1. A Structural and Spectroscopic Investigation of Octahedral Platinum Bis(dithiolene)phosphine Complexes: Platinum Dithiolene Internal Redox Chemistry Induced by Phosphine Association.
- Author
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Chandrasekaran, P., Greene, Angelique F., Lillich, Karen, Capone, Stephen, Mague, Joel T., DeBeer, Serena, and Donahue, Janies P.
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MOLECULAR structure , *SPECTROMETRY , *OCTAHEDRAL molecules , *PHOSPHINE , *METAL complexes , *DITHIOLENES , *CHEMICAL reactions - Abstract
The complexes [Pt(mdt)2] (4; mdt = methyl dithiolene, [Me2C2S2]n-), [Pt(adt)2] (5; adt = p-anisyldithiolene, [(MeO-p-C6H4)2C2S2]2-), and [Pd(adt)2] (10) have been prepared in yields of ≥ 90% via transmetalation reactions with the corresponding [R2Sn(S2C2R'2)] complexes (R = "Bu, R' = Me; R = Me, R' = C6H4-p-OMe, 3). Intrahgand C--S and C--CchclaIe bond lengths (~1.71 and ~1.40 A, respectively) obtained by X-ray crystallography show these compounds to be comprised of radical monoanions mdt*- and adt*- . The six-coordinate octahedral adducts [Pt(adt)2(dppe)J [6; dppe = 1,2-bis(diphenylphosphino)ethane], trans-[Pt(adt)2(PMe3)2] (8), and frans-[Pt(mdt)2(PMe3)2] (9) have also been prepared, and crystal structures reveal dithiolene ligands that are fully reduced ene-l,2-dithiolates (C--S and C--Cchelate = ~1.77 and 1.35 A, respectively). Reduction of the dithiolene ligand thus occurs to accommodate the +IV oxidation state typical of octahedral sixcoordinate platinum. The cyclic voltammogram of 5 shows twofully reversible reductions at --0.11 and --0.84 V in CH2C12 (vs Ag/AgCl), attributed to successive (adt*- + e- → adt2-) processes, and a reversible oxidation at +1.01 V. The cyclic voltammogram of 9 shows two reversible oxidations at +0.38 and +0.86 V, which are assigned as successive (adt2- → adt*- + e-) oxidations. Consistent with their formulation as having fully reduced dithiolene ligands, the UV--vis spectra for 6, 8, and 9 show no low-energy absorptions below 700 nm, and the S K-edge XAS spectra of 6 and 8 show dithiolene sulfur that is reduced relative to that in 5. The introduction of PMe3 to 10 did not produce the palladium analogue of 8 but rather [Pd(adt)(PMe3)2] (11) . The reaction of [PdCl2(PPh3)2] with Li2(mdt) produced a mixture of [Pd(mdt)(PPh3)2] (12, 20%) and [(Ph3P)Pd(p-l,2-mdt- S,S':S)2Pd(PPh3)] (13, 28%), with the latter having C2 symmetry with a Pd2S2 core structure folded along the S S axis. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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