom bridges two amido functions of the second stannate cage, thus representing a second isomeric form of these complexes. The different degree of metal–metal bond polarity is reflected in the 119Sn NMR chemical shifts of the three complexes. Variable-temperature NMR studies and a series of 1H ROESY experiments of the cadmium complex 3 in solution revealed a dynamic exchange between the two isomers.
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