METALLOSULFOXIDES AND METALLOSULFONES - SULFUR OXYGENATES OF [1,5-BIS(2-MERCAPTOETHYL)-1,5-DIAZACYCLOOCTANATO]PALLADIUM(II)

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 sulfinate (metallosulfone) and sulfenate (metallosulfoxide) S-donor ligands: the monosulfoxide, PdS(=O)R or Pd-4; bis(sulfoxide), Pd(S(=O)R)(2) or Pd-5; sulfone/sulfoxide, Pd(SO(2)R)S(=O)R or Pd-6; and the bis(sulfone) Pd(SO(2)R)(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(SO(2)R)SR or Pd-2, via that route. However, the dithiolate Pd-1 reacts with O-2 photochemically in aprotic solvents, giving access to this last member of the series, Pd-2. Further reaction of Pd-2 with O-2 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 O-2 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 Pdl 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 Pd-1 oxidation state in the range 190-220 mV. Complex Pd-2 crystallizes in the monoclinic P2(1)/c (No. 14) space group with a = 8.362(11) Angstrom, b = 12.102(9) Angstrom, c = 12.990(14) Angstrom, beta = 101.39(9)degrees, V = 1289(2) Angstrom(3) and Z = 4. Complex Pd-4 crystallizes in the orthorombic P2(1)2(1)2 space group with a 12.210(2) Angstrom, b = 15.931(4) Angstrom, c = 6.802(2) Angstrom, V = 1323.1(6) Angstrom(3), and Z = 4. Complex Pd-6 cocrystallizes with Pd-3 in the monoclinic C2/c space group with a 15.862(5) Angstrom, b = 8.146(2) Angstrom, c = 21.812(9) Angstrom, beta = 107.82(2)degrees, V = 2683(2) Angstrom(3), and Z = 8.