Reaction of the phosphinimines (Me)tBu2PNSiMe3 (1), (Me)tBu2PNC6H2Me3 (3), and (PhCH2)tBu2PNSiMe3 (6) with nBuLi and subsequently (C6F5)2BCl affords the four-membered heterocycles [((C6F5)2BCH2)tBu2PNSiMe3] (2), [((C6F5)2BCH2)tBu2PNC6H2Me3] (5), and [((C6F5)2BCH(Ph))t-Bu2PNSiMe3] (7), respectively. The related phosphinimine (iPr)tBu2PNSiMe3 (8) reacts with tBuLi to give (LiCMe2)tBu2PNSiMe3 (9), which reacts with (C6F5)2BCl to yield the five-membered heterocycle [((C6F5)2BCH2CH(Me))tBu2PNSiMe3] (10). Similarly, the species [(Me2AlCMe2)iPr2PNSiMe3] (12) and [((Me2N)2BCMe2)iPr2PNSiMe3] (13) were prepared from lithiation of the phosphinimine iPr3PNSiMe3 (11). In exploring the chemistry of these heterocycles, compound 2 reacts with [Me3NH]Cl and MeOH to open the heterocycle, giving [(C6F5)2B(Cl)CH2PtBu2NH(SiMe3)] (14) and ((C6F5)2B(OMe)CH2)tBu2PNH2 (15), respectively. Subsequent treatment of 15 with Me3SiCl affords the species ((C6F5)2B(Cl)CH2)tBu2PNH2 (16), while treatment of 16 with nBuLi gives [((C6F5)2BCH2)tBu2PNH)] (17). Compound 17 coordinates AlMe3 to give ((C6F5)2BCH2)tBu2PNH](AlMe3) (18), while 15 reacts with AlMe3 to give the six-membered heterocycle [((C6F5)2B(OMe)CH2)tBu2PNH)(AlMe2)] (19). This chemistry is discussed and the implications are considered. X-ray crystallographic data are reported for 2, 5, 7, 9, 10, 14, and 17.
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.
The tripodal phosphines MeC(CH(2)NMe)(3)P and N(CH(2)CH(2)NMe)(3)P were converted to the corresponding phosphinimines and the corresponding Ti-complexes MeC(CH(2)NMe)(3)PNTiCpCl(2) and N(CH(2)CH(2)NMe)(3)PNTiCpCl(2) were prepared. These species were also alkylated to give the corresponding dimethyl derivatives. Preliminary attempts to utilize these species in the polymerization of ethylene with MAO as the activator resulted in all but negligible activity. An alternative synthetic approach utilizing the bis-phosphinimine (CH(2)(Me)NPtBu(2))(2) was developed to prepare (CH(2)(Me)NP(tBu(2))NSiMe(3))(2), (CH(2)(Me)NP(tBu(2))NH)(2) and subsequently [(CH(2)(Me)NP(tBu(2))N)(2)]Ti(NMe(2))(2) , [(CH(2)(Me)NP(tBu(2))N)(2)]TiCl(2) and [(CH(2)(Me)NP(tBu(2))N)(2)]TiMe(2). For comparison purposes the related species [tBu(2)(Me(2)N)PN](2)TiCl(2) and [tBu(2)(Me(2)N)PN](2)TiMe(2) were also prepared. Compounds, using 2 equiv. of [Ph(3)C][B(C(6)F(5))(4)] as the activator, resulted in moderate to good polymerization activities.
A series of phosphinimide complexes of Hf are prepared and characterized. Reaction of the phosphinimine t-Bu3PNH with Hf(NEt2)4 gave (t-Bu3PN)Hf(NEt2)3 (1) but this species was not readily converted to the corresponding HfCl3-derivative. The reaction of 2 equiv. of t-Bu3PNH with Hf(NEt2)4, however, gave (t-Bu3PN)2Hf(NEt2)2 (2), which was readily converted to (t-Bu3PN)2HfCl2 (3) and (t-Bu3PN)2HfMe2 (4). Employing t-Bu3PNLi and HfCl4 afforded (t-Bu3PN)3HfCl (5) while reaction with CpHfCl3 gave rise to ligand redistribution reactions affording (t-Bu3PN)2HfCl2 and Cp2HfCl2. However, Cp(t-Bu3PN)2HfCl (7) was prepared by treating (t-Bu3PN)2HfCl2 with CpNa. The related species of Cp2(t-Bu3PN)HfCl (8) was synthesized by the reaction of Cp2HfCl2 and t-Bu3PNLi. Ligand redistribution was avoided in the reaction of Cp*HfCl3 as Cp*(t-Bu3PN)HfCl2 (9) and Cp*(i-Pr3PN)HfCl2 (10) were readily obtained and derivatized as Cp*(t-Bu3PN)Hf(NMe2)2 (11) and Cp*(t-Bu3PN)HfMe2 (12), respectively. Similarly, ((Me3Si)2C5H3)(t-Bu3PN)HfCl2 (13) was converted to ((Me3Si)2C5H3)(t-Bu3PN)HfMe2 (14). Reactions with Lewis acid activators were used to prepare Cp*(t-Bu3PN)HfMe(THF)MeB(C6F5)3 (15), (Cp*(t-Bu3PN)HfMe)(B(C6F5)4) (16), and (t-Bu3PN)2Hf(H2B(C6F5)2)2 (17). Preliminary testing of 3, 9, and 13 in ethylene polymerization is reported. Compounds 3, 4, 7, 9, and 17 are characterized crystallographically.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.