MONOMERIC SELENOPALLADATES AND SELENOPLATINATES

The compounds [NEt4]5[2Pd(Se4)2.1/2Pd(Se5)2], alpha-[PPh4]2[Pt(Se4)3].DMF, and beta-[PPh4]2[Pt(Se4)3] have been prepared from the reaction of the appropriate metal xanthate with Li2Sc and Se in DMF. The [PPh4]2[Pt(Se4)2] compound was isolated from the reduction of alpha-[PPh4]2[Pt(Se4)3].DMF with LiBEt3H in DMF. In [NEt4]5[2Pd(Se4)2.1/2Pd(Se5)2] the two independent [Pd(Se4)2]2- anions have a Pd atom chelated by two Se-4(2)-chains in slightly distorted square-planar coordination. In the [Pd(Se5)]2- anion the Pd center is in a square-planar coordination being chelated by two Se-5(2)-ligands. Both the alpha- and beta-[Pt(Se4)3]2-anions have an octahedral Pt atom chelated by three Se4(2)-chains. The conformation of the chains around the Pt atom is DELTAlambdalambdadelta (or LAMBDAdeltadeltalambda) in the alpha-anion and DELTAlambdadeltadelta (or LAMBDAdeltalambdalambda) in the beta-anion. The [Pt(Se4)2]2- anion is similar in geometry to the two [Pd(Se4)2]2- anions. Se-77 NMR resonances for these ions (delta, ppm): [Pd(Se4)2]2-, 758,893;[Pd(Se5)2]2-, 509,647,875; [Pt(Se4)3]2-, 680, 790; [Pt(Se4)2]2-, 642, 747. The Pt species exhibit the following Pt-195 NMR resonances (delta, ppm): [Pt(Se4)3]2-, -4217; [Pt(Se4)2]2-, -4568. Unit cell data: [NEt4]5[2Pd(Se4)2.1/2Pd(Se5)2], space group C-2h(5)-P2(1)/n, a = 26.965(5) angstrom, b = 10.543(2) angstrom, c = 26.580(5) angstrom, beta = 106.62(3)-degrees, V = 7241(2) angstrom3, Z = 4 (-163-degrees-C); alpha-[PPh4]2[Pt(Se4)3].DMF, space group C(i)1-P1BAR, a = 10.066(2) angstrom, b = 16.383(3) angstrom, c = 17.253(3) angstrom, alpha = 83.08(3)-degrees, beta = 86.41(3)-degrees, gamma = 86.24(3)-degrees, V = 2814(1) angstrom3, Z = 2 (-163-degrees-C); beta-[PPh4]2[Pt(Se4)3], space group C-2h(5)-P2(1)/c, a = 13.167(3) angstrom, b = 11.511(2) angstrom, c = 34.428(7) angstrom, beta = 98.45(3)-degrees, V = 5161(2) angstrom3, Z = 4 (-163-degrees-C); [PPh4]2[Pt(Se4)2], space group C-2(2)-P2(1), a = 10.974(2) angstrom, b = 15.314(3) angstrom, c = 14.180(3) angstrom, beta = 92.03(3)-degrees, V = 2382(1) angstrom3, Z = 2 (-163-degrees-C).