Phosphinimide-phosphinimide ligands: New bulky ligands for ethylene polymerization catalysts

The phosphinimide-phosphines PPh2(NPR3) (R = i-Pr 1, t-Bu 2) were readily p repared; in 80-98% yield. These species react with AlMe3 or B(C6F5)(3) to f orm Me3AlPPh2(NPR3) (R = i-Pr 3, t-Bu 4) and (C6F5)(3)B(PPh2(NPi-Pr-3)) (5) , respectively. Oxidation of compounds 1 and 2 with Me3SiN3 yields Me3SiNPP h2(NPR3) (R = i-Pr 6, t-Bu 7). These species react with CpTiCl3 to give tit anium(IV) complexes CpTiCl2(NPPh2(NPR3) (R = i-Pr 8, t-Bu 9) and subsequent ly the alkylated complexes CpTiMe2(NPPh2(NPR3)) (R = i-Pr 10, t-Bu 11), Com pounds 8-11 were tested for activity in ethylene polymerization. In the pre sence of excess methylalumoxane, the species 8 and 9 gave rise to active si ngle-site catalysts, generating 299 and 34 gPE mmol(-1) h(-1), respectively . In contrast, activation of 10 and 11 by [Ph3C] [B(C6F5)(4)] showed neglig ible,polymerization activity. Reaction of 11 with B(C6F5)(3) was shown to g ive numerous products, one of which was the dicationic species [CpTi(mu -Cl )(NPPh2(NPt-Bu-3)](2) [BC6F5)(4)](2), 12. The formation of this species and the implications of these results for catalyst and ancillary ligand design are considered and discussed. X-ray crystallographic data are reported for 1, 3, 4, 8, and 12.