(Allyl)zirconium(IV) complexes with the N,N′-bis(trimthylsilyl)benzamidinato ( siam ) ligand - molecular structures and η1-η3 interconversions of the allyl groups

Article abstract of DOI:10.1002/cber.19961291113

Complexes of the type (siam)₂Zr(ailyl)₂ (1a) and (siarn)Zr(allyl)_nCl_m are described (2a: n = 1, m = 2; 2b: n = 2, m = 1; 2c: n= 3, m= 0; siam: N,N′-bis|triniethylsilyl)benzaniidinato group). The molecular structure of 1a shows that both allyl groups are differently bonded. One allyl ligand is η³-, the other η¹-coordinated. The X-ray crystal structure of the tris-(allyl) complex 2c shows a chiral molecule with two η³-allyl ligands. The third allyl ligand is coordinated in a mode inter-mediate between η³ and η¹ thus serving as a model for an intermediate in the η³-η¹ intramolecular rearrangement of the ally, ligands observed in solution. Temperature-dependent ¹H- and ¹³C-NiMR spectra of 1a, 2b and 2c indicate a rapid η³-η¹ rearrangement of the allyl groups at 60°C. At -50°C two different coordination modes of the ailyl groups can be observed in the case of 2b and 2c. VCH Verlagsgesellschaft mbH, 1996.