Synthesis, Characterization, and Reactivity Studies of New Cyclam-Based Y(III) Complexes

[(Bn2Cyclam)Y(N(SiMe3)2)] was prepared by reaction of H2Bn2Cyclam with Y[N(SiMe3)2]3. The protonation of the macrocycle ligand in [(Bn2Cyclam)Y(N(SiMe3)2)] is observed upon reaction with [HNMe3][BPh4] leading to the formation of [(HBn2Cyclam)Y(N(SiMe3)2)][BPh4]. DFT analysis of [(Bn2Cyclam)Y(N(SiMe3)2)] showed that the HOMO is located on the anionic nitrogen atoms of the cyclam ring indicating that protonation follows orbital control. Addition of H2Bn2Cyclam and H2(3,5-tBu2Bn)2Cyclam to a 1:3 mixture of YCl3 and LiCH2SiMe3 in THF resulted in the formation of [((C6H4CH2)BnCyclam)Y(THF)(µ-Cl)Li(THF)2] and [Y{(η3-3,5-tBu2Bn)2Cyclam}Li(THF)], respectively. The reaction of H23,5-tBu2Bn2Cyclam with Y(CH2SiMe3)3(THF)2 was studied and monitored by a temperature variation NMR experiment revealing the formation of [(3,5-tBu2Bn2Cyclam)Y(CH2SiMe3)]. Preliminary catalytic assays have shown that [Y{(η3-3,5-tBu2Bn)2Cyclam}Li(THF)] is a very efficient catalyst for the intramolecular hydroamination of 2,2-diphenyl-pent-4-enylamine.

Jumping in the Chiral Pool: Asymmetric Hydroaminations with Early Metals

The application of early-metal-based catalysts featuring natural chiral pool motifs, such as amino acids, terpenes and alkaloids, in hydroamination reactions is discussed and compared to those beyond the chiral pool. In particular, alkaline (Li), alkaline earth (Mg, Ca), rare earth (Y, La, Nd, Sm, Lu), group IV (Ti, Zr, Hf) metal-, and tantalum-based catalytic systems are described, which in recent years improved considerably and have become more practical in their usability. Additional emphasis is directed towards their catalytic performance including yields and regio- as well as stereoselectivity in comparison with the group IV and V transition metals and more widely used rare earth metal-based catalysts.

Rare-earth metal-mediated PhCN insertion into N,N-bis(trimethylsilyl)naphthalene-1,8-diamido dianion – a synthetic approach to complexes coordinated by ansa-bridged amido-amidinato ligand

We report the first example of rare earth metal-mediated insertion of PhCN into Si–N bonds with the formation of an amidinato moiety.

Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes

A series of rare-earth metal diisopropylamide complexes has been obtained via salt metathesis employing LnCl3(THF)x and lithium (LDA) or sodium diisopropylamide (NDA) in n-hexane. Reactions with AM : Ln ratios ≥3 gave ate complexes (AM)Ln(NiPr2)4(THF)n (n = 1, 2; Ln = Sc, Y, La, Lu; AM = Li, Na) in good yields. For smaller rare-earth metal centres such as scandium and lutetium, a Li : Ln ratio = 2.5 accomplished ate-free tris(amido) complexes Ln(NiPr2)3(THF). The chloro-bridged dimeric derivatives [Ln(NiPr2)2(μ-Cl)(THF)]2 (Ln = Sc, Y, La, Lu) could be obtained in high yields for Li : Ln = 1.6-2. The product resulting from the Li : La = 1 : 1.6 reaction revealed a crystal structure containing two different molecules in the crystal lattice, [La(NiPr2)2(THF)(μ-Cl)]2·La(NiPr2)3(THF)2. Recrystallization of the chloro-bridged dimers led to the formation of the monomeric species Ln(NiPr2)2Cl(THF)2 (Ln = Sc, Lu) and La(NiPr2)3(THF)2. The reaction of YCl3 and LDA with Li : Y = 2 in the absence of THF gave a bimetallic ate complex LiY(NiPr2)4 with a chain-like structure. For scandium, the equimolar reactions with LDA or NDA yielded crystals of tetrametallic mono(amido) species, {[Sc(NiPr2)Cl2(THF)]2(LiCl)}2 and [Sc(NiPr2)Cl2(THF)]4, respectively. Depending on the Ln(iii) size, AM, and presence of a donor solvent, ate complexes (AM)Ln(NiPr2)4(THF)n show distinct dynamic behaviour as revealed by variable temperature NMR spectroscopy. The presence of weak LnCH(iPr) β-agostic interactions, as indicated by Ln-N-C angles <105°, is corroborated by DFT calculations and NBO analysis.

Recent developments in alkene hydro-functionalisation promoted by homogeneous catalysts based on earth abundant elements: formation of C-N, C-O and C-P bond

This Perspective article provides an overview of the recent advancements in the field of intra- and inter-molecular C-N, C-O and C-P bond formation by hydroamination, hydroalkoxylation, hydrophosphination, hydrophosphonylation or hydrophosphinylation of unactivated alkenes, including allenes, 1,3-dienes and strained alkenes, promoted by (chiral) homogeneous catalysts based on earth abundant elements of the s and p blocks, the first row transition metals and the rare-earth metals. The relevant literature from 2009 until late 2014 has been covered.

Rare-earth metal diisopropylamide-catalyzed intramolecular hydroamination

Well-defined rare-earth metal diisopropylamide complexes provide an exemplary case study to investigate the effect of donor solvent, alkali metal, chloro co-ligands, and in situ catalyst formation.

Metallacyclic yttrium alkyl and hydrido complexes: synthesis, structures and catalytic activity in intermolecular olefin hydrophosphination and hydroamination

Metallacyclic neutral and ionic yttrium alkyl complexes coordinated by a dianionic ene-diamido ligand ([2,6-iPr2C6H3NC(Me)=C(Me)NC6H3iPr2-2,6] = L(1)) [L(1)]Y(CH2SiMe3)(THF)2 (2), {[L(1)]Y(CH2SiMe3)2}(-){Li(THF)4}(+) (3), [L(1)]Y(OEt2)(μ-Me)2Li(TMEDA) (4) were synthesized using a salt-metathesis approach starting from the related chloro complex [L(1)]Y(THF)2(μ-Cl)2Li(THF)2 (1) in 70, 85 and 72% yields respectively. The reactions of 2 with H2 or PhSiH3 afford the dimeric hydride {[L(1)]Y(THF)(μ-H)}2(μ-THF) (5) containing two μ-bridging hydrido and one μ-bridging THF ligands (91 and 85% yields). The X-ray studies of complexes 2, 3 and 5 revealed η(2)-coordination of the C=C fragment of an ene-diamido ligand to a Y cation. DFT calculations were carried out to give an insight into the metal-ligand bonding and especially the interaction between the metal and the ene-diamido ligand. The observed bonding of the ene-diamido fragment is found to reflect the acidity of the metal center in the complex that is partially overcome by a better donation from the double bond (better overlap with an empty d orbital at the yttrium center). The treatment of complex 4 with DME resulted in the C-O bond cleavage of DME and afforded a three nuclear methoxide oxide complex [{[L(1)]Y}3(μ(2)-OMe)3(μ(3)-O)](2-)[Li(DME)3](+)2 (6). Complexes 2, 3, 5 and 7 proved to be efficient precatalysts for the intermolecular hydrophosphination of styrene, 4-vinylpyridine, and 1-nonene with PhPH2 and Ph2PH as well as hydroamination of styrene and pyrrolidine.