It was found that homoleptic cyclopentadienyl lanthanide complexes CpLn (Ln = Y (1), Yb (2), Sm (3), Nd (4), La (5), Cp = cyclopentadienyl) can be employed as excellent catalysts for the hydroboration of various aldehydes and ketones toward pinacolborane. These robust lanthanide catalysts exhibited high reactivity with low catalyst loadings (0.01-1 mol %) under mild conditions and good functional group tolerability. These complexes also demonstrated uniquely carbonyl-selective hydroboration in the presence of alkenes and alkynes.

Simple and convenient n-BuLi is reported as a highly efficient catalyst in promoting the hydroboration of imines and alkynes.

Attempted synthesis of sterically demanding tris-beta-diketiminate complexes of europium led to oxidation-coupling of beta-diketiminates and the formation of the THF-solvated divalent europium complex Eu(L(2,6-Me(2)))(2)(THF) (L(2,6-Me(2)) = [{N(2,6-Me(2)C(6)H(3))C(Me)}(2)CH](-)), while the normal tris-beta-diketiminate complex Eu(L(2-Me))(3) for the less bulky ligand L(2-Me) ([{N(2-MeC(6)H(4))C(Me)}(2)CH](-)) was isolated by the same procedure.

Insertion of phenyl isocyanate into the Ln−N σ bond of (MeC5H4)2Ln(i-Pr)2(THF) (Ln = Y (1), Er (2), Yb (3)), which were synthesized by reactions of (MeC5H4)2LnCl(THF) with LiN(i-Pr)2, led to the isolation of {(MeC5H4)2Ln(THF)[O CN(i-Pr)2 NPh]} (Ln = Y (4), Er (5), Yb (6)). The latter is the active species for phenyl isocyanate polymerizations. The X-ray structure analysis of 4 shows that Y is coordinated to two methylcyclopentadienyl groups and one bidentate anion [O CN(i-Pr)2 NPh]- via a partial single bond, partial donor bond interaction with N1 and O1 atoms.

Highly efficient and selective hydroboration of aldehydes and ketones with HBpin is achieved by using the simple and convenient n-BuLi as a catalyst. The reaction proceeds rapidly with low catalyst loading (0.1-0.5 mol %) under mild conditions. Key features include the high catalytic efficiency, exceptional functional group compatibility, ample substrate scope, and high selectivity for aldehydes over ketones. Computational studies were carried out to provide a mechanistic insight into the n-BuLi catalyzed hydroboration of aldehydes/ketones with HBpin.

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Reaction of LnCl 3 (Ln = Y, Yb) with 2 equiv of NaL 2,6-ipr2 Ph (L 2,6-ipr2 Ph = [(2,6-i Pr 2 C 6 H 3 )NC(Me)CHC(Me)N-(C 6 H 5 )] − ) afforded the chlorides (L 2,6-ipr2 Ph ) 2 YCl (1) and (L 2,6-ipr2 Ph ) 2 YbCl (2). Crystal structure analysis revealed 2 to be the unsolvated monomer. Treatment of the chlorides 1 and 2 with NaBH 4 in a 1/1 molar ratio in THF led to the preparation of the monoborohydrides (L 2,6-ipr2 Ph ) 2 LnBH 4 (Ln = Y (3), Yb (4)) in good yields. Reaction of LnCl 3 (Ln = Y, Yb) with 2 equiv of NaL 2-Me (L 2-Me = [N(2-MeC 6 H 4 )C(Me)] 2 CH − ) in THF, followed by treatment with 1 equiv of NaBH 4 , afforded the monoborohydrides (L 2-Me ) 2 LnBH 4 (Ln = Y (5), Yb (6)). Complexes 3−6 were fully characterized, including X-ray crystal structure analyses. Complexes 3−6 are isostructural. The central metal in each complex is ligated by two β-diketiminate ligands and one η 3 -BH 4 − group in a distorted trigonal bipyramid. Complexes 3−6 were found to be highly active in the ring-opening polymerization of L-lactide (L-LA) and ε-caprolactone (ε-CL) to give polymers with relatively narrow molar mass distributions. The activity depends on both the central metal and the ligand (Y > Yb and L 2,6-ipr2Ph > L 2-Me ). The best control over the molar mass was found for complex 6. The M n (obsd) values (M n = the number-average molar mass) of the resulting PCL are in good agreement with M n (calcd), with a ratio of monomer to 6 of up to 1000. The polymerization kinetics of L-LA in THF at 20 °C by complex 6 displays a first-order dependence on the monomer concentration. Notably, the binary 6/ i PrOH system exhibited an "immortal" nature and proved able to quantitatively convert 10 000 equiv of L-LA with up to 200 equiv of i PrOH per metal initiator. All the obtained PLAs showed monomodal, narrow distributions (M w /M n = 1.06−1.11), with the M n values decreasing proportionally with an increasing amount of i PrOH. Complex 4 can also initiate the polymerization of methyl methacrylate (MMA) at −40 °C with high activity, affording the PMMA with 83.3% syndiotacticity.

Homoleptic lanthanide complexes coordinated by a Me-substituted Cp ligand [(MeCp)3Ln] demonstrate unprecedentedly high efficiency in catalyzing the hydroboration of aldehydes and ketones with pinacolborane. This protocol is also applicable for the hydroboration of aryl-substituted imines. In addition, broad functional group compatibility and excellent chemoselectivity is also achieved. DFT calculations are employed to shed light on the reaction mechanism.