Enantiopure Amidinate Complexes of the Rare-Earth Elements

Abstract

The synthesis of the new chiral amidine (S,S)-N,N′-bis(1-phenylethyl)pivalamidine ((S)-HPETA) and its corresponding lithium salt (S)-LiPETA are reported, and their solid-state structures were investigated by single-crystal X-ray diffraction. Depending on the stoichiometric ratio and the ion radius of the rare-earth metal, the reaction of (S)-LiPETA with anhydrous lanthanide trihalides (Ln = Sc, Y, La, Nd, Sm, Lu) afforded mono-, bis-, and tris(amidinate) complexes. The mono(amidinate) compound [{(S)-PETA}LaI 4 Li 2 (thf) 4 ], the bis(amidinate) complexes [({(S)-PETA} 2 Ln-μ-Cl) n ] (Ln = Sc, Y, Nd, Sm, Lu), and the tris(amidinate) compound [{(S)-PETA} 3 Y] were isolated and structurally characterized by single-crystal X-ray diffraction. For the bis(amidinate) compounds, either monomeric or chloro-bridged dimeric structures were observed in the solid state. Furthermore, chiral bis(amidinate)-amido and -alkyl complexes [{(S)-PETA} 2 Ln{E(SiMe 3 ) 2 }] (E = N, Ln = Y; E = CH, Ln = Sc, Y, Lu) were synthesized by salt metathesis and their catalytic activity and enantioselectivities were investigated in hydroamination/cyclization reactions. All of these compounds showed very good catalytic activity, and all of the investigated substrates were converted regiospecifically into their corresponding cyclic products under mild reaction conditions within good reaction times. The lutetium alkyl compound combined a high activity with good enantioselectivity.

Rigid NON-donor pincer ligand complexes of lutetium and lanthanum: synthesis and hydroamination catalysis

“…1; R ¼ R 0 ¼ t Bu) catalysts 9 showed comparable activity, while the lanthanum analogue was nearly inactive. [19][20][21][22][23][24][25][26][27][28][29] As noted above, we previously described the synthesis and hydroamination activity of [(XN 2 )Y(CH 2 SiMe 3 )(THF)] (XN 2 ¼ 4,5-bis(2,4,6-triisopropylanilido)-2,7-di-tert-butyl-9,9dimethylxanthene; d in Fig. 1), 10 and in this work we report the synthesis of lutetium and lanthanum XN 2 complexes.…”

Alkali Metal Complexes of a Bis(diphenylphosphino)methane Functionalized Amidinate Ligand: Synthesis and Luminescence

“…Hence, amidinates are widely used in the formation and stabilization of complexes, ranging from main group elements to transition and f‐block metals. [ 3 , 4 , 5 , 6 , 7 , 8 ] In general, monoanionic amidinates provide a mono‐ or bidentate support for metal ions, yet the introduction of additional heteroatom donor sites into the amidinate scaffold allows for extension to advanced coordination motifs as well as the potential formation of heteromultimetallic complexes. [9] In recent years, P,N‐type ligands, possessing both nitrogen and phosphorus donor sites, have been proven particularly suitable for this task (Figure 1 ).…”

“…This allows customization of the ligand in terms of steric demand and electronic properties as well as the introduction of additional functionalities. Hence, amidinates are widely used in the formation and stabilization of complexes, ranging from main group elements to transition and f‐block metals [3–8] . In general, monoanionic amidinates provide a mono‐ or bidentate support for metal ions, yet the introduction of additional heteroatom donor sites into the amidinate scaffold allows for extension to advanced coordination motifs as well as the potential formation of heteromultimetallic complexes [9] .…”

Computational Study of spx(x=1–3)‐Hybridized Be−Be Bonds Stabilized by Amidinate Ligands

“…Up to now, the reports on odd‐electron Be−Be bonds are rare compared with other metal elements and there are no reports about the Be−Be odd‐electron bond under neutral conditions or sp 3 hybridization. Through continuous literature retrieval and structure search, the bidentate amidinate (AMD) ligands came to our sight . They can simultaneously catch two Be atoms through two N sites (side‐on coordination mode shown in Scheme a) and the corresponding structures are then proved to be their global minima.…”