Metallosulfoxides and -sulfones: Sulfur Oxygenates of [1,5-Bis(2-mercaptoethyl)-1,5-diazacyclooctanato]palladium(II)
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Successive sulfur-site oxygenation of the dithiolate complex [1,5-bis(mercaptoethyl)-1,5-diazacyclooctanato]-palladium(II), Pd-1, using H2O2 as an O atom source produced all but one member of the series of palladium(II) complexes containing sulfonate (metallosulfone) and sulfenate (metallosulfoxide) S-donor ligands: the monosul-foxide, PdS(=0)R or Pd-4; bis(sulfoxide), Pd(S(=O)R)2 or Pd-5; sulfone/sulfoxide, Pd(SO2R)S(=O)R or Pd-6; and the bis(sulfone) Pd(SO2R)2 or Pd-3 complex. A unique site selectivity for the addition of a second O atom from H2O2 to thiolate sulfur of Pd-4 producing the bis(sulfoxide), Pd-5, exclusively, precluded the preparation of the monosulfone complex, Pd(SO2R)SR or Pd-2, via that route. However, the dithiolate Pd-1 reacts with O2 photochemically in aprotic solvents, giving access to this last member of the series, Pd-2. Further reaction of Pd-2 with O2 under UV photolysis gives the bis(sulfone) complex, Pd-3. The oxygenates were characterized by various spectroscopies, electrochemistry, and X-ray crystallography. Mass spectrometry delineated a single O atom loss pathway for the sulfoxide species, while SO2 and O2 loss is found in sulfone cases. Electrochemical studies show that the addition of an O atom to a thiolate sulfur to create a sulfoxide S-donor results in a stabilization of the Pd1 oxidation state in the range 50–70 mV, while the addition of an O atom to a sulfoxide sulfur to create a sulfone S-donor results in greater stabilization of the Pd1 oxidation state in the range 190–220 mV. Complex Pd-2 crystallizes in the monoclinic P21/c (No. 14) space group with a = 8.362(11) Å, b = 12.102(9) Å, c = 12.990(14) Å, β = 101.39(9)°, V = 1289(2) Å3, and Z = 4. Complex Pd-4 crystallizes in the orthorombic P21212 space group with a = 12.210(2) Å, b = 15.931(4) Å, c = 6.802(2) Å, V = 1323.1(6) Å3, and Z = 4. Complex Pd-6 cocrystallizes with Pd-3 in the monoclinic C2/c space group with a = 15.862(5) Å,b = 8.146(2) Å, c = 21.812(9) Å, β= 107.82(2)°, V = 2683(2) Å3, and Z = 8. © 1995, American Chemical Society. All rights reserved.
author list (cited authors)
Tuntulani, T., Musie, G., Reibenspies, J. H., & Darensbourg, M. Y.