Rare‐Earth Metal Alkyl Complexes with 3‐Arylamido‐Functionalized Indolyl Ligands: Synthesis, Characterization and Reactivity^†

Abstract

of main observation and conclusion A series of dinuclear rare-earth metal alkyl complexes {[μ-η 2 :η 1 :η 1 -3-(LNCH)(CH2SiMe3)Ind]RE-(CH2SiMe3)(THF)}2 (L 1 = 2-t BuC6H4, RE = Y, Gd, Dy, Er, Yb; L 2 = 2,4,6-Me3C6H2, RE = Dy, Er; Ind = indolyl) and {[μ-η 2 :η 1 :η 1 -3-(LNCH2)Ind]RE(CH2SiMe3)(THF)}2 (L 1 , RE = Y, Dy, Er, Yb; L 2 , RE = Er, Yb) bearing 3-arylamido functionalized indolyl ligands having diverse bonding modes with metal ions were synthesized either by the insertion reaction of the imino group to the RE-C bond or by the alkane elimination reaction. In the preparation of above complexes, rare-earth metal alkyl complexes [μ-η 5 :η 1 :η 1 -3-(L 2 NCH)(CH2SiMe3)Ind]Gd(CH2SiMe3)(THF)}2 with a μ- 5 : 1 : 1 coordination mode to the gadolinium ion and {[μ-η 3 :η 1 :η 1 -3-(L 2 NCH2)Ind]Dy(CH2SiMe3)(THF)}2 with a μ- 3 : 1 : 1 coordination mode to the dysprosium ion were unexpectedly isolated. The reactions of 3-(L 2 N=CH)Ind with Er(CH2SiMe3)3(THF)2 at room temperature, generated a tetranuclear imino-indolyl erbium intermediate {[μ-η 1 :η 1 -3-(L 2 N=CH)Ind]Er-(CH2SiMe3)2(THF)}4, which can transform into the amido functionalized indolyl erbium complex in hot toluene. Moreover, the reactivities of the newly synthesized ytterbium complex with N-heterocyclic compounds were investigated, affording the corresponding products of the mixed pyridyl-indolyl, imidazolyl-indolyl, and ortho-metalated complexes. The yttrium complexes showed a high regioselectivity and steroselectivity for the isoprene polymerization with 1,4-trans selectivity up to 91.7% and 1,4-cis selectivity up to 96.1% in the presence of cocatalysts, respectively. Results and DiscussionReactions of 3-arylimino indoles with rare-earth metal alkyl complexes www.cjc.wiley-vch.de

Synthesis and Reactivity of the Rare-Earth Metal Complexes Bearing the Indol-2-yl-Based NCN Pincer Ligand

“…When complexes 1 were reacted with 2 equiv of phenylpyridine, producing the ortho –C-H bond of the phenyl ring activated complexes 7a – 7c (Scheme , Figure ). This reaction chemistry is similar to the chemistry reported previously c, but is different from the reactions between rare-earth metal alkyl complexes and 2-phenylpyridine, which produced the 2-pyridyl C–C coupling products . The reaction chemistry in the present case is also different from the reactions of the yttrium alkyl bearing the Y-CH 2 Ph bond complexes with 2-phenylpyridine to produce the C–H bond activation and 1,2- and 1,4-addition products (see Scheme S2, page S49), indicating ligand effects on the reactivity patterns.…”

“…Although the fundamental skeletons of pincer ligands are diverse, most of them are either fixed or nonfixed structures with central symmetry. In recent years, numerous reports have shown that nonsymmetric pincer ligands possess unique advantages compared with symmetric clamp ligands. ,, Therefore, the introduction of nonsymmetric functionality in pincer ligands for catalytic reactions and different molecule activations has become a great aspect of tunability. ,,− …”

“…The chemistry of indolyl-based rare-earth metal complexes has been gradually strengthened since Deacon reported the ytterbium(II) compounds containing the 2-phenylindolyl ligand in 1990 . As a result, various bonding modes like η 1 , μ – η 2 : η 1 , μ – η 3 : η 1 , μ – η 5 : η 1 , and μ – η 6 : η 1 of the indolyl with the rare-earth metals through the pyrrolyl and phenyl rings have been discovered. − However, rare-earth metal pincer complexes bearing an electron-rich heterocyclic indolyl skeleton have been less investigated.…”

Rare-Earth Metal Complexes Supported by 1,3-Functionalized Indolyl-Based Ligands for Efficient Hydrosilylation of Alkenes

“…The sharp singlet signals at δ = 0.17 ppm and δ = 8.58 ppm are assigned to the resonances of the CH 2 (SiCH 3 ) 2 groups and CHN, respectively. In the 13 C NMR spectrum of 7 , the 2-indolyl sp 2 carbanion were found to resonate at δ 211.36 ppm, which are similar to those in related indolyl-based rare-earth metal complexes. ,− …”

“…The bond length of Dy(1)–C(1) is longer than that found in the dinuclear complex {[μ-η 3 :η 1 :η 1 -3-(2,4,6-Me 3 C 6 H 2 NCH 2 )­C 8 H 4 N]­Dy­(CH 2 SiMe 3 )­(THF)} 2 [Dy–C sp 2 = 2.659(3) Å] after deduction of the influence of the coordination number, indicating the steric hindrance of the substituents on the indolyl ring . The C(14)–N(2) bond length (1.485(5) Å) in 6 was longer than that of CN double bond (1.29 Å), but is compared with the length of the typical C–N single bond (1.47 Å).The distance is similar to that found in complex {[μ-η 2 :η 1 :η 1 -3-(2- t BuC 6 H 4 NCH)­(CH 2 SiMe 3 )­C 8 H 5 N]­Dy­(CH 2 SiMe 3 )­(THF)} 2 (C–N = 1.489(9) Å), indicating that the imino group (−CHN) inserts into the Dy–CH 2 SiMe 3 bond to become an amido group [−(CH 2 SiMe 3 )­CH–N­( t BuC 6 H 4 )]. The Dy(1)–N(2) bond length 2.270(5) Å is slightly longer than that of 2.234(2) Å found in the complex {[μ-η 2 :η 1 :η 1 -3-(2- t BuC 6 H 4 NCH)­(CH 2 SiMe 3 )­C 8 H 5 N]­Y­(CH 2 SiMe 3 )­(THF)} 2 , which can be accounted for the steric and coordination number difference …”