Lanthanide anilido complexes: synthesis, characterization, and use as highly efficient catalysts for hydrophosphonylation of aldehydes and unactivated ketones

• Published in: Dalton transactions : an international journal of inorganic chemistry 2014-06, Vol.43 (22), p.8355-8362
• Main Authors: Liu, Chengwei, Qian, Qinqin, Nie, Kun, Wang, Yaorong, Shen, Qi, Yuan, Dan, Yao, Yingming
• Format: Article
• Language: English
• Subjects: Aldehydes; Aldehydes - chemistry; Anilides - chemistry; Catalysis; Coordination Complexes - chemical synthesis; Coordination Complexes - chemistry; Ketones; Ketones - chemistry; Lanthanides; Lanthanum - chemistry; Ligands; Lithium; Molecular Structure; Nitrogen atoms; Nuclear magnetic resonance; Organophosphonates - chemistry; Rare earth metals
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt00522h

Lanthanide anilido complexes stabilized by the 2,6-diisopropylanilido ligand have been synthesized and characterized, and their catalytic activity for hydrophosphonylation reaction was explored. A reaction of anhydrous LnCl3 with 5 equivalents of LiNHPh-(I)Pr2-2,6 in THF generated the heterobimetallic lanthanide-lithium anilido complexes (2,6-(I)Pr2PhNH)5LnLi2(THF)2 [Ln = Sm(1), Nd(2), Y(3)] in good isolated yields. These complexes are well characterized by elemental analysis, IR, NMR (for complex ) and single-crystal structure determination. Complexes 1 - 3 are isostructural. In these complexes, the lanthanide metal ion is five-coordinated by five nitrogen atoms from five 2,6-diisopropylanilido ligands to form a distorted trigonal bipyramidal geometry. The lithium ion is coordinated by two nitrogen atoms from two 2,6-diisopropylanilido ligands, and one oxygen atom from a THF molecule. It was found that these simple lanthanide anilido complexes are highly efficient for catalyzing hydrophosphonylation reactions of various aldehydes and unactivated ketones to generate α-hydroxyphosphonates in good to excellent yields (up to 99%) within a short time (5 min for aldehydes, 20 min for ketones). Furthermore, the mechanism of hydrophosphonylation reactions has also been elucidated via(1)H NMR monitoring of reaction.