Use of Olefin Metathesis to Link Phosphinimide-Cyclopentadienyl Ligand Complexes: Synthesis, Structure, and Ethylene Polymerization Activity

Efforts to link phosphinimide and cyclopentadienyl ligands via metathesis were undertaken. To this end, the allylic phosphinimine t-Bu-2(CH2=CHCH2C(Me-2)PNSiMe3 (1) and the Ti complexes t-Bu-2(CH2=CHCH2C(Me-2)PNTi(Cp)Cl-2(2),t-Bu2CH2=CHCH2C(Me-2)PNTi(C5Me5)Cl-2 (3), and t-Bu-2(CH2=CHCH2C(Me-2)PNTi(C5H4CH2CH=CH2)Cl-2 (4) were prepared. Attempts to effect olefin metathesis on 4 using either [Cl-2(PCy3)(2)Ru=CHPh] or [Cl-2(PCy3)(H(2)IMes)Ru=CHPh] as the catalyst were unsuccessful. Alternatively, the phosphinimine t-Bu-2(CH2=CHCH2)PNSiMe3 (5) was found to undergo olefin isomerization upon conversion to the phosphinimines t-Bu-2(MeCH=CH)PNH (6) and t-Bu-2(MeCH=CH)PNTi(NMe2)(3) (7) t-Bu-2(MeCH=CH)PNTiCl3 (8), and t-Bu-2(MeCH=CH)PNTiCl3(THF) (8 center dot THF). Direct reaction of 5 with TiCl4 gave t-Bu-2(CH2=CHCH2)PNTiCl3 (9), which was readily converted to t-Bu-2(CH2=CHCH2)PNTi(C5H4 (Me)=CH2)Cl-2 (10). Repeated attempts to effect a ring closure by olefin metathesis resulted in no reaction. However, the species t-Bu-2(CH2=CHCH2)PNTi(CpCH2CH=CH2)Cl-2 (11) was readily methylated to give t-Bu-2(CH2=CHCH2)PNTi(CpCH2CH=CH2)Me-2 (12), and 11 in the presence of [Cl-2(PCy3)(2)Ru=CHPh] underwent olefin metathesis to give t-Bu-2(CpCH2CH=CHCH2)PNTiCl2 (13). Subsequent reaction with 9-BBN gave t-Bu-2(CpCH2CH2CH(B(C8H14)CH2)PNTiCl2 (14), while alkylation gave t-Bu-2(CpCH2CH=CHCH2)PNTiMe2 (15). In a similar fashion, the species t-Bu-2(C5Me4CH2CH=CHCH2)PNTiCl2 (20), t-Bu-2(C5Me4CH2CH=CHCH2)PNTiMe2 (21), t-Bu-2(C9H6CH2CH=CHCH2)PNTiCl2 (24), and t-Bu-2(C9H6CH2CH=CHCH2)PNTiMe2 (25) were prepared. A number of these compounds were screened for their ability to effect olefin polymerization using MAO, B(C6F5)(3), or [Ph3C][B(C6F5)(4)] as the activator. In general, active single-site catalysts were obtained, yielding high molecular weight polyethylene, although the activities were lower with MAO than with boron-based activators. Crystal structures of 3, 8 center dot THF, 13, 15, and 20 are reported.