10.1021/ic0207000.s002
Richard D. Adams
Richard D.
Adams
Burjor Captain
Burjor
Captain
Wei Fu
Wei
Fu
Perry J. Pellechia
Perry J.
Pellechia
Dynamical Intramolecular Metal-to-Metal Ligand Exchange of Phosphine
and Thioether Ligands in Derivatives PtRu<sub>5</sub>(CO)<sub>16</sub>(μ<sub>6</sub>-C)
American Chemical Society
2003
PMe 2 Ph ligands
phosphine ligand
metal atoms
compound
NMR
PMe 2 Ph
2 S ligand
complexes PtRu 5
Ru atoms
PtRu 5
kcal
Δ G 298
CO
cal
isomer
carbido carbon atom
Derivatives PtRu 5
2 S ligands
isomerization
2003-04-05 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Dynamical_Intramolecular_Metal-to-Metal_Ligand_Exchange_of_Phosphine_and_Thioether_Ligands_in_Derivatives_PtRu_sub_5_sub_CO_sub_16_sub_sub_6_sub_-C_/3606969
The complexes PtRu<sub>5</sub>(CO)<sub>15</sub>(PMe<sub>2</sub>Ph)(μ<sub>6</sub>-C) (<b>2)</b>, PtRu<sub>5</sub>(CO)<sub>14</sub>(PMe<sub>2</sub>Ph)<sub>2</sub>(μ<sub>6</sub>-C) (<b>3</b>), PtRu<sub>5</sub>(CO)<sub>15</sub>(PMe<sub>3</sub>)(μ<sub>6</sub>-C) (<b>4</b>),
PtRu<sub>5</sub>(CO)<sub>14</sub>(PMe<sub>3</sub>)<sub>2</sub>(μ<sub>6</sub>-C) (<b>5</b>), and PtRu<sub>5</sub>(CO)<sub>15</sub>(Me<sub>2</sub>S)(μ<sub>6</sub>-C)<b> (6)</b> were obtained from the reactions of PtRu<sub>5</sub>(CO)<sub>16</sub>(μ<sub>6</sub>-C) (<b>1</b>) with the appropriate ligand. As determined by NMR spectroscopy, all the new complexes exist in solution
as a mixture of isomers. Compounds <b>2</b>, <b>3</b>, and <b>6</b> were characterized crystallographically. In all three compounds,
the six metal atoms are arranged in an octahedral geometry, with a carbido carbon atom in the center. The PMe<sub>2</sub>Ph
and Me<sub>2</sub>S ligands are coordinated to the Pt atom in <b>2</b> and <b>6</b>, respectively. In <b>3</b>, the two PMe<sub>2</sub>Ph ligands are
coordinated to Ru atoms. In solution, all the new compounds undergo dynamical intramolecular isomerization by
shifting the PMe<sub>2</sub>Ph or Me<sub>2</sub>S ligand back and forth between the Pt and Ru atoms. For compound <b>2</b>, Δ<i>H</i><sup>⧧</sup>= 15.1(3)
kcal/mol, Δ<i>S</i><sup>⧧</sup> = −7.7(9) cal/(mol·K), and Δ<i>G</i><sub>298</sub> = 17.4(6) kcal/mol for the transformation of the major isomer to
the minor isomer; for compound <b>4</b>, Δ<i>H</i><sup>⧧</sup> = 14.0(1) kcal/mol, Δ<i>S</i><sup>⧧</sup> = −10.7(4) cal/(mol·K), and Δ<i>G</i><sub>298</sub> = 17.2(2)
kcal/mol for the transformation of the major isomer to the minor isomer; for compound <b>6</b>, Δ<i>H</i><sup>⧧</sup> = 18(1) kcal/mol,
Δ<i>S</i><sup>⧧</sup> = 21(5) cal/(mol·K) and Δ<i>G</i><sub>298</sub> = 12(2) kcal/mol. The shifts of the Me<sub>2</sub>S ligand in <b>6</b> are significantly more
facile than the shifts for the phosphine ligand in compounds <b>2</b>−<b>5</b>. This is attributed to a more stable ligand-bridged
intermediate for the isomerizations of <b>6</b> than that for compounds <b>2</b>−<b>5</b>. The intermediate for the isomerization of <b>6</b>
involves a bridging Me<sub>2</sub>S ligand that can use two lone pairs of electrons for coordination to the metal atoms,
whereas a tertiary phosphine ligand can use only one lone pair of electrons for bridging coordination.