4 research outputs found
Multinuclear Solid-State NMR and DFT Studies on Phosphanido-Bridged Diplatinum Complexes
Multinuclear (<sup>31</sup>P, <sup>195</sup>Pt, <sup>19</sup>F)
solid-state NMR experiments on (<i>n</i>Bu<sub>4</sub>N)<sub>2</sub>[(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>PtÂ(Îź-PPh<sub>2</sub>)<sub>2</sub>PtÂ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>] (<b>1</b>), [(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>PtÂ(Îź-PPh<sub>2</sub>)<sub>2</sub>PtÂ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>]Â(<i>PtâPt</i>) (<b>2</b>), and <i>cis</i>-PtÂ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(PHPh<sub>2</sub>)<sub>2</sub> (<b>3</b>) were carried out under cross-polarization/magic-angle-spinning
conditions or with the cross-polarization/CarrâPurcell MeiboomâGill
pulse sequence. Analysis of the principal components of the <sup>31</sup>P and <sup>195</sup>Pt chemical shift (CS) tensors of <b>1</b> and <b>2</b> reveals that the variations observed comparing
the isotropic chemical shifts of <b>1</b> and <b>2</b>, commonly referred to as âring effectâ, are mainly
due to changes in the principal components oriented along the direction
perpendicular to the Pt<sub>2</sub>P<sub>2</sub> plane. DFT calculations
of <sup>31</sup>P and <sup>195</sup>Pt CS tensors confirmed the tensor
orientation proposed from experimental data and symmetry arguments
and revealed that the different values of the isotropic shieldings
stem from differences in the paramagnetic and spinâorbit contributions
Oxidatively Induced PâO Bond Formation through Reductive Coupling between Phosphido and Acetylacetonate, 8âHydroxyquinolinate, and Picolinate Groups
The
dinuclear anionic complexes [NBu<sub>4</sub>]Â[(R<sub>F</sub>)<sub>2</sub>M<sup>II</sup>(Îź-PPh<sub>2</sub>)<sub>2</sub>Mâ˛<sup>II</sup>(N<sup>â§</sup>O)] (R<sub>F</sub> = C<sub>6</sub>F<sub>5</sub>. N<sup>â§</sup>O = 8-hydroxyquinolinate, hq; M = Mâ˛
= Pt <b>1</b>; Pd <b>2</b>; M = Pt, MⲠ= Pd, <b>3</b>. N<sup>â§</sup>O = <i>o</i>-picolinate,
pic; M = Pt, MⲠ= Pt, <b>4</b>; Pd, <b>5</b>) are
synthesized from the tetranuclear [NBu<sub>4</sub>]<sub>2</sub>[{(R<sub>F</sub>)<sub>2</sub>PtÂ(Îź-PPh<sub>2</sub>)<sub>2</sub>MÂ(Îź-Cl)}<sub>2</sub>] by the elimination of the bridging Cl as AgCl in acetone,
and coordination of the corresponding <i>N</i>,<i>O</i>-donor ligand (<b>1</b>, <b>4</b>, and <b>5</b>) or connecting the fragments â<i>cis</i>-[(R<sub>F</sub>)<sub>2</sub>MÂ(Îź-PPh<sub>2</sub>)<sub>2</sub>]<sup>2â</sup>â and âMâ˛(N<sup>â§</sup>O)â (<b>2</b> and <b>3</b>). The electrochemical oxidation of the
anionic complexes <b>1</b>â<b>5</b> occurring under
HRMSÂ(+) conditions gave the cations [(R<sub>F</sub>)<sub>2</sub>MÂ(Îź-PPh<sub>2</sub>)<sub>2</sub>Mâ˛(N<sup>â§</sup>O)]<sup>+</sup>, presumably endowed with a MÂ(III),Mâ˛(III) core. The oxidative
addition of I<sub>2</sub> to the 8-hydroxyquinolinate complexes <b>1</b>â<b>3</b> triggers a reductive coupling between
a PPh<sub>2</sub> bridging ligand and the <i>N</i>,<i>O</i>-donor chelate ligand with formation of a PâO bond
and ends up in complexes of platinumÂ(II) or palladiumÂ(II) of formula
[(R<sub>F</sub>)<sub>2</sub>M<sup>II</sup>(Îź-I)Â(Îź-PPh<sub>2</sub>)ÂMâ˛<sup>II</sup>(<i>P</i>,<i>N</i>-PPh<sub>2</sub>hq)], M = MⲠ= Pt <b>7</b>, Pd <b>8</b>; M = Pt, MⲠ= Pd, <b>9</b>. Complexes <b>7</b>â<b>9</b> show a new Ph<sub>2</sub>P-OC<sub>9</sub>H<sub>6</sub>N (Ph<sub>2</sub>P-hq) ligand bonded to the metal
center in a <i>P</i>,<i>N</i>-chelate mode. Analogously,
the addition of I<sub>2</sub> to solutions of the <i>o</i>-picolinate complexes <b>4</b> and <b>5</b> causes the
reductive coupling between a PPh<sub>2</sub> bridging ligand and the
starting <i>N</i>,<i>O</i>-donor chelate ligand
with formation of a PâO bond, forming Ph<sub>2</sub>P-OC<sub>6</sub>H<sub>4</sub>NO (Ph<sub>2</sub>P-pic). In these cases, the
isolated derivatives [NBu<sub>4</sub>]Â[(Ph<sub>2</sub>P-pic)Â(R<sub>F</sub>)ÂPt<sup>II</sup>(Îź-I)Â(Îź-PPh<sub>2</sub>)ÂM<sup>II</sup>(R<sub>F</sub>)ÂI] (M = Pt <b>10</b>, Pd <b>11</b>) are anionic, as a consequence of the coordination of the resulting
new phosphane ligand (Ph<sub>2</sub>P-pic) as monodentate <i>P</i>-donor, and a terminal iodo group to the M atom. The oxidative
addition of I<sub>2</sub> to [NBu<sub>4</sub>]Â[(R<sub>F</sub>)<sub>2</sub>Pt<sup>II</sup>(Îź-PPh<sub>2</sub>)<sub>2</sub>Pt<sup>II</sup>(acac)] (<b>6</b>) (acac = acetylacetonate) also results
in a reductive coupling between the diphenylphosphanido and the acetylacetonate
ligand with formation of a PâO bond and synthesis of the complex
[NBu<sub>4</sub>]Â[(R<sub>F</sub>)<sub>2</sub>Pt<sup>II</sup>(Îź-I)Â(Îź-PPh<sub>2</sub>)ÂPt<sup>II</sup>(Ph<sub>2</sub>P-acac)ÂI] (<b>12</b>).
The transformations of the starting complexes into the products containing
the PâO ligands passes through mixed valence MÂ(II),Mâ˛(IV)
intermediates which were detected, for M = MⲠ= Pt, by spectroscopic
and spectrometric measurements
Formation of PâC Bond through Reductive Coupling between Bridging Phosphido and Benzoquinolinate Groups. Isolation of Complexes of the Pt(II)/Pt(IV)/Pt(II) Sequence
The rational synthesis of dinuclear asymmetric phosphanido
derivatives
of palladium and platinumÂ(II), [NBu<sub>4</sub>]Â[(R<sub>F</sub>)<sub>2</sub>MÂ(Îź-PPh<sub>2</sub>)<sub>2</sub>Mâ˛(Îş<sup>2</sup>,<i>N</i>,<i>C</i>-C<sub>13</sub>H<sub>8</sub>N)] (R<sub>F</sub> = C<sub>6</sub>F<sub>5</sub>; M = Mâ˛
= Pt, <b>1</b>; M = Pt, MⲠ= Pd, <b>2</b>; M =
Pd, MⲠ= Pt, <b>3</b>; M = MⲠ= Pd, <b>4</b>), is described. Addition of I<sub>2</sub> to <b>1</b>â<b>4</b> gives complexes [(R<sub>F</sub>)<sub>2</sub>M<sup>II</sup>(Îź-PPh<sub>2</sub>)Â(Îź-I)ÂPd<sup>II</sup>{PPh<sub>2</sub>(C<sub>13</sub>H<sub>8</sub>N)}] (M = MⲠ= Pt, <b>6</b>; M = Pt, MⲠ= Pd, <b>7</b>; M = MⲠ= Pd, <b>8</b>; M = Pd, MⲠ= Pt <b>10</b>) which contain the
aminophosphane PPh<sub>2</sub>(C<sub>13</sub>H<sub>8</sub>N) ligand
formed through a Ph<sub>2</sub>P/C<sup>â§</sup>N reductive coupling
on the mixed valence MÂ(II)âMâ˛(IV) [NBu<sub>4</sub>]Â[(R<sub>F</sub>)<sub>2</sub>M<sup>II</sup>(Îź-PPh<sub>2</sub>)<sub>2</sub>Mâ˛<sup>IV</sup>(Îş<sup>2</sup>,<i>N</i>,<i>C</i>- C<sub>13</sub>H<sub>8</sub>N)ÂI<sub>2</sub>] complexes,
which were identified for M<sup>II</sup> = Pd, Mâ˛<sup>IV</sup> = Pt (<b>9</b>), and isolated for M<sup>II</sup> = Pt, Mâ˛<sup>IV</sup> = Pt (<b>5</b>). Complex <b>5</b> showed an
unusual dynamic behavior consisting in the exchange of two phenyl
groups bonded to different P atoms, as well as a âthrough spaceâ
spinâspin coupling between <i>ortho</i>-F atoms of
the pentafluorophenyl rings
Sulfur-Assisted Phenyl Migration from Phosphorus to Platinum in PtW<sub>2</sub> and PtMo<sub>2</sub> Clusters Containing Thioether-Functionalized Short-Bite Ligands of the Bis(diphenylphosphanyl)amine-Type
The
reactivity of dichloroplatinumÂ(II) complexes containing thioether-functionalized
bisÂ(diphenylÂphosphanyl)Âamines of formula (Ph<sub>2</sub>P)<sub>2</sub>NÂ(CH<sub>2</sub>)<sub>2</sub>SR (R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>, CH<sub>2</sub>Ph) toward group
6 carbonylmetalates NaÂ[MÂ(CO)<sub>3</sub>Cp] (M = Mo or W, Cp = cyclopentadienyl)
was explored. Reactions with two or more equivalents of NaÂ[MÂ(CO)<sub>3</sub>Cp] (M = Mo or W) afforded the trinuclear complexes of general
formula [PtPhÂ{MÂ(CO)<sub>3</sub>Cp}Â{Îź-<i>P</i>(Ph)ÂNÂ(CH<sub>2</sub>CH<sub>2</sub><i>S</i>R)Â(<i>P</i>Ph<sub>2</sub>)-Îş<sup>3</sup><i>P</i>,<i>P</i>,<i>S</i>}ÂMÂ(CO)<sub>2</sub>Cp] (<b>3</b> M = Mo, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>4</b> M = Mo, R = CH<sub>2</sub>Ph; <b>9</b> M = W, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>10</b> M = W, R = CH<sub>2</sub>Ph), the structure of which consists of a six-membered platinacycle
condensed with a four-membered MâPâNâP cycle, together with small amounts of isomeric PtM<sub>2</sub> clusters
[PtM<sub>2</sub>(CO)<sub>5</sub>Cp<sub>2</sub>Â{(Ph<sub>2</sub>P)<sub>2</sub>NÂ(CH<sub>2</sub>CH<sub>2</sub>SR)-Îş<sup>2</sup><i>P</i>,<i>P</i>}] (<b>5</b> M
= Mo, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>6</b> M = Mo, R = CH<sub>2</sub>Ph; <b>11</b> M = W, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>12</b> M = W, R = CH<sub>2</sub>Ph) in which the ligand (Ph<sub>2</sub>P)<sub>2</sub>NR solely
chelates the Pt atom or bridges an MâPt bond as in [PtM<sub>2</sub>(CO)<sub>5</sub>Cp<sub>2</sub>Â{Îź-(Ph<sub>2</sub>P)<sub>2</sub>NÂ(CH<sub>2</sub>CH<sub>2</sub>SR)-Îş<sup>2</sup><i>P</i>,<i>P</i>}] (<b>7</b> M
= Mo, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>8</b> M = Mo, R = CH<sub>2</sub>Ph; <b>13</b> M = W, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>14</b> M = W, R = CH<sub>2</sub>Ph). The synthesis of the trinuclear complexes <b>3</b>, <b>4</b>, <b>9</b>, and <b>10</b> entails an
unexpected P-phenyl bond cleavage reaction and phenyl migration onto
Pt. When only 1 equiv of NaÂ[MÂ(CO)<sub>3</sub>Cp] (M = Mo or W) was
used, the heterodinuclear products of monosubstitution [PtClÂ{MÂ(CO)<sub>3</sub>Cp}Â{Ph<sub>2</sub>PNÂ(R)ÂPPh<sub>2</sub>-<i>P</i>,<i>P</i>}] (<b>15</b> M = Mo, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>16</b> M = Mo, R = CH<sub>2</sub>Ph; <b>17</b> M = W, R = (CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>; <b>18</b> M = W, R = CH<sub>2</sub>Ph) were obtained,
which are the precursors to the bicyclic products <b>3</b>, <b>4</b>, <b>9</b>, and <b>10</b>, respectively. Density
functional calculations were performed to study the thermodynamics
of the formation of all the new complexes, to evaluate the relative
stabilities of the isomeric chelated and bridged forms, and to trace
the mechanism of formation of the phosphanido-bridged products <b>3</b>, <b>4</b>, <b>9</b>, and <b>10</b>. It was concluded that PtÂ(II)
complexes containing a <i>thioether</i>-functionalized short-bite
ligand, [PtCl<sub>2</sub>{Ph<sub>2</sub>PÂNÂ(R)ÂPPh<sub>2</sub>}], react with NaÂ[MÂ(CO)<sub>3</sub>Cp] to yield first heterodinuclear
PtâM and then heterotrinuclear PtM<sub>2</sub> complexes resulting
from the activation of a PâC bond in one of the PPh<sub>2</sub> groups and phenyl migration to Pt. The critical role of an intramolecular
thioether group was demonstrated