Synthesis and complexation studies of mesocyclic and macrocyclic polythioethers XIV. Crown thioether complexes of palladium(II) and platinum(II)

Abstract

This paper describes the synthesis and characterization of several crown thioether complexes of Pt(II) and Pd(II). We wish to report the syntheses and X-ray crystal structures of both the Pd(II) and Pt(II) complexes with the macrocyclic thioether complex, 1,4,7,11,14,17-hexathiacycloeicosane (20S6). Crystal data for [Pd(20S6)](PF 6) 2: C 14H 28F 12P 2PdS 6; monoclinic, space group P2 1 c ; a = 12.910(3) A ̊ , b = 9.810(20) A ̊ , c = 22.103(6) A ̊ , β = 102.170(20)°, V = 2700.39 A ̊ 3; Z = 4; R = 0.055; D = 1.931 g cm −3 ; 6346 reflections measured. Crystal data for [Pt(20S6)](PF 6) 2·CH 3NO 2: C 15H 31F 12NO 2P 2PtS 6; monoclinic, space group Cc; a = 12.321(5) A ̊ , b = 14.608(7) A ̊ , c = 17.032(5) A ̊ ; β = 98.15(3)°, V= 3034.55 A ̊ 3; Z= 4; R = 0.036; D = 2.045 g cm −3 ; 2777 reflections measured. Neither complex exhibits any significant electrochemistry or any visible absorption bands. Both complexes crystallize in the same linkage isomer where the metal ion is surrounded by a distorted square planar arrangement of four sulfur atoms. Two sulfur atoms that are adjacent to each other in the macrocyclic ring remain uncoordinated. 13C NMR spectroscopy reveals the presence of additional isomers in solution. We also wish to report the synthesis and X-ray crystal structure of the crown thioether complex, bis(1,4,7-trithiacyclodecane)platinum(II) hexafluorophosphate, [Pt(10S3) 2](PF 6) 2. The two 10S3 ligands are arranged around the platinum in pseudooctahedral fashion to yield the meso stereoisomer. Four of the six sulfur atoms from the 10S3 ligands form a square planar arrangement around the platinum (mean Pt-S equatorial bond distance = 2.30 Å). The remaining two sulfurs are coordinated axially at a much greater distance from the Pt (Pt-S axial = 3.21 Å). Crystal data for [Pt(10S3) 2](PF 6) 2·2CH 3NO 2: C 16H 34PdS 6P 2F 12N 2O 4; monoclinic, space group C2 c ; a = 22.473(9) A ̊ , b = 12.071(4) A ̊ , c = 11.186(3) A ̊ ; β = 94.14(3)°, V= 3026.53 A ̊ 3; Z = 4; R = 0.046; D = 1.991 g cm −3 ; 2836 reflections measured. Cyclic voltammetry measured in acetonitrile showed a single, reversible oxidation wave at +0.324 V versus F c F c + . Variable temperature 13C NMR spectroscopy shows no solvent-complex interactions, in contrast to the Pd(II) analog. The palladium(II) complex, [Pd(ttn) 2](PF 6) 2, which contains the acyclic thioether 2,5,8-trithianonane (ttn) was also prepared.