Photochemical and chemical oxidation of alpha-dimine-dithiolene metal complexes: insight into the role of the metal atom.
[Pd(bpy)(bdt)], 2 (bpy = 2,2'-bipyridine, bdt = 1,2-benzenedithiolate), was prepared in good yield by the reaction of bdtNa2 with [(bpy)PdCl2] in DMSO. The analogous nickel complex, 1, was prepared in a similar reaction using MeOH/CH2Cl2 and [(bpy)NiCl2.dmf]2. Both 1 (a = 7.9920(1) A, b = 11.4385(1) A, c = 16.1415(1) A, beta = 103.327(1) degrees, V = 1435.86(2) A3, Z = 4) and 2 (a = 8.1631(5) A, b = 11.4379(7) A, c = 16.2475(10) A, beta = 103.7010(10) degrees, V = 1473.84(12) A3, Z = 4) crystallize in the monoclinic space group P2(1)/c and are isostructural with their previously reported platinum analogue. In accord with the results observed for platinum but not nickel, photochemical oxidation of 2 in DMF provides the monosulfinate complex [Pd(bpy)(bdtO2)], 4, along with a minor amount of the corresponding disulfinate [Pd(bpy)(bdtO4)], 5, while chemical oxidation yields only the latter. 4 cocrystallizes with 5 in the monoclinic space group P2(1)/c (a = 8.026(3) A, b = 14.600(6) A, c = 13.371(3) A, beta = 101.80(3) degrees, V = 1533.8(9) A3, Z = 4) as does pure 5 (a = 8.5611(9) A, b = 14.4586(15) A, c = 13.3677(14) A, beta = 108.122(2) degrees, V = 1572.6(3) A3, Z = 4). Comparison of spectroscopic and electrochemical properties of the three complexes, [M(bpy)(bdt)], yields the following ordering for the energy of the HOMO: Pd < Ni < Pt. The observed reactivity patterns and the electronic data suggest that the "anomalous" reactivity of 1 be attributed to the greater relative flexibility of the coordination geometry for nickel(II) complexes rather than electronic differences such as the energies of the frontier orbitals.
Department of Chemistry, Box 571227, Georgetown University, Washington, DC 20057-1227, USA.
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Bachman