2 research outputs found
Computational and Experimental Study on Selective sp<sup>2</sup>/sp<sup>3</sup> or Vinylic/Aryl Carbon–Hydrogen Bond Activation by Platinum(II): Geometries and Relative Stability of Isomeric Cycloplatinated Compounds
Cyclometalating
ligands 6-(1-phenylethyl)-2,2′-bipyridine
(<b>L4</b>), 6-(1-phenylvinyl)-2,2′-bipyridine (<b>L5</b>), and 6-(prop-1-en-2-yl)-2,2′-bipyridine (<b>L6</b>) were synthesized by the Negishi coupling of 6-bromo-2,2′-bipyridine
with the corresponding organozinc reagents. The reaction of <b>L4</b> with K<sub>2</sub>PtCl<sub>4</sub> produced only the cycloplatinated
compound <b>4a</b> via sp<sup>2</sup> C–H bond activation.
The reactions of <b>L5</b> and <b>L6</b> produced exclusively
the cycloplatinated compounds <b>5b</b> and <b>6a</b>,
respectively, via vinylic C–H bond activation. DFT calculations
were performed on 12 possible cycloplatination products from the reaction
of <i>N</i>-alkyl-<i>N</i>-phenyl-2,2′-bipyridin-6-amine
(alkyl = methyl (<b>L1</b>), ethyl (<b>L2</b>), and isopropyl
(<b>L3</b>)) and <b>L4</b>–<b>L6</b>. The
results show that compounds <b>1b</b>–<b>3b</b> resulting from the sp<sup>3</sup> C–H bond activation of <b>L1</b>–<b>L3</b> are thermodynamic products, and
their relative stability is attributed to the planar geometry that
allows for a better conjugation. Similar reasoning also applies to
the stability of products from vinylic C–H bond activation
of <b>L5</b> and <b>L6</b>. The relative stability of
isomeric cycloplatinated compounds <b>4a</b> and <b>4b</b> may be due to the different strengths of C–Pt bonds. The
steric interaction is the major cause of severe distortion from a
planar coordination geometry in the cycloplatinated compounds, which
leads to instability of the corresponding cyclometalated products
and a higher kinetic barrier for C–H bond activation
Computational and Experimental Study on Selective sp<sup>2</sup>/sp<sup>3</sup> or Vinylic/Aryl Carbon–Hydrogen Bond Activation by Platinum(II): Geometries and Relative Stability of Isomeric Cycloplatinated Compounds
Cyclometalating
ligands 6-(1-phenylethyl)-2,2′-bipyridine
(<b>L4</b>), 6-(1-phenylvinyl)-2,2′-bipyridine (<b>L5</b>), and 6-(prop-1-en-2-yl)-2,2′-bipyridine (<b>L6</b>) were synthesized by the Negishi coupling of 6-bromo-2,2′-bipyridine
with the corresponding organozinc reagents. The reaction of <b>L4</b> with K<sub>2</sub>PtCl<sub>4</sub> produced only the cycloplatinated
compound <b>4a</b> via sp<sup>2</sup> C–H bond activation.
The reactions of <b>L5</b> and <b>L6</b> produced exclusively
the cycloplatinated compounds <b>5b</b> and <b>6a</b>,
respectively, via vinylic C–H bond activation. DFT calculations
were performed on 12 possible cycloplatination products from the reaction
of <i>N</i>-alkyl-<i>N</i>-phenyl-2,2′-bipyridin-6-amine
(alkyl = methyl (<b>L1</b>), ethyl (<b>L2</b>), and isopropyl
(<b>L3</b>)) and <b>L4</b>–<b>L6</b>. The
results show that compounds <b>1b</b>–<b>3b</b> resulting from the sp<sup>3</sup> C–H bond activation of <b>L1</b>–<b>L3</b> are thermodynamic products, and
their relative stability is attributed to the planar geometry that
allows for a better conjugation. Similar reasoning also applies to
the stability of products from vinylic C–H bond activation
of <b>L5</b> and <b>L6</b>. The relative stability of
isomeric cycloplatinated compounds <b>4a</b> and <b>4b</b> may be due to the different strengths of C–Pt bonds. The
steric interaction is the major cause of severe distortion from a
planar coordination geometry in the cycloplatinated compounds, which
leads to instability of the corresponding cyclometalated products
and a higher kinetic barrier for C–H bond activation