Cationic rare earth metal alkyls as novel catalysts for olefin polymerization and copolymerization

New ionic half-metallocenes of early lanthanides

“…The field of polymerisation is particularly most concerned, with the elaboration of unique controlled structure specialty polymeric materials [3,4]. However, the potential of such compounds -also called half-sandwiches or half-metallocenes -in catalysis is still little explored compared to metallocenes, mainly because their synthesis remains a challenge [5], due to the occurrence of comproportionation reactions [6,7].…”

“…In the present paper, we propose an alternative method for the preparation of half-sandwiches of lanthanides in high yield, which conjugates the advantages of -bond metathesis, and the use of standard starting materials, the trisborohydrides Ln(BH 4 ) 3 (THF) 3 . Isolated complexes all exhibit the general ionic formula [(Cp R )Ln(BH 4 ) 3 ] 2 [Mg(THF) 6 ] (Cp R is a cyclopentadienyl ligand).…”

Rare earth metal bis(alkyl) complexes bearing a monodentate arylamido ancillary ligand: Synthesis, structure, and Olefin polymerization catalysis

“…Rare earth metal bisalkyl complexes bearing one anionic ancillary ligand have received much current interest because such complexes can be converted to the corresponding cationic monoalkyl species by treatment with an equimolar amount of a borate compound such as [Ph 3 C][B(C 6 F 5 ) 4 ] or [HNMe 2 Ph][B(C 6 F 5 ) 4 ], leading to formation of unique catalyst systems that differ from those derived from the conventional metallocene complexes [1][2][3][4]. To prevent possible ligand redistribution, most of the rare earth bisalkyl complexes reported so far were stabilized by multidentate ancillary ligands such as cyclopentadienyls [2], b-diketiminates [3g,5], benzamidinates [3d], triazacyclononane-amido [3h], deprotonated aza-crown [6], anilido-pyridine-imine [7], aminopyridinates [8], and amido-phosphine [9], while monodentate-ligand-supported rare earth metal bisalkyl complexes remained scarce [10].…”

“…Ligand redistribution was not observed in solution, as shown by the NMR spectra of 1, 2 and 4. 1 H NMR and 13 C NMR spectra of complexes 1, 2 and 4 in C 6 D 6 showed one set of signals for the NSiMe 3 , (1) 109.0(1) N(1)-Ln-O(1) 115.11 (7) 117.96 (7) 118.4 (1) 116.60(8) C(1)-Ln-C(5) 111.7 (1) 108 . CH 2 SiMe 3 , and thf units, and two sets of signals for the isopropyl groups on the phenyl ring, suggesting that rotation of the phenyl ring around the N-C9 bond is highly restricted, which is in consistence with their crystal structures. The methylene protons of the trimethylsilylmethyl groups in complexes 1 and 4 were observed as a singlet peak, while complex 2 showed a doublet (À0.21 ppm) due to Y-H coupling (J Y-H = 3.4 Hz).…”

Structural diversity in the borohydrido lanthanides series: First isolation and X-ray crystal structure of ionic

“…Since the last decade, an impressive number of reports have been devoted to polymerisation catalysis with lanthanide-based catalysts, and particularly in the fields concerning olefins [1,2], conjugated dienes and styrene [3]. Recently, we described the syntheses of (very) uncommon examples of early half-lanthanidocenes, Cp Ã0 LnðBH 4 Þ 2 ðTHFÞ n (Cp Ã0 ¼ C 5 Me n 4 Pr; Ln = Nd, n = 2; Ln = Sm, n = 1) and their use as precatalysts for trans-1,4-stereospecific polymerisation of isoprene in combination with dialkylmagnesium reagents [4,5].…”