The complex chloride, Pd(Ph2Pqn)2Cl2 (Ph2Pqn = 8-(diphenylphosphino)quinoline), crystallized either in yellow plates (1a: from CH2Cl2/Et2O) or in orange needles (1b: from MeOH/Et2O). The corresponding bromide, Pd(Ph2Pqn)2Br2, initially deposited as yellow block crystals (2a) from MeOH/Et2O, turned to orange prisms (2b) on standing in the mother liquor. The X-ray crystallographic analyses of 1a and 2a revealed that two Cl- and Br- anions, respectively, were located above and below the square-planar Pd11 coordination plane of cis(P)-[Pd(Ph2Pqn)2]2+. Although the distances of Pd⋯Cl (3.262(3) and 3.386(3) A) and Pd⋯Br (3.432(2) and 3.505(2) Å) in 1a and 2a, respectively, were too long for a bonding interaction between Pd11 and X-, weak Pd 11⋯X~ charge-transfer interactions seem to be responsible for the yellow colors of these crystals. In contrast, in 2b, the Pd11 formed an elongated square-pyramidal five-coordinate complex, [Pd(Ph 2Pqn)2Br]+, with a somewhat long Pd-Br bond (3.0136(8) A) at the apical position. The crystal structure of Pd(Ph 2Pqn)2ClBF4 (4) revealed that the Pd 11 center in 4 took an extremely distorted square-planar coordination geometry with the Pd-Cl bond of 2.375(2) Å, while one of the Ph 2Pqn ligands coordinated through only P;cis(P)-[PdCl(Ph 2Pqn-κP,N)(Ph2Pqn-κP)]BF4.
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