A series of new complexes, the blue compounds [PdCl(TeCH(2)CH(2)NMe(2))(PR(3))] (PR(3) = PEt(3), PPr(n)(3), PBu(n)(3), PMe(2)Ph, PMePh(2), PPh(3), PTol(3)) and the red [PtCl(TeCH(2)CH(2)NMe(2))(PR(3))] (PR(3) = PMe(2)Ph, PMePh(2)), were synthesized and studied spectroscopically ((1)H and (31)P NMR, UV/vis) and by cyclic voltammetry. The structures of [PdCl(TeCH(2)CH(2)NMe(2))(PPr(n)(3))] (2b) [PdCl(TeCH(2)CH(2)NMe(2))(PMePh(2))] (2e), [PtCl(TeCH(2)CH(2)NMe(2))(PMePh(2))] (2i), and the related [PtCl(SeCH(2)CH(2)NMe(2))(PEt(3))] (3) were determined crystallographically, revealing a typical pattern of trans-positioned neutral N and P donor atoms in an approximately square planar setting. The molecules 2b, 2e, and 2i were calculated by TD-DFT methodology to understand the origin of the weak (epsilon approximately 200 M(-1) cm(-1)) long-wavelength bands at about 600 nm for Pd/Te complexes such as 2b or 2e, at ca. 460 nm for Pt/Te systems such as 2i, and at about 405 nm for Pt/Se analogues such as 3. These transitions are identified as charge transfer transitions from the selenolato or tellurolato centers to unoccupied orbitals involving mainly the phosphine coligands for the Pt(II) compounds and more delocalized MOs for the Pd(II) analogues. Calculations and electrochemical data were used to rationalize the effects of metal and chalcogen variation.
The occurrence of cis or trans configurations in square planar diarylbis(dimethyl sulfoxide)platinum(II) complexes with S-bonded dmso ligands and aryl = 2,3,4,5,6-pentamethylphenyl,
2,4,6-trimethylphenyl, 2,6-dimethylphenyl, 2-, 3-, and 4-methylphenyl, and phenyl has been
investigated by multinuclear (1H, 13C, and 195Pt) NMR spectroscopy and crystal structure
analysis. Both methods confirm the cis configuration for complexes with the smaller phenyl
and methylphenyl (tolyl) ligands and the trans configuration for the compounds with the
bulkier ligands, starting from 2,6-dimethylphenyl. Spectroscopic criteria could thus be
established to identify configurational isomers. For the 2-tolyl complex an additional kind
of isomerism arises from the relative orientation of the two methyl substituents on the same
side (syn) or on different sides of the coordination plane (anti). 2D-NMR spectroscopy allowed
us to identify the conformers and to study isomerization mechanisms. DFT calculation results
agree well with the experimental structures and with the spectroscopic data.
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