Hp. Wang et al., Synthesis, structural characterization, and olefin polymerization behaviorof group 4 metal complexes with constrained-geometry carborane ligands, ORGANOMETAL, 20(24), 2001, pp. 5110-5118
Several new group 4 metal amide complexes with recently developed constrain
ed-geometry carborane ligands, [eta (5):sigma -Me(2)A(C9H6)(C2B10H10)]M(NR2
)(2) and [eta (5):sigma -Me(2)A(C5H4)(C2B(10)H(10))]M(NR2)(2) (A = C, Si; M
= Ti, Zr; R = Me, Et), were prepared in good yield via amino elimination r
eactions of M(NR2)4 and the corresponding neutral ligands in toluene. Treat
ment of the amide complexes with 2.5 equiv of (Me2NHHCl)-H-. or Me3N-HCl le
d to high yields of the corresponding chloride complexes, [eta (5):sigma -M
e(2)A(C9H6)(C2B10H10)}ZrCl(mu -Cl)(1.5)](2)(-) (A = C, Si), which could als
o be prepared from an equimolar reaction between ZrCl4(THF)(2) and [Me2C(C9
H6)(C2B10H10)]Li-2. In contrast, excess Me3SiCl could only convert [eta (5)
:sigma -Me2C(C5H4)(C2B10H10)]Ti(NMe2)(2) to [eta (5):sigma -Me2C(C5H4)(C2B1
0H10)]TiCl(NMe2), due to steric effects. All these new complexes have been
fully characterized by H-1, C-13, and B-11 NMR and IR spectroscopic data an
d elemental analyses. Thirteen out of fourteen newly prepared complexes hav
e been structurally characterized by single-crystal X-ray diffraction studi
es. The chloride complexes exhibit a very high ethylene polymerization acti
vity when they are activated with MMAO.