5-COORDINATION .8. LOW-SPIN TRANSITION METAL COMPLEXES WITH AN OPEN-CHAIN TETRADENTATE PHOSPHORUS-SULFUR LIGAND

The new open-chain tetradentate ligand 1,3-bis(diphenylphosphinopropylthio)propane, (C6H5)2P(CH2)3S(CH2)3P- (C6H5)2, forms five-coordinate [M(C33H38P2S2)X]ClO4 complexes (where M = Ni, Pd, Pt, Co), in addition to the squareplanar [M(C33H38P2S2)](ClO4)2 complexes (where M = Ni, Pd, Pt). Spectrophotometric titrations of the four-coordinate d8 complexes with iodide ion, as well as the conductance behavior of the isolated materials, substantiate formation of the M(C33H38P2S2)X+ complexes. The five-coordinate nickel(II) complexes are intensely purple and exhibit a trigonal-bipyramidal structure, whereas the five-coordinate palladium(II) and platinum(II) complexes are orange and apparently possess a square-pyramidal structure. All of these four- and five-coordinate d8 ions are diamagnetic. The analogous series of maroon, five-coordinate [Co(C33H38P2S2)X] Y complexes (where X = Cl, Br, I and Y = B(C6H4); X = Cl and Y = ClO4) possess one unpaired electron (μeff = 2.05 ± 0.08 BM). The magnetic and spectral properties of the different series of complexes are correlated principally with those of the bidentate phosphorus-sulfur ligand diphenyl(o-methylthiophenyl)- phosphine. © 1969, American Chemical Society. All rights reserved.