ORGANOPLATINUM(II) AND ORGANOPLATINUM(IV) AND ORGANOPALLADIUM(II) AND ORGANOPLATINUM(IV) COMPLEXES OF A MACROCYCLIC THIOETHER - X-RAY CRYSTAL-STRUCTURE OF PT(C6H5)2(9S3), AN EXAMPLE OF EXODENTATE 1,4,7-TRITHIACYCLONONANE (9S3)

Displacement of coordinated 1,5-cyclooctadiene or norbornadiene from suitable precursors has given a series of eta1-C-bonded organoplatinum(II) complexes containing 1,4,7-trithiacyclononane (9S3), i.e. PtRR'(9S3) [R = R' = Me (1), Et (2), CH2CMe3 (3), CH2SiMe3 (4), Ph (5); R = Me, R' = CH2SiMe3 (6); R = Cl, R' = CH2SiMe3 (7)]. The dimethylpalladium(II) complex PdMe2(9S3) (8) has been obtained similarly from PdMe2(tetramethylethylenediamine), but Pd(CH2SiMe3)2(9S3)(9) could not be isolated in a pure state. Crystals of 5 are orthorhombic, space group Pbca, with a = 12.047(1) angstrom, b = 17.660(2) angstrom, c = 16.854(2) angstrom, and Z = 8. The structure was solved by heavy-atom methods and refined by least squares analysis to R = 0.031 and R(w) = 0.046 for 2498 unique observed reflections. The platinum atom is bound to two sulfur atoms of bidentate 9S3 and to two cis-phenyl groups in an almost planar array. The macrocyclic thioether adopts an exodentate conformation such that the uncoordinated sulfur atom points away from the metal atom, in contrast to the more usual endodentate conformation found in PdX2 (9S3) (X = Cl, Br). At room temperature, the 9S3 CH2 resonances in the H-1 and C-13{H-1} NMR spectra of 1-7 are broad; variable-temperature NMR studies of 2 and 4 suggest that this is caused by exchange of free and coordinated sulfur atoms. Complexes 3 and 4 react with halogens to give diorganoplatinum (IV)salts [PtXR2(9S3)]X [R = CH2SiMe3, X = I (10), Br (11); R = CH2CMe3, X = 1 (13)], and 1 and 2 oxidatively add methyl or ethyl iodide to give triorganoplatinum(IV) salts [PtR2R'(9S3)]I [R = R' = Me (14); R = Et, R' = Me (15); R = R' = Et (16)]; in these products 9S3 is probably tridentate. The palladium(II) complex 8 likewise adds methyl iodide to give [PdMe3(9S3)]I (17), which can be converted into a nitrate salt [PdMe3(9S3)]NO3 (18). These compounds show no tendency to reductively eliminate ethane, and they are the first isolable organopalladium(IV) complexes that do not contain a nitrogen donor, thus demonstrating the ability of endodentate 9S3 to stabilize octahedral or pseudooctahedral geometries.