Zwitterionic Trivalent (Alkyl)lanthanide Complexes in Ziegler-Type Butadiene Polymerization

Abstract

The organolanthanide complexes Ln{C(SiHMe 2) 3 } 3 (Ln = La, 1a; Ce, 1b; Pr, 1c; Nd, 1d) react with one or two equiv. of B(C 6 F 5) 3 to yield the well-defined zwitterionic species Ln{C(SiHMe 2) 3 } 2 HB(C 6 F 5) 3 (Ln = La, 2a; Ce, 2b; Pr, 2c; Nd, 2d) or LnC(SiHMe 2) 3 {HB(C 6 F 5) 3 } 2 (Ln = La, 3a; Ce, 3b; Pr, 3c; Nd, 3d), respectively. These complexes are shown to contain labile, bridging Si-H⇀Ln and oF ->Ln interactions based upon the observation of low one-bond silicon-hydrogen coupling constants (1 J SiH) in 1 H NMR spectra of 2a and 3a, the presence of one set of C 6 F 5 signals in the 19 F NMR spectra of 2a and 3a, the detection of only m-F and p-F resonances in 19 F NMR spectra of 2b-d and 3b-d, two ν SiH bands in IR spectra of 2a-d, and X-ray crystallography analyses of 2b and 3d. In addition, a hexametertoluene molecule is coordinated to neodymium in 3d. Reactions of 1a and (AlMe 3) 2 yield labile adducts with an approximate stoichiometry of 1a•3AlMe 3. Exchange between free and bound AlMe 3 groups was observed in EXSY NMR experiments with greater than 3 equiv. of AlMe 3. Compounds 2a-d and 3a-d, in the presence of AliBu 3 , are precatalysts for polymerization of butadiene. The neodymium alkyl 3d has the highest activity of the series, and its performance is consistent with chain transfer reactions with AliBu 3 .

Tris(benzhydryl) and Cationic Bis(benzhydryl) Ln(III) Complexes: Exceptional Thermostability and Catalytic Activity in Olefin Hydroarylation and Hydrobenzylation with Substituted Pyridines

“…Catalytic activity of cationic complexes bearing nucleophilic alkyl groups at an extremely Lewis acidic rare‐earth metal center [2a–c] in a variety of transformations of unsaturated substrates [2a–d,3a‐d,11d,e] as well as in C−H bond activation [2i,4] prompted permanent interest to this class of compounds. The synthesis of cationic species derived from 1 and 2 was attempted.…”

“…Molecular structures of 4 and 5 are depicted in Figure 3. The complexes adopt a structure of a contact ion pair [11d–e] . Two benzhydryl ligands are bound with Ln(III) centers in a fashion similar to that in 1 and 2 .…”

Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides

“…For example, zwitterionic Ce­{C­(SiHMe 2 ) 3 } 2 HB­(C 6 F 5 ) 3 and NdC­(SiHMe 2 ) 3 {HB­(C 6 F 5 ) 3 } 2 contain two Ln↼HSi per alkyl ligand as well as Ln←F and Ln↼HB in the coordination sphere . The Nd complex features hexahapto toluene coordination . These other ligands apparently do not interfere with the secondary interactions.…”

“…69 The Nd complex features hexahapto toluene coordination. 70 These other ligands apparently do not interfere with the secondary interactions. In contrast, the 1 J SiH of surface-supported yttrium silazido species Y{N(SiHMe 2 )tBu} n @MSN 700 , which also contains Ln↼HSi, suggested a siloxane-based oxygen donor in addition to the surface SiOY interaction.…”

Pentagonal Bipyramidal Ln(III) Complexes Containing an Axial Phosphine Oxide Ligand: Field-induced Single-ion Magnetism Behavior of the Dy(III) Analogues

“…There has been a significant renaissance in the chemistry of the rare-earth elements because of their photophysical properties and their applications in catalysis and in magnetic materials . In recent years lanthanide and some actinide complexes are finding increasing utility as molecular magnets (single-molecule and single-ion magnets (SMMs and SIMs, respectively)).…”