Abstract
Abstract The synthesis and characterization of five new chiral dialkyltin complexes of N-salicylidene-L-valine, [2-O-3-R-5-R'C6H2C(H)=NCH(CH(CH3)2)C(O)O]SnR''2 (R, R', R'' = H, H, Me (1); H, Br, Me (2); OMe, H, Et (3); Br, Br, n-Bu (4); CH(OMe)2, Me, n-Bu (5)), have been reported. Compounds 1-5 are all (S)-enantiomers, and their crystal structures have been studied. Compound 1 displays a trimeric macrocyclic structure in which the coordination environment of each tin atom is a distorted [SnC2NO3] octahedron. In complexes 2-5, the tin atom has an intermediate geometry between trigonal bipyramidal and square pyramidal, and 3 is closer to a square pyramid. In crystals, a zigzag supramolecular chain is formed by the intermolecular C-H…O, O-H…O or Sn…O interactions.
Highlights
Compounds 1-5 are all (S)-enantiomers, and their crystal structures have been studied
Organotin compounds have been widely used in organic synthesis, catalysis, materials, and medicinal/biocidal aspects (Davies et al, 2008)
Organotin complexes with carboxylate ligands have attracted a lot of attention because they display higher catalytic and cytotoxic activity and the diversified structures (Arjmand et al, 2014; Bantia et al 2019; Davies et al, 2008; Eng, 2017; Tian et al, 2019)
Summary
The title complexes 1-5 were obtained from the reaction of dialkyltin dichloride, salicylaldehyde, L-valine and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) in 1:1:1:2 molar ratios with the yields of 69-87% (see Scheme 1). The Schiff base ligand, DBUsalt N-salicylidene-L-valinate, was formed in situ. The method of one-pot reaction is simpler and more effective than the two-step method that requires isolation of the Schiff base carboxylate ligand (Baul et al, 2005, 2017; Tian et al, 2005). These yellow chiral complexes are air stable and can be further explored as potential chiral Lewis acid catalysts.
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