Synthesis and characterisation of palladium(II) iodo complexes containing water soluble phosphine ligands.: Crystal structures of [PdI2(PTA-H)2][PtI3(PTA)]2 • 2H2O and trans-[PdI2(PTA)2]

The aqueous solution behaviour of the equilibrium related cis-[PdCl2(PTA)2] and [PdCl(PTA)3]Cl complexes has been investigated in the presence of acid and iodide ions. Several of the resulting species were identified and a reaction scheme accounting for identified complexes is proposed. The crystal structures of trans-[PdI2(PTA-H)(2)][PdI3(PTA)](2) (.) 2H(2)O (1) (PTA-H+ = protonated form of PTA) and trans- [PdI2(PTA)(2)] (2) are reported. The geometry around the Pd(II) metal centre in I (for both the cation and anion) and 2 is distorted square planar. The PTA ligands occupy a trans orientation in the cation of I and in complex 2. Compound I represents a rare example of a Pd(II) system wherein the cation:anion pair, in a 1:2 ratio, are both coordination complexes. It is the first d(8) Ni-triad square planar complex containing only one PTA ligand and only the second platinum group metal complex. For the cation in 1, the bond distances and angles are Pd(1)-P(1) = 2.2864(16) angstrom, Pd(1)-I(1) = 2.6216(7) angstrom, P(1)-Pd(1)-P(1)' = 180.00(7)degrees and P(1)-Pd(1)-I(1) = 87.62(4)degrees, while in the anion the bond distances are Pd(2)-P(2) = 2.2377(15) angstrom, Pd(2)-I(4) = 2.5961(13) angstrom Pd(2)-I(2) = 2.6328(13) angstrom, Pd(2)-I(3) = 2.6513(8) angstrom, while the angles are P(2)-Pd(2)-I(4) = 90.00(5)degrees, P(2)-Pd(2)-I(2) = 89.69(5)degrees I(4)-Pd(2)-I(2) = 179.57(2)degrees, P(2)-Pd(2)-I(3) = 175.19(4)degrees, I(4)-Pd(2)-I(3) = 90.29(4)degrees and I(2)-Pd(2)-I(3) = 90.05(4)degrees. Bond distances and angles of the coordination polyhedron in 2 are Pd-P = 2.327(3) angstrom, Pd-I = 2.5916(10) angstrom, P-Pd-I = 89.13(7)degrees and P-Pd-P = 180.00(13)degrees. The average effective- and Tolman cone angles for the two ligands, calculated from the crystallographic data, are 115 degrees and 117 degrees for PTA and PTA-H, respectively. (c) 2004 Published by Elsevier B.V.