Reactivity of Zn(II), Mg(II) and Al(III) chlorides with a phosphinimine ligand: new tetrameric inverse crown ether structures.

Reaction of [Me3SiNPPh2CH3] 1 with ZnCl2 yields the dimer [ClZn(mu-Cl)(Me3SiNPPh2CH3)]2 2 whereas treatment of 1 with AlCl3 in THF leads to the monomeric N adduct [Cl3Al(Me3SiNPPh2CH3)] 3. Compounds 2 and 3 were found to be thermally stable and were fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analysis. On the other hand, treatment of phosphinimine 1 with (n)BuLi/ZnCl2 or (CH3)2CHMgCl yields the zinc and magnesium complexes [M4(Me3SiNPPh2CH2)4(mu4-O)(mu2-Cl)2] 5 (M = Zn) and 6 (M = Mg), respectively. These compounds can be considered as new examples of inverse crown ethers in which the oxygen atom is encapsulated by polar organometallic complexes in a tetrameric arrangement. In contrast, reaction of 1 with nBuLi/AlCl3 in Et2O under inert atmospheric conditions leads to the formation of the dimeric species [Cl2Al(Me3SiNPPh2CH2O)]2 7, which displays oxygen insertion into the C-Al bond, while the same reaction in the presence of air yields the compound [mu-(AlCl2)(NPPh2CH3)]2 8 with loss of ClSiMe3 and without oxygen insertion into the C-Al bond.