| Abstract
| - The respective reactions of [(C5H4)SiMe2(N-t-Bu)]MCl2 with [Mg(C4H6)(THF)2]n afford [(C5H4)SiMe2(N-t-Bu)]M(C4H6) (M = Ti, Zr). In the mononuclear Ti complex, the butadiene ligand adopts a symmetrical prone structure, whereas in the tetranuclear Zr complex, the butadiene ligands unsymmetrically bridge pairs of Zr atoms via a ((1,2,3-η3)−Zr-(4-μ2)-Zr) bonding interaction in the solid state.
- The metathetical reactions of [(C5H4)SiMe2(N-t-Bu)]MCl2, M = Ti, Zr, with [Mg(C4H6)(THF)2]n afford the respective group 4 metal butadiene complexes, [(C5H4)SiMe2(N-t-Bu)]M(C4H6). The solution NMR and X-ray crystallographic data for [(C5H4)SiMe2(N-t-Bu)]Ti(C4H6)indicate that the butadiene moiety adopts a symmetrical prone structure consistent with aTi(II) π-diene bonding representation. Alternatively, the solution and solid-state structuresfor its Zr analogue are markedly different. Whereas the observed chemical shift dispersionfor the anti and meso butadiene protons of [(C5H4)SiMe2(N-t-Bu)]Zr(C4H6) supports azirconacyclopentene structure in solution, the solid-state structure of this compound isactually tetranuclear. The four [(C5H4)SiMe2(N-t-Bu)]Zr units of {[(C5H4)SiMe2(N-t-Bu)]Zr(C4H6)}4 are related by a crystallographically imposed S4 rotation axis and are linked byfour unsymmetrically bridging butadiene groups via an unusual ((1,2,3-η3)-Zr−(4-μ2)-Zr)bonding interaction. The five-coordinate trigonal-bipyramidal geometry about the doublybridging carbon is characterized by a nearly linear Zr−(μ2-C)−Zr bond angle of 173.2(2)°and two rather long Zr−C bond distances of 2.636(5) and 2.530(5) Å.
|
