Chemistry of group(IV) phosphinimide complexes.
Abstract
Complexes of zirconium and titanium using phosphinimine as the ligand system were prepared. Some of these complexes were tested for activity in ethylene polymerization. Complexes of the form Cp*Zr(NPR3)Cl2 where R = i-Pr 41, t-Bu 53 were readily prepared. A series of the corresponding dialkyl derivatives Cp*Zr(NPR 3)R'2 where R = i-Pr, R' = Me 42, eta3-allyl 43, Ph 45, Cp 47 and R = t-Bu, R' = Me 5470, eta 3-allyl 44, Ph 46, Cp 48 were also generated. Complexes 41, 44, 46, 47, 49, 50 and 5470 were characterized crystallographically. Catalysts derived from complexes 41 and 53 gave minimal activities while complexes 42 and 54 gave no activity in ethylene polymerization. In the presence of [Ph3C][B(C6F5)4], complex 49 Cp*Zr(NPi-Pr3)( s-cis-eta4-2,3-dimethyl-1,3-butadiene) achieved higher activity while the tri-t-butyl analogue 50 achieved no activity in ethylene polymerization. Further GPC studies of the generated polyethylene suggest degradation occurred and the formation of more than one active species under the employed polymerization conditions. A new class of ancillary ligands, phosphine-phosphinimine R3 PNPPh2 where R = i-Pr 58, t-Bu 59 were developed. Compounds of the form R 3PNPPh2R' where R = i-Pr, R' = TMA 60, B(C6F5)3 62, NTMS 63 and R = t-Bu, R' = TMA 61, NTMS 64 were generated. The corresponding titanium dichloride complexes CpTi(NPPh2(NPR3))Cl 2 where R = i-Pr 65, t-Bu 66 and dimethyl analogues CpTi(NPPh2(NPR3))Me 2 where R = i-Pr 67, t-Bu 68 were subsequently prepared. Complexes 58, 60 , 62 and 65 were characterized crystallographically. Catalysts derived from complexes 65 and 66 achieved high activity, while those from 67 and 68 showed no activity in ethylene polymerization. This is presumably due to steric congestion. Complexes 65 and 66 are in fact promising new homogeneous "single site" catalyst precursors. Source: Masters Abstracts International, Volume: 44-01, page: 0356. Thesis (M.Sc.)--University of Windsor (Canada), 2000.