Macrocyclic Complexes of Palladium(II) with Benzothiacrown Ethers: Synthesis, Characterization, and Structure ofcisandtransIsomers

Abstract

A series of palladium(II) complexes with nitro- and formylbenzothiacrown-ether derivatives was synthesized. The spatial structure of the complexes was studied by NMR, X-ray diffraction analysis, and quantum chemical calculations (density functional theory). The cavity size and the ligand denticity were found to be crucial factors determining the geometric configuration of the thiacrown-ether complexes. Palladium(II) complexes with benzodithia-12(18)-crown-4(6) ethers were demonstrated to have a cis-configured S(2)PdY(2) fragment (Y = Cl, OAc). In the case of Pd(II) and benzodithia-21-crown-7 ethers, only complexes with a trans configuration of the S(2)PdY(2) fragment form. In the case of Pd(II) and nitrobenzomonothia-15-crown-5 ether, only 2(ligand):1(Pd) complex with trans configuration of the core fragment forms.

Aqueous Synthesis of 14‐15‐Membered Crown Ethers with Mixed O, N and S Heteroatoms: Experimental and Theoretical Binding Studies with Platinum‐Group Metals

“…Moreover, supporting NMR results (SI Figure S2) reveal the significant proton shifts of H β ( Δδ =0.04–0.12) and ArH β ( Δδ =0.39–0.61), which indicate coordination of S heteroatoms towards PdCl 2 (SI Table S4). Similar 1 H NMR shifts were also observed in literature for benzodithia‐12‐crown‐4 ether with PdCl 2 . New peaks were also observed for protons near the S heteroatoms due to conformational changes upon Pd 2+ complex.…”

“…Structure optimization of CE−M n+ complexes reveals that they form either of the two configurations: (1) M n+ is situated in the center of the CE or (2) outside the CE cavity. Similar planar configurations of the free and CE−M n+ complex have also been reported in literature ,. Hence, the free CE structure was optimized using the planar configuration, and the lowest energy CE conformation was selected and reported.…”

“…[12] On the other hand, remarkably higher distribution coefficients were observed for the Pd 2+ ‐selective CEs 2 d – 2 i (Log D Pd 2+ =0.97–2.38). CEs containing S 2 heteroatoms are shown to be efficient extractants for Pd 2+ in the presence of Pt 2+ ,,. Further extraction studies were done in the presence of other PGMs (Ru 3+ , Rh 3+ and Ir 3+ ) and metals (Sn 4+ , Te 4+ , Hf 4+ , and Au 3+ ) (Figure ).…”

“…[7,8] Moreover, CEs with mixed oxygen, nitrogen, and sulfur (O,N,S) heteroatoms are known to possess strong affinities towards PGMs. [9][10][11][12][13][14] Oxathia (O,S), oxaaza (O,N), and oxaazathia (O,N,S) CEs which contain soft heteroatoms showed specific coordination towards soft metals such as Pd 2 + or Pt 2 + according to the hard soft-acid base (HSAB) principle. [12,15,16] But despite their structural tunability for improved selectivity, syntheses of these CEs require multiple reaction steps using toxic and hazardous solvents and afford low overall reaction yields.…”

The effect of ring sizes and alkali metal cations on interaction energy, charge transfer and nonlinear optical properties of crown ether derivatives

“…15,16 Moreover, the structures of crown ethers have enormous varieties. 17 For example, the variation of ring sizes, 18 the oxygen atoms in the ring is replaced with nitrogen and sulfur heteroatoms, [19][20][21] the substituents of different functional groups in crown ether. 6 Due to the structural exibilities, thousands of crown compounds have been synthesized for specic goals.…”