Lanthanide Carboxylate Precursors for Diene Polymerization Catalysis:  Syntheses, Structures, and Reactivity with Et₂AlCl

Abstract

Synthetic, structural, and reactivity results are presented on neodymium and lanthanum carboxylates that can function as models for diene polymerization catalysts. The neodymium and lanthanum carboxylates {Nd[O 2 CC(CH 3 ) 2 CH 2 CH 3 ] 3 } x (1) and {La[O 2 CC(CH 3 ) 2 CH 2 CH 3 ] 3 } x (2) were synthesized from the lanthanide metal and 2,2-dimethylbutyric acid in the presence of a catalytic amount of HgCl 2 and Hg(OAc) 2 . Nd 2 [O 2 CCH(C 6 H 5 )CH 2 CH 3 ] 6 [HO 2 CCH-(C 6 H 5 )CH 2 CH 3 ] 4 (3) was prepared similarly from neodymium powder and 2-phenylbutyric acid. 1 and 2 crystallize from hot pyridine as the dimeric pyridine adducts Nd 2 [O 2 CC(CH 3 ) 2 -CH 2 CH 3 ] 6 [pyridine] 4 (4) and La 2 [O 2 CC(CH 3 ) 2 CH 2 CH 3 ] 6 [pyridine] 4 (5). 3 crystallizes from hexanes as the carboxylic acid adduct. 1 and 2 react with Et 2 AlCl to form the isolable solids 6 and 7, which react with Al( i Bu) 3 to generate catalytically active systems which polymerize isoprene, ethylene, and styrene. Although crystallization of 6 from THF forms NdCl 3 (THF) 4 (8) and crystallization of 7 from pyridine forms [LaCl 3 (pyridine) 4 ] 2 (9), complexes 6 and 7 are not simply LnCl 3 , since elemental analyses show that they contain aluminum.

Novel Methylaluminoxane‐Activated Neodymium Isopropoxide Catalysts for 1,3‐Butadiene Polymerization and 1,3‐Butadiene/Isoprene Copolymerization

“…Similar results were observed with alkylaluminum‐based Nd catalysts . This effect of chlorine components might be due to the formation of Nd‐Cl cis ‐1,4 regulating species …”

50 Jahre “Chemie in unserer Zeit”

“…Within the strands, the La–N distances range from 268.2(2) to 274.2(2) pm. This is in the region of expected La III –N distances found for example in [LaCl 3 (pyridine) 4 ] 2 10. The corresponding Ce–N distances range from 265.4(2) to 272.0(2) pm, which is also in the region of expected Ce III –N distances in [CeCl 2 (μ‐Cl){py‐( R , R )‐chxn}] 2 [py‐( R , R )‐chxn = N, N ′‐bis(2‐pyridyl‐methylidene)‐1, 2‐( R , R )‐cyclohexanediamine) 11.…”

“…These interatomic distances are all in good accordance with distances in the compounds [LaCl 3 (pyridine) 4 ] 2 (La–Cl term . 277.78–278.59 pm)10 and [La(μ‐Cl) 3 (thf) 2 ] n (La–Cl bridg . 287.3–296.8 pm) 15.…”

Local structure analysis around the Nd center in a ternary catalyst comprising Nd(vers)3, Al(iBu)3 and Al(iBu)2Cl by XAFS

“…This result shows that Cl atoms from Al( i Bu) 2 Cl must contribute to the near neighbors. A previous study 26 of the reaction of lanthanide carboxylates with ethylaluminum chloride also claimed that such a reaction did not simply make the metal trichlorides. After testing various bonding combinations to the Nd center, a three-subshell model (Nd-C, Nd-Cl, and Nd-Al) can fit the EXAFS oscillations very well and give reasonable fitting parameters.…”