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

Abstract

Efforts to link phosphinimide and cyclopentadienyl ligands via metathesis were undertaken. To this end, the allylic phosphinimine t-Bu 2 (CH 2 dCHCH 2 C(Me 2 )PNSiMe 3 (1) and the Ti complexes 4) were prepared. Attempts to effect olefin metathesis on 4 using either [Cl 2 (PCy 3 ) 2 RudCHPh] or [Cl 2 (PCy 3 )(H 2 IMes)RudCHPh] as the catalyst were unsuccessful. Alternatively, the phosphinimine t-Bu 2 (CH 2 dCHCH 2 )PNSiMe 3 (5) was found to undergo olefin isomerization upon conversion to the phosphinimines t-Bu 2 (MeCHdCH)PNH ( 6) and t-Bu 2 (MeCHdCH)PNTi(NMe 2 ) 3 ( 7), t-Bu 2 (MeCHdCH)PNTiCl 3 (8), and t-Bu 2 (MeCHdCH)PNTiCl 3 (THF) (8 • THF). Direct reaction of 5 with TiCl 4 gave t-Bu 2 (CH 2 dCHCH 2 )PNTiCl 3 (9), which was readily converted to t-Bu 2 (CH 2 dCHCH 2 )PNTi-(C 5 H 4 C(Me)dCH 2 )Cl 2 (10). Repeated attempts to effect a ring closure by olefin metathesis resulted in no reaction. However, the species t-Bu 2 (CH 2 dCHCH 2 )PNTi(CpCH 2 CHdCH 2 )Cl 2 (11) was readily methylated to give t-Bu 2 (CH 2 dCHCH 2 )PNTi(CpCH 2 CHdCH 2 )Me 2 (12), and 11 in the presence of [Cl 2 (PCy 3 ) 2 RudCHPh] underwent olefin metathesis to give t-Bu 2 (CpCH 2 CHdCHCH 2 )PNTiCl 2 (13). Subsequent reaction with 9-BBN gave t-Bu 2 (CpCH 2 CH 2 CH(B(C 8 H 14 )CH 2 )PNTiCl 2 (14), while alkylation gave t-Bu 2 (CpCH 2 CHd CHCH 2 )PNTiMe 2 (15). In a similar fashion, the species t-Bu 2 (C 5 Me 4 CH 2 CHdCHCH 2 )PNTiCl 2 (20), t-Bu 2 (C 5 Me 4 CH 2 CHdCHCH 2 )PNTiMe 2 (21), t-Bu 2 (C 9 H 6 CH 2 CHdCHCH 2 )PNTiCl 2 (24), and t-Bu 2 (C 9 H 6 CH 2 CHdCHCH 2 )PNTiMe 2 ( 25) were prepared. A number of these compounds were screened for their ability to effect olefin polymerization using MAO, B(C 6 F 5 ) 3 , or [Ph 3 C][B(C 6 F 5 ) 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 • THF, 13, 15, and 20 are reported.

Synthesis and Characterization of Bidentate Rare-Earth Iminophosphorane o-Aryl Complexes and Their Behavior As Catalysts for the Polymerization of 1,3-Butadiene

“…Iminophosphoranes, though less investigated than imines, have shown good potential in coordination chemistry and more recently in catalysis. In particular the Cavell and Stephan groups used such ligands in olefin polymerization . For a few years our group has developed facile and straightforward synthetic methodologies to access different iminophosphorane-based ligand systems, which rely on the Kirsanov reaction involving bromination of a phosphine followed by reaction with a primary amine in the presence of a base.…”

High Spin Cobalt Complexes Supported by a Trigonal Tris(Phosphinimide) Ligand

“…We reasoned that terminal PN coordination to kinetically labile, late first row transition metals would be enforced via the incorporation of such ligands into a rigid, multidentate framework. To date, however, very few multidentate PN scaffolds have been prepared, and these suffer from pronounced flexibility and concomitant ambiguity in their metal coordination chemistry. − Hence, a tris-PN pro-ligand (H 3 R L) based on a rigid triarylbenzene backbone was designed (Scheme A). Using a similar backbone, tris-alkoxide, -siloxide, and -carboxylate variants have been described, − and tris-phosphine precursors (Int1) bearing phenyl- or adamantyl substituents are readily prepared (Supporting Information).…”

High Spin Cobalt Complexes Supported by a Trigonal Tris(Phosphinimide) Ligand

“…To date, however, very few multidentate PN scaffolds have been prepared, and these suffer from pronounced flexibility and concomitant ambiguity in their metal coordination chemistry. [22][23][24][25][26] Hence, a tris-PN pro-ligand (H3 R L) based on a rigid triarylbenzene backbone was designed (Scheme 1A). Using a similar backbone, tris-alkoxide, -siloxide, and -carboxylate variants have been described, [27][28][29] and tris-phosphine precursors (Int1) bearing phenyl-or adamantyl substituents are readily prepared (Supporting Information).…”