Herein, rare-earth metal dialkyl complexes supported by a neutral pyrrolyl-functionalized β-diketiminato ligand with the formula LRE(CHSiMe)(thf) (RE = Y (1a), Dy (1b), Er (1c), Yb (1d); L = MeC(NDipp)CHC(Me)NCHCHNCH-2,5-Me, Dipp = 2,6-PrCH) were synthesized via the reactions of the β-diketimine HL with the rare-earth metal trialkyl complexes RE(CHSiMe)(thf) in high yields. The reactivities of 1 with pyridine derivatives, unsaturated substrates, and elemental sulfur were investigated, and some interesting chemical transformations were observed. Ligand exchange and activation of sp and sp C-H bonds occurred during the reactions with pyridine derivatives to afford different types of mononuclear rare-earth metal pyridyl complexes, namely, LEr(CHSiMe)(η-NCH) (2c), LRE(η-CH-2-NCH-4,6-Me) (RE = Y (3a), Er (3c)), and LRE(CHSiMe)(η-(C,N)-2-(2-CHNCH)) (RE = Er (4c), Yb = (4d)). Similarly, activation of the sp C-H bond occurred during the reaction of phenylacetylene with 1c to produce the dinuclear erbium alkynyl complex [LEr(CHSiMe)(μ-C[triple bond, length as m-dash]CPh)] (5c). The mixed amidinate-β-diketiminato ytterbium complex LYb[(Dipp)NC(CHSiMe)N(Dipp)](CHSiMe) (6d) was obtained by the insertion of bis(2,6-diisopropylphenyl)carbodiimide into a Yb-alkyl bond, as well as via the direct alkane elimination of a CHSiMe moiety with bis(2,6-diisopropylphenyl)formamidine to afford the erbium complex LEr(DippNCHNDipp)(CHSiMe) (7c). A rare sp C-H bond oxidation of the β-diketiminato backbone with elemental sulfur insertion was detected to provide the unprecedented dinuclear rare-earth metal thiolate complexes (LRE)(μ-SCHSiMe)(μ-SCC(Me)(NDipp)C(Me)NCHCHNCHMe-2,5) (RE = Y (8a), Er (8c)) in the reactions of S with 1a and 1c, respectively. The molecular structures of the complexes 1-8 were determined by single-crystal X-ray diffraction analyses.

Newly synthesized rare-earth metal alkyl complexes bearing a tripyrrolyl ligand act as excellent precatalysts for the cross-dehydrogenative coupling between various terminal alkynes and O/N-based monohydrosilanes of HSi(OEt) 3 /HSi(NMe 2 ) 3 , leading to the formation of a variety of alkoxysilylalkyne and aminosilylalkyne derivatives in good to high yields. The precatalystswere easily prepared in high yields via the reactions of RE(CH 2 SiMe 3 ) 3 (thf) 2 with the proligand H 2 L in a single step. Mechanistic studies reveal that treatment of 1 with phenylacetylene could generate the active catalytic species: dinuclear rare-earth metal alkynides (L(thf) n [RE(μ-CCPh)] 2 L) (RE = Y(5a), n = 1; Yb(5c), n = 0), which could react with HSi(OEt) 3 to produce the coupling product 4aa and the dinuclear rare-earth metal hydrides (L (thf)[RE(μ-H)] 2 L) (RE = Y(6a); Yb(6c)). By contrast, prior treatment of 1c with HSi(OEt) 3 proceeds via cleavage of the Si−O bond to produce the dinuclear ytterbium alkoxide (LYb(μ-OEt)) 2 7c, which is inert in the dehydrogenative coupling reaction. The results of the mechanistic studies are consistent with the observation that the reaction is greatly influenced by the addition sequence of precatalyst/alkynes/silanes.

Symmetrical and unsymmetrical N,N’‐disubstituted as well as trisubstituted ureas/thioureas by the hydroamination of isocyanates/isothiocyanates, and various phosphathioureas by the hydrophosphination of isothiocyanates have been synthesized in good to excellent yields under catalyst‐free and mild conditions. This protocol is also applicable for the efficient synthesis of chiral ureas and thioureas and common herbicides, such as fenuron and monuron.

Neutral rare-earth-metal monoalkyl complexes and anionic rare-earth-metal dialkyl complexes with a silicon-linked diarylamido ligand were synthesized and characterized, and their catalytic activities toward the additions of dialkyl phosphites to isocyanates were developed. Reactions of rare-earth-metal trialkyl complexes RE­(CH2SiMe3)3(THF)2 with a silicon-linked diarylamine ligand in n-hexane afforded the neutral rare-earth-metal monoalkyl complexes LRE­(CH2SiMe3)­(THF)2 (RE = Y (1), Er (2); L = (Me2Si)­(2,6- i Pr2C6H3N)2) in good yields. The dinuclear rare-earth-metal chlorides [LRE­(μ-Cl)­(THF)2]2 (RE = Y (3), Er (4)) were synthesized by the salt metathesis reaction of H2 L, n BuLi, and anhydrous RECl3. Treatment of the rare-earth-metal chlorides with 4 equiv of LiCH2SiMe3 in toluene generated the corresponding discrete heterobimetallic rare-earth-metal dialkyl complexes LRE­(CH2SiMe3)2(THF)­Li­(THF)4 (RE = Y (5), Er (6)). Further investigation showed that a wide variety of carbamoylphosphates were efficiently synthesized in high to excellent yields (up to 99%) via the additions of dialkyl phosphites to various alkyl- and aryl-substituted isocyanates in the presence of 0.1 mol % rare-earth-metal monoalkyl or dialkyl complexes as catalysts under solvent-free conditions at room temperature within 5 min, which provided a green and highly efficient method for the rapid construction of C–P bonds to afford various carbamoylphosphate derivatives.

A series of structurally well-defined cationic rareearth metal bridged sandwich pyrrolyl rare-earth metal dialkyl complexes with the general formula of (Me 3 SiCH 2 ) 2 RE(μ- Gd (2a), Dy (3a), Er (4a), Yb (5a), Lu (6a), thf = tetrahydrofuran) were synthesized by the reactions of rare-earth metal trialkyl complexes RE(CH 2 SiMe 3 ) 3 (thf) 2 with 1 equiv of 2-(2,6-diisopropylphenylaminomethyl)pyrrole (H 2 L) in toluene at room temperature. When the reaction temperature was raised to 45 °C, the centrosymmetric half-sandwich pyrrolyl rare-earth metal alkyl complexes (Me 3 SiCH 2 RELthf) 2 (RE = Y (1b), Gd (2b), Yb (5b)) were obtained in good yields, unexpectedly. Further studies revealed that the sandwich pyrrolyl rare-earth metal dialkyl complexes can be transferred to the half-sandwich rare-earth metal isomers by heating the C 6 D 6 solution to 60 °C. Single-crystal Xray diffraction analyses revealed that the sandwich pyrrolyl rare-earth metal dialkyls were bridged by an octahedral cationic rare-earth metal coordinated by two N atoms of the pyrrolyl rings, two N atoms of the amido moieties, and two O atoms of the thf molecules; while in their isomers, the rare-earth metals were surrounded by a pyrrolyl ligand, an alkyl group, a molecule of thf, and an η 5 type of pyrrolyl ring. All complexes were characterized by spectroscopic methods, elemental analyses, and single-crystal X-ray analyses. Moreover, the catalytic behaviors of these complexes were investigated, and the results showed that, in the presence of cocatalysts, the dinuclear rare-earth metal alkyl complexes exhibited high activities and high regio-and stereoselectivities for isoprene polymerization with cis-1,4-units up to 96.6%.