Zirconium complexes of a cross-bridged cyclam

The acid-base reaction of tetrabenzylzirconium with 1,4,8,11-tetraazabicyclo[6.6.2]-hexadecane (H-2(CBC), 1) produces (CBC)Zr(CH2Ph)(2), 2. Similarly, reaction of 2 with phenols yields (CBC)Zr(CH2Ph)(O-2,6-C6H3Bu2t), 3, and (CBC)Zr(O-2,6-C6H3Me2)(2), 5. Prolonged heating of 3 leads to the metalated product (CBC)Zr[kappa(2)(C,O)-OC6H3(6-Bu-t)(2-CMe2CH2)], 4. Reaction of ZrCl2[N(SiMe3)(2)](2) with H-2(CBC) leads to (CBC)ZrCl2, 6, which subsequently affords (CBC)Zr(X)(Y) by salt metathesis (7, X = Cl, Y = N(SiMe3)2; 8, X = Y = CH3; 9, X = Y = CH2Si(CH3)(3)). Compounds 3 and 7 show restricted rotation about the Zr-O and Zr-N bonds, respectively, on the NMR time scale. For 3, the energy of activation for this process was determined to be 69 +/- 1 kJ/mol. Neither 6 nor 8 shows ethylene polymerization activity when treated with 500 equiv of MAO. Reaction of 6 with 2 equiv of n-BuLi in the presence of excess diphenylacetylene leads to the zirconacyclopentadiene 10, (CBC)Zr(C4Ph4). The structures of 5, 9, and 10 have been determined by X-ray crystallography, and all three display distorted octahedral geometry.