A Structural and Spectroscopic Investigation of Octahedral
Platinum Bis(dithiolene)phosphine Complexes: Platinum Dithiolene Internal
Redox Chemistry Induced by Phosphine Association
P. Chandrasekaran
Angelique
F. Greene
Karen Lillich
Stephen Capone
Joel T. Mague
Serena DeBeer
James P. Donahue
10.1021/ic501273b.s002
https://acs.figshare.com/articles/dataset/A_Structural_and_Spectroscopic_Investigation_of_Octahedral_Platinum_Bis_dithiolene_phosphine_Complexes_Platinum_Dithiolene_Internal_Redox_Chemistry_Induced_by_Phosphine_Association/2259457
The
complexes [Pt(mdt)<sub>2</sub>] (<b>4</b>; mdt = methyldithiolene,
[Me<sub>2</sub>C<sub>2</sub>S<sub>2</sub>]<sup><i>n</i>−</sup>), [Pt(adt)<sub>2</sub>] (<b>5</b>; adt = <i>p</i>-anisyldithiolene, [(MeO-<i>p</i>-C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>C<sub>2</sub>S<sub>2</sub>]<sup><i>n</i>−</sup>), and [Pd(adt)<sub>2</sub>] (<b>10</b>) have been prepared
in yields of ≥90% via transmetalation reactions with the corresponding
[R<sub>2</sub>Sn(S<sub>2</sub>C<sub>2</sub>R′<sub>2</sub>)]
complexes (R = <sup><i>n</i></sup>Bu, R′ = Me; R
= Me, R′ = −C<sub>6</sub>H<sub>4</sub>-<i>p</i>-OMe, <b>3</b>). Intraligand C–S and C–C<sub>chelate</sub> bond lengths (∼1.71 and ∼1.40 Å,
respectively) obtained by X-ray crystallography show these compounds
to be comprised of radical monoanions mdt<sup>•–</sup> and adt<sup>•–</sup>. The six-coordinate octahedral
adducts [Pt(adt)<sub>2</sub>(dppe)] [<b>6</b>; dppe = 1,2-bis(diphenylphosphino)ethane], <i>trans</i>-[Pt(adt)<sub>2</sub>(PMe<sub>3</sub>)<sub>2</sub>]
(<b>8</b>), and <i>trans</i>-[Pt(mdt)<sub>2</sub>(PMe<sub>3</sub>)<sub>2</sub>] (<b>9</b>) have also been prepared, and
crystal structures reveal dithiolene ligands that are fully reduced
ene-1,2-dithiolates (C–S and C–C<sub>chelate</sub> =
∼1.77 and 1.35 Å, respectively). Reduction of the dithiolene
ligand thus occurs to accommodate the +IV oxidation state typical
of octahedral six-coordinate platinum. The cyclic voltammogram of <b>5</b> shows two fully reversible reductions at −0.11 and
−0.84 V in CH<sub>2</sub>Cl<sub>2</sub> (vs Ag/AgCl), attributed
to successive (adt<sup>•–</sup> + e<sup>–</sup> → adt<sup>2–</sup>) processes, and a reversible oxidation
at +1.01 V. The cyclic voltammogram of <b>9</b> shows two reversible
oxidations at +0.38 and +0.86 V, which are assigned as successive
(adt<sup>2–</sup> → adt<sup>•–</sup> +
e<sup>–</sup>) oxidations. Consistent with their formulation
as having fully reduced dithiolene ligands, the UV–vis spectra
for <b>6</b>, <b>8</b>, and <b>9</b> show no low-energy
absorptions below 700 nm, and the S K-edge XAS spectra of <b>6</b> and <b>8</b> show dithiolene sulfur that is reduced relative
to that in <b>5</b>. The introduction of PMe<sub>3</sub> to <b>10</b> did not produce the palladium analogue of <b>8</b> but rather [Pd(adt)(PMe<sub>3</sub>)<sub>2</sub>] (<b>11</b>). The reaction of [PdCl<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>] with Li<sub>2</sub>(mdt) produced a mixture of [Pd(mdt)(PPh<sub>3</sub>)<sub>2</sub>] (<b>12</b>, 20%) and [(Ph<sub>3</sub>P)Pd(μ-1,2-mdt-<i>S</i>,<i>S</i>′:<i>S</i>)<sub>2</sub>Pd(PPh<sub>3</sub>)] (<b>13</b>, 28%),
with the latter having <i>C</i><sub>2</sub> symmetry with
a Pd<sub>2</sub>S<sub>2</sub> core structure folded along the S···S
axis.
2014-09-02 00:00:00
2C
Platinum Dithiolene Internal Redox Chemistry Induced
adt
XAS
Pt
C 2 symmetry
3P
cyclic voltammogram
8 show dithiolene sulfur
UV
Pd 2S core structure
IV oxidation state
dithiolene ligands
CH
6H
R 2Sn complexes
Phosphine AssociationThe complexes