Four amidate-functionalized N-heterocyclic carbene (NHC) rare-earth metal amido complexes [(κ 2 -N,O-κ 1 -L) 2 REN(SiMe 3 ) 2 ] (L = 1-(C 6 H 5 CONCH 2 CH 2 )-3-(CH 3 ) 3 C 6 H 2 (N(CH) 2 NC)) [RE = Er (1), Y (2), Dy (3), Gd (4)] were synthesized by one-pot reactions of 2 equiv of (1-(C 6 H 5 CONHCH 2 CH 2 )-3-(CH 3 ) 3 C 6 H 2 -(N(CH) 2 NCH))Br (H 2 LBr) with 5 equiv of KN(SiMe 3 ) 3 followed by treatment with 1 equiv of RECl 3 in tetrahydrofuran at −40 °C. These complexes were fully characterized, and their catalytic activities toward hydroboration of unactivated imines and nitriles were investigated, and it was found that these complexes displayed excellent activities as well as remarkable functional group compatibility for imine and nitrile substrates such as halo-, alkyl-, hydroxyl-, N,N-dimethylamino-, and nitro-substituents. Among those, the chemoselectivity for this reaction among the common unsaturated functional groups was achieved in the order CO ≫ CN > CN > CO 2 Et > CC in the current catalytic system, which may facilitate their further application in synthetic chemistry.

A series of aluminum complexes with Schiff base bridged indolyl ligands were synthesized as rac-lactide polymerization catalysts.

The first series of lanthanide amido complexes incorporating a neutral pyrrole ligand in a constrained geometry architecture were synthesized, and their bonding, reactions, and catalytic activities were studied. Treatment of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 1 equiv of (N-C6H5NHCH2CH2)(2,5-Me2C4H2N) (1) afforded the first example of bisamido lanthanide complexes having the neutral pyrrole η5-bonded to the metal formulated as [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]Ln[N(SiMe3)2]2 (Ln = La (2) and Nd (3)). Reaction of [(Me3Si)2N]3Sm(μ-Cl)Li(THF)3 with 2 equiv of 1 produced the complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)][η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]]SmN(SiMe3)2 (4). Treatment of 3 with 2 equiv of 1 gave the sandwich neodymium complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]2Nd[η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)] (5), in which two neutral pyrroles bonded with metal in an η5 mode. Complex 5 could also be prepared by reaction of [(Me3Si)2N]3Nd(μ-Cl)Li(THF)3 with 3 equiv of 1. Reactivities of the lanthanide bisamido complexes were further investigated. Reaction of complex 2 with pyrrolyl-functionalized imine [2-(2,6- i Pr2C6H3NCH)C4H3NH] afforded a mixed η5-bonded neutral pyrrole and η1-bonded anionic pyrrolyl lanthanum complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]{η1-2-[(2,6- i Pr2C6H3)NCH]C4H3N}La[N(SiMe3)2] (6). Reactions of complexes 2 and 3 with pyrrolyl-functionalized secondary amine afforded the mixed η5-bonded neutral pyrrole and the η1-bonded anionic pyrrolyl lanthanide complexes [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)][(η1-2- t BuNCH)C4H3N]2Ln (Ln = La (7), Nd (8)) with dehydrogenation of the secondary amine. Investigation of the catalytic properties of complexes 2–8 indicated that all complexes exhibited a high activity with a high chemo- and regioselectivity on the addition of dialkyl phosphite to α,β-unsaturated carbonyl derivatives. An interesting result was found that 1,2-hydrophosphonylation substrates could be catalytically converted to 1,4-hydrophosphinylation products when the substrates are the substituted benzylideneacetones by controlling the reaction conditions.

Main observation and conclusion A novel indolyl‐based NCN pincer ligand precursor HL (HL = (1‐(2‐(CH2)4NCH2CH2)‐3‐(2,6‐iPr2C6H3N=CH)C8H5N)) was rationally and precisely designed, and successfully prepared in a high yield. Lithiation of HL with nBuLi in n‐hexane, followed by treatment with RECl3 in THF led to the isolation of rare‐earth metal chlorides in monomeric form (κ3‐L)RECl2(THF) (RE = Sc(2), Yb(3)), and dimeric form [(κ3‐L)RECl(THF)(μ‐Cl)]2 (RE = Er(4), Y(5)) bearing the novel indolyl‐based NCN pincer ligand in designed pincer ligation depending on different metal ionic radii; and the chloride bridged rare‐earth metal and lithium mixed complexes in form (κ2‐L)2RE(μ‐Cl)2Li(THF)2 (RE = Y(6), Dy(7). All complexes were fully characterized and their structures were determined. The diamagnetic complexes 2, 5 and 6 were furtherly characterized by the NMR spectroscopic method. The catalytic activity studies revealed that the central metal ions, borates, aluminum alkyls, and ligation of the central metal ions have influences on catalytic activity, and regio‐ and stereoselectivity for the polymerization of isoprene. With cooperation of the cocatalysts, the pincer‐type yttrium chloride 5 initiated the isoprene polymerization with a high activity producing polymers with high regio‐ and stereoselectivity (1,4‐cis polymers up to 99.6%), and the Mn as high as 8.76 × 105.

Three β-diketiminato proligands incorporating a thiophene or tetrahydrofuran heterocyclic group, H2 L1 , H2 L2 , and HL3 (MeC­(NDipp)­CHC­(Me)­N­(CH2)n-2-(HCG), HCG = C4H2S, n = 2, L1 ; n = 1, L2 ; HCG = C4H7O, n = 1, L3 ; Dipp = 2,6- i Pr2C6H3), have been developed. Unusual N,N,C tridentate β-diketiminato rare-earth metal monoalkyl complexes L1 RE­(CH2SiMe3)­(thf) (RE = Y (1a), Er (1b), Yb (1c), Lu (1d), thf = tetrahydrofuran) and L2 Yb­(CH2SiMe3)­(thf) (2c) were achieved unexpectedly by the reactions of RE­(CH2SiMe3)3(thf)2 with H2 L1 and H2 L2 , respectively. In this process, the C–H bond activation of the thiophene ring occurred. In sharp contrast, the treatment of RE­(CH2SiMe3)3(thf)2 with a tetrahydrofuran-functionalized β-diketiminato proligand HL3 , under the same conditions, gave five-coordinate N,N,O tridentate β-diketiminato rare-earth metal dialkyl complexes L3 RE­(CH2SiMe3)2 (RE = Y (3a), Er (3b), and Yb (3c)). In addition, their unique catalytic performances have been described. The monoalkyl complexes exhibited high efficiency toward the dimerization of various aldehydes, providing a wide range of carboxylic esters in good to high yields under mild conditions. The dialkyl complexes could promote the head-to-head dimerization of terminal alkynes to afford conjugated 1,4-disubstituted enynes with excellent regio- and stereoselectivity (up to 100% Z-selectivity). More importantly, a rare type of rare-earth metal complexes [{L 3RE­(μ-CCPh)}2(μ-η2:η2-PhCCCCPh)] (RE = Y (6a), Er (6b)) containing two bridging alkynyl groups and a Z-butatrienediyl fragment were isolated and characterized by the reaction of N,N,O tridentate rare-earth metal dialkyls with phenylacetylene, which is unarguably responsible for the outcome of Z-configured enynes during alkyne dimerization.