Bis[2-(dimethylamino)ethyl] diselenide was prepared by the reaction of Na 2 Se 2 with ClCH 2 CH 2 NMe 2 . 2-(Dimethylamino)ethaneselenolate complexes of palladium() of the type [PdCl(SeCH 2 CH 2 NMe 2) 2 ] 4 have been synthesized and characterized by elemental analysis, IR and NMR ( 1 H, 31 P, 77 Se) spectroscopy. The structures of orange 1 and of violet (λ max = 514 nm) 2c have been established by single crystal X-ray diffraction analyses. The trimer 1 contains a six-membered Pd 3 Se 3 ring in twist conformation. The thermal behaviour of three complexes, yielding Pd 17 Se 15 has been investigated.

The reaction of py2Te2 or (3‐MeC5H3N)2Te2 with Na2PdCl4 in methanol yields an insoluble brown complex, [PdCl(TeNC5H3R)]n (R = H or Me). Several reactions of pyTe−, (3‐MeC5H3N)Te−, or (6‐MeC5H3N)Te− with various palladium(II) and platinum(II) complexes have been carried out. Complexes of the types [MCl(Te−N)(PR3)], [Pt(Te−N)2(dppe)], [Pt(Te−N)2(PPh3)2], and [Pt2(μ‐Te−N)2(dppe)2][BPh4]2 [M = Pd or Pt; Te−N = pyTe, (3‐ or 6‐MeC5H3N)Te] have been prepared and characterized by elemental analyses, UV/Vis, IR, and NMR (1H, 31P, 195Pt) spectroscopy. The complexes [MCl(Te−N)(PR3)] show irreversible oxidation and reduction by CV in DMF. The molecular structure of [PdCl{Te(3‐MeC5H3N)}(PPh3)] (2c) has been established by single‐crystal X‐ray diffraction analysis. The palladium atom is bound to the chelating 3‐methylpyridinetellurolate ligand, a chlorine atom and a PPh3 ligand. The pyrolysis of [PdCl{Te(3‐MeC5H3N)}(PR3)] (PR3 = PEt3 or PPh3) at 340 °C yields PdTe. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The self-assembly of Xantphos-capped M(OTf)2 (M = cis-[M′(Xantphos)]2+; M′ = Pd, Pt) with bridging ligands 1,4-benezenedithiol or 4,4′-biphenyldithiol has been investigated. The reactions have yielded complexes [M{S­(C6H4) n SH}]2(OTf)2 (I) and [M 2{S­(C6H4) n S}]2(OTf)4 (II) (n = 1 or 2). The equilibrium between I and II has been established in platinum complexes for n = 2, whereas the analogous Pd complex exclusively exist as II. These results are different from our previously reported dppe or triethyl phosphine-capped complexes which showed only type II. The same reaction with 1,3-benezenedithiol lead to the complex [M 2(SC6H4SSC6H4S)]­(OTf)2 (III), containing a S–S bond between two thiolate ligands, formed via a complex of type I in solution. Characterization of the complexes was accomplished by NMR spectroscopy, UV–vis spectroscopy and mass spectrometry, and X-ray crystallography. Density functional calculations were performed to estimate the relative stability of three types of complexes. The palladium complexes are excellent catalysts in Suzuki C–C cross coupling reactions under mild conditions, and can be reused eight times without losing significant yield. The activity of the Pd catalysts derived from three dithiol ligand follows opposite trend of the stability as III > II > I. The comparative catalytic activity of the tetranuclear Pd complexes (II) of bis-phosphines of varied bite angles, including the structurally characterized [Pd2(dppf)2(SC12H8S)]2(OTf)4 has also been demonstrated.

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