Cationic alkyl rare-earth metal complexes

Zhang, L.X., Suzuki, T., Luo, Y. et al. (2007) Cationic alkyl rare-earth metal complexes bearing an ancillary bis(phosphinophenyl)amido ligand a catalytic system for living cis-1,4-polymerization and copolymerization of isoprene and butadiene. Angewandte Chemie International Edition, 46, 1909. 

Although heterobimetallic complexes with alkylated rare-earth metal centers were proposed to promote 1,3-diene polymerization via an allyl insertion mechanism, details of the polymerization mechanism and of the structure of the catalytically active center(s) are rare [58,83,118-125]. Moreover, until now, the interaction of the cationizing chloride-donating reagent with alkylated rare-earth metal centers is not well-understood. Lanthanide carboxylate complexes, which are used in the industrial-scale polymerization of butadiene and isoprene, are generally derived from octanoic, versatic, and... 

The yttrium silanolate complex 11 shows good catalytic activity with high anti-Markovnikov regioselectivity in the hydrosilylation of 1-decene (Tablet) [59]. Cationic silanolate rare-earth metal alkyl species derived from 11 were either inactive or exhibited significantly diminished activity, possibly as a result of tight binding of the benzene solvent as well as decomposition of the cationic metal hydride intermediate. 

A review article entitled "Bulky amido ligands in rare-earth chemistry Syntheses, structures, and catalysis" has been published by Roesky. Benzamidinate ligands are briefly mentioned in this contexD The use of bulky benzamidinate ligands in organolanthanide chemistry was also briefly mentioned in a review article by Okuda et al. devoted to "Cationic alkyl complexes of the rare-earth metals S mthesis, structure, and reactivity." Particularly mentioned in this article are reactions of neutral bis(alkyl) lanthanide benzamidinates with [NMe2HPh][BPh4] which result in the formation of thermally robust ion pairs (Scheme 55). ... 

A rare example of isospecific 3,4-polymerization of isoprene mediated by a constrained-geometry rare-earth metal initiator was reported by Z. Hou [270]. Binuclear silyl-linked cyclopentadienyl phosphido lanthanide dialkyl complexes were synthesized in good yields and activated with an equimolar amount of [Ph3C] [B(C6Fs)4] (Scheme 68). Cationic alkyl species were proposed as intermediates and an activation scenario was presented based on DFT calculations [270]. 

Figure 8.24 The structure of the dication [YMe(THF)6] + [78]. (Reproduced with permission from S. Arndt, etal., Homogeneous Ethylene-Polymerization Catalysts Based on Alkyl Cations of the Rare-Earth Metals Are Dicationic Mono(aUcyl)Complexe s the Active Species , Angewanrffe Chemie International Edition, 2003, 442, 5075-5079 (Eigure 2). Wiley-VCH Verlag GmbH Co. KGaA.)...

Arndt, S. and Okuda, J. (2005) Cationic alkyl complexes of the rare-earth metals synthesis, structure, and reactivity. Advanced Synthesis and Catalysis, 347, 339. 

Scheme 14 Synthesis of neutral and cationic rare-earth metal alkyl complexes bearing a bis(2-diphenylphosphinophenyl)amido (PNP )ligand...

A heterobimetallic Ga/cationic Yb/Schiff base complex as a Lewis acid/Lewis acid bifimctional catalyst catalyzes asymmetric a-addition of a-isocyanoacetamides to aryl, heteroaryl, alkenyl, and alkyl aldehydes (Scheme 6). The Schiff base derived from o-vanillin was suitable to utilize cationic rare earth metal triflates with good Lewis acidity in bimetallic Schiff base catalysis. 

Recently Hou reported the first example of efficient COG synthesis by rare earth metal catalysts. Cationic rare earth (group 3 and lanthanide) metal alkyls is an emerging new class of catalysts for the polymerization and copolymerization of various olefins including cyclic olefins. The combination of half-sandwich scandium bis (alkyl) complexes such as... 

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