Thiolate-bridged Metal Complexes. Nickel(II), Palladium(II), and Cobalt(III) Binuclear Complexes of 1,5-Diamino-3-pentanethiol

A binucleating ligand with thiolate sulfur as a bridging atom, 1,5-diamino-3-pentanethiol (Hdpet) and its metal complexes, Ni2(dpet)2X2 (X=Br, ClO4, NO3, BPh4, and NCS) were synthesized. All the complexes are diamagnetic at room temperature. The Ni(II) and Pd(II) complexes assume binuclear thiolate-bridged square planar coordination. This structure is maintained even in aqueous solution. The electronic spectra of the Ni(II) complexes showed a band at 27.3×103 cm−1 corresponding to the 29.8×103 cm−1 band of [Ni2(dpl)2]2+ which is characteristic of oxo-bridged Cu(II) and Ni(II) complexes and was assigned to the pπ(O)→dσ(metal) transition. Several trials by different methods only resulted in the separation of a single species of Co(III) complex, Co2(dpet)3(ClO4)3. This was characterized as a bioctahedron facially joined at the three thiolate sulfur atoms.